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Chronic pain as a symptom or a disease: the IASP Classification of Chronic Pain for the International Classification of Diseases (ICD-11)

Abstract

Chronic pain is a major source of suffering. It interferes with daily functioning and often is accompanied by distress. Yet, in the International Classification of Diseases, chronic pain diagnoses are not represented systematically. The lack of appropriate codes renders accurate epidemiological investigations difficult and impedes health policy decisions regarding chronic pain such as adequate financing of access to multimodal pain management. In cooperation with the WHO, an IASP Working Group has developed a classification system that is applicable in a wide range of contexts, including pain medicine, primary care, and low-resource environments. Chronic pain is defined as pain that persists or recurs for more than 3 months. In chronic pain syndromes, pain can be the sole or a leading complaint and requires special treatment and care. In conditions such as fibromyalgia or nonspecific low-back pain, chronic pain may be conceived as a disease in its own right; in our proposal, we call this subgroup "chronic primary pain." In 6 other subgroups, pain is secondary to an underlying disease: chronic cancer-related pain, chronic neuropathic pain, chronic secondary visceral pain, chronic posttraumatic and postsurgical pain, chronic secondary headache and orofacial pain, and chronic secondary musculoskeletal pain. These conditions are summarized as "chronic secondary pain" where pain may at least initially be conceived as a symptom. Implementation of these codes in the upcoming 11th edition of International Classification of Diseases will lead to improved classification and diagnostic coding, thereby advancing the recognition of chronic pain as a health condition in its own right.
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Narrative Review
Chronic pain as a symptom or a disease: the IASP
Classification of Chronic Pain for the International
Classification of Diseases (ICD-11)
Rolf-Detlef Treede
a,
*, Winfried Rief
b
, Antonia Barke
b
, Qasim Aziz
c
, Michael I. Bennett
d
, Rafael Benoliel
e
,
Milton Cohen
f
, Stefan Evers
g
, Nanna B. Finnerup
h,i
, Michael B. First
j
, Maria Adele Giamberardino
k
, Stein Kaasa
l,m,n
,
Beatrice Korwisi
b
, Eva Kosek
o
, Patricia Lavand’homme
p
, Michael Nicholas
q
, Serge Perrot
r
, Joachim Scholz
s
,
Stephan Schug
t,u
, Blair H. Smith
v
, Peter Svensson
w,x
, Johan W.S. Vlaeyen
y,z,aa
, Shuu-Jiun Wang
bb,cc
Abstract
Chronic pain is a major source of suffering. It interferes with daily functioning and often is accompanied by distress. Yet, in the International
Classification of Diseases, chronic pain diagnoses are not represented systematically. The lack of appropriate codes renders accurate
epidemiological investigations difficult and impedes health policy decisions regarding chronic pain such as adequate financing of access to
multimodal pain management. In cooperation with the WHO, an IASP Working Group has developed a classification system that is applicable in
a wide range of contexts, including pain medicine, primary care, and low-resource environments. Chronic pain is defined as pain that persists or
recurs for more than 3 months. In chronic pain syndromes, pain can be the sole or a leading complaint and requires special treatment and care.
In conditions such as fibromyalgia or nonspecific low-back pain, chronic pain may be conceived as a disease in its own right; in our proposal, we
call this subgroup “chronic primary pain.” In 6 other subgroups, pain is secondary to an underlying disease: chronic cancer-related pain, chronic
neuropathic pain, chronic secondary visceral pain, chronic posttraumatic and postsurgical pain, chronic secondary headache and orofacial
pain, and chronic secondary musculoskeletal pain. These conditions are summarized as “chronic secondary pain” where pain may at least
initially be conceived as a symptom. Implementation of these codes in the upcoming 11th edition of International Classification of Diseases will
lead to improved classification and diagnostic coding, thereby advancing the recognition of chronic pain as a health condition in its own right.
Keywords: Classification, ICD-11, Chronic pain, Symptom, Disease, Chronic primary pain, Chronic secondary pain, Functioning,
Diagnoses, Coding
1. Introduction
Pain is one of the most frequent causes for patients to seek
medical care.
28
Although mortality rates are highest for cardiac
infarction and stroke, infectious diseases, cancers, and diabetes,
chronic pain is a leading source of human suffering and
disability.
18
Pain itself and many diseases associated with chronic
pain are not immediately life threatening; people continue to live
Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.
R.-D. Treede, W. Rief, and A. Barke contributed equally to this manuscript.
a
Medical Faculty Mannheim of Heidelberg University, Mannheim, Germany,
b
Division of Clinical Psychology and Psychotherapy, Department of Psychology, Philipps-University Marburg,
Marburg, Germany,
c
Centre for Neuroscience and Trauma, Wingate Institute of Neurogastroenterology, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen
Mary, University of London, United Kingdom,
d
Academic Unit of Palliative Care, Univers ity of Leeds, Leeds, United Kingdom,
e
Department of Diagnostic Sciences, Rutgers School of Dental
Medicine,Rutgers,Newark,NJ,UnitedStates,
f
St Vincent’s Clinical School, UNSW, Sydney, New South Wales, Australia,
g
Department of Neurology, Krankenhaus Lindenbrunn, Faculty of
Medicine, University of M ¨unster,M ¨unster, Germany,
h
Department of Clinical Medicine,Danish Pain Research Center, Aarhus University, Aarhus, Denmark,
i
Department of Neurology, Aarhus
University Hospital, Aarhus, Denmark,
j
Department of Psychiatry, Columbia University, New York State Psychiatric Institute, New York, NY, United States,
k
Department of Medicine and
Science of Aging, CeSI-MeT, G D’Annunzio University of Chieti, Chieti, Italy,
l
European Palliative Care Research Centre (PRC),
m
Department of Oncology, Oslo University Hospital, Oslo,
Norway,
n
University of Oslo, Oslo, Norway,
o
Department of Clinical Neuroscience, Karolinska Institute, and Department of Neuroradiology, Karolinska University Hospital, Stockholm,
Sweden,
p
Department of Anesthesiology, Acute Postoperative Pain Service, Saint Luc Hospital, Catholic University of Louvain, Brussels, Belgium,
q
University of Sydney Medical School,
Sydney, Australia,
r
Pain Clinic, Hotel Dieu Hospital,Paris Descartes University, Paris, France,
s
Departments of Anesthesiology and Pharmacology, Columbia University, New York, NY, United
States,
t
Discipline of Anaesthesiology and Pain Medicine, Medical School, University of Western Australia, Perth, Australia,
u
Department of Anaesthesia and Pain Medicine, Royal Perth
Hospital, Perth, Australia,
v
Division of Population Health and Genomics, University of Dundee, Scotland,
w
Section of Clinical Oral Physiology, School of Dentistry, Aarhus University, Aarhus,
Denmark,
x
Department of Dental Medicine, Karolinska Institute, Huddinge, Sweden,
y
Research Group Health Psychology, University of Leuven, Leuven, Belgium,
z
TRACE, Center for
Translational Health Research, KU Leuven, Ziekenhuis Oost-Limburg, Genk, Belgium,
aa
Department of Clinical Psychological Science, Maastricht University, Maastricht, The Netherlands,
bb
The Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan,
cc
Brain Research Center and Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan
*Corresponding author. Departm ent of Neurophysiology, Centre for Biomedicine and Medical Technology Mannheim, Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-
Str.13–17, 68167 Mannheim, Germany. Tel.: 149 (0)621 383 71 400; fax: 149-(0)621 383 71 401. E-Mail address: Rolf-Detlef.Treede@medma.uni-heidelberg.de (R.-D. Treede).
Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the
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PAIN 160 (2019) 19–27
©2018 International Association for the Study of Pain
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Copyright Ó2018 by the International Association for the Study of Pain. Unauthorized reproduction of this article is prohibited.
with their pain, and hence, these conditions are common in both
developed and developing countries.
8,11
The Global Burden of
Disease Study 2013 evaluated “years lived with disability” (YLDs:
the prevalence multiplied by a disability-weighting factor) for
a broad range of diseases and injuries in 188 countries.
34
The
single greatest cause of YLDs around the world was chronic low-
back pain, followed by major depressive disorder. Other frequent
causes of YLDs include chronic neck pain, migraine, osteoar-
thritis, other musculoskeletal disorders, and medication overuse
headache.
Yet, in the International Classification of Diseases (ICD), chronic
pain diagnoses are not represented systematically.
13,15,35
In
many modern health care systems, referral for specific treatment
such as multimodal pain management is dependent on suitable
ICD codes as indications. The lack of appropriate codes
contributes to the paucity of clearly defined treatment pathways
for patients with chronic pain. Some pain specialists have argued
for recognition of chronic pain as a disease in its own right (for
a review see Ref. 33), whereas others have argued against this.
Recognition of migraine as a primary headache disorder has been
a crucial step towards including the International Headache
Classification of the International Headache Society into ICD.
21
Similarly, conditions such as fibromyalgia or complex regional
pain syndrome may qualify for classification as primary pain
disorders. On the other hand, chronic pain may be secondary to
osteoarthritis or diabetic polyneuropathy, where it may at least
initially be considered a symptom. In either case, chronic pain is
a long-term condition that requires special treatment and care.
Pain management should be guided by some measures of
patient-reported severity of this long-term condition. In acute pain
management, a level of “no more than mild pain” was established
as treatment goal.
29
Comparison of the epidemiology of “any,”
“significant,” and “severe” chronic pain indicated progressively
more marked adverse associations with employment status,
interference with daily activities, and general health.
41
Thus,
a future classification of chronic pain should also include an
option to code pain severity, which refers not just to pain intensity,
but also to distress and disability.
A systematic classification of chronic pain was developed by
a task force of the International Association for the Study of Pain
(IASP).
45
This classification distinguishes chronic primary and
chronic secondary pain syndromes, integrates existing pain
diagnoses including headaches, and provides precise definitions
and further characteristic features of the respective diagnoses
according to the content model of the WHO for ICD-11, including
the severity of pain, its temporal course, and evidence for
psychological and social factors. These pain diagnoses have
been implemented in the 11th version of ICD that was released by
WHO in June 2018.
2. Methods
The IASP, an NGO in official relationship with the WHO, contacted
the WHO in 2012 with respect to developing a new and pragmatic
classification of chronic pain for the upcoming 11th revision of the
ICD. The goal was to create a classification system that is applicable
in clinical settings for specialized pain management and in primary
care. A Task Force for the Classification of Chronic Pain was formed
by recruiting pain experts from around the globe (http://www.iasp-
pain.org/Advocacy/icd.aspx?ItemNumber55234&navItemNum-
ber55236), soliciting recommendations from IASP special interest
groups and topical advisory groups of other ICD-11 sections. The
co-chairs of the Task Force (W.R. and R.-D.T.) were in regular
contact with WHO representatives. The overall structure of the
chronic pain classification was developed by group consensus at the
first face-to-face meeting and by plenary phone conferences.
Subsequently, the subtopics were assigned to 7 smaller author
teams moderated by A.B.; overlaps between subtopics (eg, chronic
neuropathic pain after cancer treatment) were resolved through e-
mail and phone conferences and definitions established by
consensus among the teams concerned, and guidelines for
classification in overlapping fields were specified.
The ICD-11 development process requires the generation of
content models for each diagnostic entity, which contain
definitions, diagnostic criteria, and synonyms as well as state of
the art scientific information about the respective entity.
52
The
content models were developed by the 7 author teams and were
then entered as children of the appropriate parent entities through
the WHO proposal platform. Preliminary versions of the classi-
fication were published
45
presented at international conferences
(World Congress on Pain 2016, European Pain Congress 2017)
and were open to public comment through the IASP web site and
the WHO proposal platform. An early version of the classification
underwent pilot ecological field testing in 4 countries in 2016.
3
The prefinal version was further subjected to the official
international field testing of the WHO through the IASP web site.
49
3. Results
Chronic pain was defined previously as pain that persists past
normal healing time
7
and hence lacks the acute warning function
of physiological nociception. The concept of persistence beyond
normal healing may apply to pain after surgery and the concept of
lack of warning function to migraine headaches, but these
concepts are difficult to verify in other conditions such as chronic
musculoskeletal or neuropathic pains. Hence, a purely temporal
criterion was chosen: chronic pain is pain that lasts or recurs for
longer than 3 months.
45
The chronic pain definition was cast into the format of the
“content models” as required by WHO for ICD-11 and was
entered into what is called the “foundation layer of ICD-11.” The
foundation layer is the set of all entities represented in the ICD-11,
which is continually updated and expanded, and where each is
assigned a unique identifier (chronic pain: http://id.who.int/icd/
entity/1581976053). Chronic pain is the “parent code” for 7 other
codes that comprise the most common clinically relevant groups
of chronic pain conditions (Fig. 1): (1) chronic primary pain; (2)
chronic cancer-related pain; (3) chronic postsurgical or post-
traumatic pain; (4) chronic neuropathic pain; (5) chronic
secondary headache or orofacial pain; (6) chronic secondary
visceral pain; and (7) chronic secondary musculoskeletal pain.
There is some overlap between these groups of chronic pain
conditions (eg, neuropathic pain caused by cancer or its treatment)
and between the pain codes and other existing codes in ICD-11 (eg,
chronic headaches). The ICD-11 solves the problem of entities that
belong to several fields (eg, stroke as both a cardiovascular and
a neurological disorder) by so-called “multiple parenting.” Multiple
parenting allows that one definition (the child) may be accessed from
more than one higher level category (parent), but the child will have
the same unique definition under both parent codes. This feature
allows for more flexibility than in previous versions of ICD,foran
example, see Figure 2.
So-called “linearizations” are subsets of the foundation layer
that are used for statistical and coding purposes. The most
important linearization is the “mortality and morbidity lineariza-
tion.” The new ICD category for “chronic pain” and its 7
subcategories are part of this linearization, where they are listed
in the chapter that describes “certain symptoms, for which
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supplementary information is provided, that represent important
problems in medical care in their own right” (Chapter 21). A
“frozen version” of the mortality and morbidity linearization for
quality control through field testing was made available in April
2017 and was updated in April 2018; the codes in linearizations
may change over time as ICD-11 evolves and is maintained by the
WHO (chronic pain was MJ60 in 2017 and MG30 in 2018). A
“frozen version for implementation” has been published on June
18, 2018, and is scheduled for voting by the World Health
Assembly in May 2019.
50
After endorsement, countries around
the world are expected to report their health statistics using ICD-
11 from 2022 onward.
3.1. Chronic primary pain syndromes
Chronic primary pain is defined as pain in one or more
anatomical regions that persists or recurs for longer than 3
months and is associated with significant emotional distress or
functional disability (interference with activities of daily life and
participation in social roles) and that cannot be better accounted
for by another chronic pain condition.
30
This is a new definition,
which applies to chronic pain syndromes that are best
conceived as health conditions in their own right.
33
As illustrated
in Figure 1, diagnostic entities within this category are
subdivided into chronic widespread pain (eg, fibromyalgia),
complex regional pain syndromes, chronic primary headache
and orofacial pain (eg, chronic migraine or temporomandibular
disorder), chronic primary visceral pain (eg, irritable bowel
syndrome), and chronic primary musculoskeletal pain (eg,
nonspecific low-back pain). Chronic secondary pain syn-
dromes
2,4,6,32,38,39
are important differential diagnoses (see
also section 3.2). Chronic primary headaches are cross-
referenced in this section making use of the “multiple parenting”
option of ICD-11, which means that chronic migraine is listed in
both the headache section and the chronic pain section. The
term “chronic primary pain” may sound unusual but is
consistent with language used in other parts of ICD-11.The
recently proposed definition of “nociplastic pain” may describe
some of the underlying mechanisms.
26
Figure 1. Structure of the IASP Classification of Chronic Pain. In chronic primary pain syndromes (left), pain can be conceived as a disease, whereas in chronic
secondary pain syndromes (right), pain initially manifests itself as a symptom of another disease such as breast cancer, a work accident, diabetic neuropathy,
chronic caries, inflammatory bowel disease, or rheumatoid arthritis. Differential diagnosis between primary and secondary pain conditions may sometimes be
challenging (arrows), but in either case, the patient’s pain needs special care when it is moderate or severe. After spontaneous healing or successful management
of the underlying disease, chronic pain may sometimes continue and hence the chronic secondary pain diagnoses may remain and continue to guide treatment as
well as health care statistics.
January 2019·Volume 160 ·Number 1 www.painjournalonline.com 21
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3.2. Chronic secondary pain syndromes
Chronic secondary pain syndromes are linked to other diseases
as the underlying cause, for which pain may initially be regarded
as a symptom. The proposed new ICD-11 codes become
relevant as a codiagnosis, when this symptom requires specific
care for the patient. This marks the stage when the chronic pain
becomes a problem in its own right. In many cases, the chronic
pain may continue beyond successful treatment of the initial
cause; in such cases, the pain diagnosis will remain, even after
the diagnosis of the underlying disease is no longer relevant. We
expect that this new coding will facilitate treatment pathways for
patients with these painful conditions by recognizing the chronic
pain problem early in the course of the disease. This is also
important if the underlying disease is painful in only some of the
patients; disease diagnosis alone does not identify these patients
without the codiagnosis of chronic pain.
3.2.1. Chronic cancer-related pain
Chronic cancer-related pain is defined as pain caused by the
cancer itself (by the primary tumor or by metastases) or by its
treatment (surgery, chemotherapy, and radiotherapy).
4
Pain is
a frequent and debilitating accompaniment of cancer and its
Figure 2. Multiple parenting concept of WHO for ICD-11. In contrast to the strictly linear structure of all previous versions of ICD,ICD-11 allows for any given
disease (“child”) to belong to more than one section (“parent”). This is called “multiple parenting.” “Chronic painful chemotherapy-induced polyneuropathy” is
illustrated here as one example. ICD,International Classification of Diseases.
22 R.-D. Treede et al.·160 (2019) 19–27 PAIN
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treatment.
10
It becomes more and more apparent that chronic
pain syndromes are prevalent in long-term survivors of cancer,
and that these chronic secondary pain syndromes include
neuropathic and musculoskeletal pains.
16
Chronic pain caused
by the cancer or by chemotherapy or radiation therapy is coded in
this section. Pain that is caused by surgical cancer treatment is
coded in the section of chronic postsurgical pain.
3.2.2. Chronic postsurgical or posttraumatic pain
Whether or not pain persists past normal healing time
7
is
operationalized most naturally for chronic pain after surgery or other
trauma, where the initiating events and normal healing times are
known. To be consistent with the definition of the parent entity
“chronic pain,” the temporal criterion of 3 months is also used as
cutoff here, although aspects of chronicity may be detectable
earlier.
27
Diagnostic entities within this category are divided
according to the initiating event being either surgical or nonsurgical
trauma.
39
Chronic postsurgical pain is a prime candidate for
prevention programs to be combined with the usual preparation of
a patient for surgery. Chronic posttraumatic pain is a major problem
in rehabilitation and return-to-work programs. In both cases, pain
often is neuropathic in nature (on average 30% of cases with a range
from 6% to 54% and more).
19
In such cases, “chronic peripheral
neuropathic pain” may be given as a codiagnosis.
3.2.3. Chronic neuropathic pain
Neuropathic pain is defined as pain caused by a lesion or disease of
the somatosensory nervous system.
23,44
This pain is typically
perceived within the innervation territory that is somatotopically
represented within the lesioned nervous system structure (projected
pain). Neuropathic pain may be spontaneous or evoked by sensory
stimuli (hyperalgesia and allodynia). Chronic neuropathic pain is
divided into chronic peripheral or chronic central neuropathic pain.
38
Algorithms for grading the diagnostic certainty have been pub-
lished.
14,44
The diagnosis of neuropathic pain requires a history of
nervous system injury, for example, by a stroke, nerve trauma or
diabetic neuropathy, and a neuroanatomically plausible distribution
of the pain. Negative (loss of sensory function) or positive sensory
signs (pain and paresthesia) must be compatible with the innervation
territory of the lesioned nervous structure. For the identification of
definite neuropathic pain, it is necessary to additionally demonstrate
the lesion or disease involving the nervous system, for example, by
imaging, biopsy, or neurophysiological tests. Questionnaires may be
useful as screening tools to support the clinical hypothesis of
neuropathic pain but are not diagnostic.
1
3.2.4. Chronic secondary headache or orofacial pain
This section is largely cross-referenced to the headache classifi-
cation of the International Headache Society (IHS) that is
implemented in full in the chapter on neurology.
21
The IHS
classification differentiates between primary (idiopathic) head-
aches, secondary (symptomatic) headaches, and orofacial pains
including cranial neuralgias. Chronic headache and orofacial pain
are defined as headaches or orofacial pains that occur for more
than 2 hours per day on at least 50% of the days during at least 3
months. Only chronic secondary headaches and chronic orofacial
pains are included here
6
; chronic primary headaches are listed
under chronic primary pain syndromes. The subdivisions of chronic
orofacial pain are more elaborate than in the IHS classification,
thanks to contributions from the IASP SIG on orofacial pain, and
include chronic dental pains and temporomandibular disorders.
5
3.2.5. Chronic secondary visceral pain
Chronic secondary visceral pain is defined as persistent or
recurrent pain that originates from internal organs of the head/
neck region and the thoracic, abdominal, and pelvic cavities.
40
The pain is usually perceived in somatic tissues of the body wall
(skin, subcutis, and muscle) in areas that receive the same
sensory innervation as the internal organ at the origin of the
symptom (referred visceral pain).
17
Diagnostic entities within this
category are subdivided according to the major underlying
mechanisms, ie, mechanical factors (eg, traction and obstruc-
tion), vascular mechanisms (ischemia and thrombosis), or
persistent inflammation.
2
Pain due to cancer or metastasis in
internal organs is coded in the chapter chronic cancer-related
pain,
4
whereas pain due to functional or unexplained mecha-
nisms is listed under chronic primary pain.
30
3.2.6. Chronic secondary musculoskeletal pain
Chronic secondary musculoskeletal pain is defined as persistent or
recurrent pain that arises as part of a disease process directly
affecting bone(s), joint(s), muscle(s), or related soft tissue(s).
32
Pain
may be spontaneous or movement-induced. This category is limited
to nociceptive pain and does not include pain that may be perceived
in musculoskeletal tissues but does not arise therefrom, such as the
pain of compression neuropathy or somatic referred pain. Diagnostic
entities within this category are subdivided according to the major
underlying mechanisms, ie, persistent inflammation of infectious,
autoimmune or metabolic etiology (eg, rheumatoid arthritis), structural
changes affecting bones, joints, tendons, or muscles (eg, symptom-
atic osteoarthrosis), or chronic musculoskeletal pain secondary to
diseases of the motor nervous system (eg, spasticity after spinal cord
injury or rigidity in Parkinson disease). Well-described apparent
musculoskeletal conditions for which the causes are incompletely
understood, such as nonspecific back pain or chronic widespread
pain, are included in the section on chronic primary pain.
30
3.3. Severity and other extension codes in ICD-11
Optional specifiers (called “extension codes” in WHO terminology) are
available for all chronic pain diagnoses and allow for recording pain
severity, its temporal course, and evidence of psychological and
social factors. The severity of chronic pain is proposed to be
determined as a compound measure of pain intensity, and pain-
related distress and task interference. Pain intensity denotes the
strength of the subjective pain experience (“how much does it hurt?”).
Pain-related distress is the multifactorial unpleasant emotional
experience of a psychological (cognitive, behavioral, and emotional),
social, or spiritual nature because of the persistent or recurrent
experience of pain (“how distressed are you by the pain?”).
22
Pain-
related interference describes how much the pain interferes with daily
activities and participation (“how much does the pain interfere with
your life?”). Each of the severity determinants (intensity, pain-related
distress, and interference) is rated by the patient on a numerical rating
scale from 0 to 10 and then transformed into WHO severity stages of
“mild,” “moderate,” and “severe” (Box 1). Temporal characteristics
can be coded as continuous pain, episodic recurrent pain, and
continuous pain with pain attacks.
The presence of significant psychological and social factors can
also be documented with an extension code. Psychological factors
in this sense are cognitive (such as catastrophizing or worry and
rumination),
12,43
behavioral (such as avoidance or endurance),
20,47
and emotional (such as fear or anger).
37,46
Social factors referto the
impact of chronic pain on the relationship with others and vice
January 2019·Volume 160 ·Number 1 www.painjournalonline.com 23
Copyright Ó2018 by the International Association for the Study of Pain. Unauthorized reproduction of this article is prohibited.
versa.
9,24
This extension code should be used when psychological
and social factors are judged to contribute to the onset, the
maintenance or exacerbations of pain or are regarded as relevant
consequences of the pain. Assigning this extension code does not
require a judgement regarding causal priorities or etiological
contributions. Because all chronic pain is regarded as a multifac-
torial, biopsychosocial phenomenon, this extension code is avail-
able for all chronic pain diagnoses and is not limited to the chronic
primary pain syndromes.
ICD-11 will be coordinated within the WHO Family of International
Classifications that also includes the International Code of Func-
tioning (ICF) and the International Code of Health Interventions
(ICHI).
48
Each ICD-11 code will refer to the relevant section of ICF as
“functional properties” of the ICD code.
51
A harmonization of ICD
with ICF is particularly relevant for chronic pain conditions because
both systems address pain and pain-associated disability. The ICF
was developed by the International Society for Physical and
Rehabilitation Medicine (ISPRM) with the WHO. A draft of the
functioning properties for chronic pain on the basis of the ICF
domains was developed jointly by IASP and ISPRM.
31
4. Discussion
The classification system for chronic pain conditions submitted
by IASP to WHO is compatible with ICD principles and aims to
improve pain research, health policy decisions, and patient care.
The temporal cutoff of 3 months for defining chronic pain is
arbitrary, but it is consistent with temporal cutoffs of other chronic
conditions. This clearly operationalized and easily measurable
criterion will help to use uniform criteria in health care statistics,
clinical trials, publications, and medical textbooks. It has the
advantage that clinicians, at a reasonable point in time, will be
alerted to the possibility that pain may be the leading or sole
medical problem of a given patient. The question whether pain
can become chronic at an earlier stage (sometimes called
“subacute”) is a research question that can now be addressed by
contrasting patient histories with this definition.
In the field of headache, precise and operationalized criteria for
diagnosis (eg, a strict temporal criterion for migraine) have greatly
facilitated research in all areas ranging from basic to epidemiological
science, which in turn informed the refinement of diagnostic criteria at
Box 1. Specifiers or “extension codes” in ICD-11
Pain severity
Pain intensity may be assessed verbally or on a numerical or visual rating scale. For the severity coding, the patient should be asked to rate the average pain intensityfor the last
week on an 11-point numerical rating scale (NRS) (ranging from from 0 “no pain” to 10 “worst pain imaginable”) or a 100-mm visual analogue scale (VAS):
Pain-related distress may be assessed by asking the person to rate the pain-related distress they experienced in the last week (multifactorial unpleasant emotional experience
of a cognitive, behavioral, emotional, social, or spiritual nature due to the persistent or recurrent experience of paint) on an 11-point numerical rating scale or a VAS from “no
pain-related distress” to “extreme pain-related distress” (“distress thermometer”).
Pain-related interference last week as rated by the patient on an 11-point NRS (from 0 “no interference” to 10 “unable to carry on activities”) or VAS (0 mm “no interference” to
100 mm “unable to carry on activities”).
Overall severity combines the ratings of intensity, distress, and disability using a 3-digit code: Example: A patient with a moderate pain intensity, severe distress, and mild
disability will receive the code “231.” The severity code is optional.
Temporal characteristics of the pain
The temporal course of the pain can be coded as "continuous" (the pain is always present), "episodic recurrent" (there are recurrent pain attacks with pain-free intervals) and
"continuous with pain attacks" (there are recurrent pain attacks as exacerbations of underlying continuous pain).
Presence of psychosocial factors
This extension code permits coding problematic cognitive (eg, catastrophizing, excessive worry), emotional (eg, fear, anger), behavioral (eg, avoidance) and/or social factors (eg, work,
relationships) that accompany the chronic pain. The extension code is appropriate if there is positive evidence that psychosocial factors contribute to the cause, the maintenance and/or the
exacerbation of the pain and/or associated disability and/or when the chronic pain results in negative psychobehavioral consequences (eg, demoralisation, hopelessness, avoidance, withdrawal).
mild pain NRS: 1-3; VAS: ,31 mm
moderate pain NRS: 4-6; VAS: 31-54 mm
severe pain NRS: 7-10; VAS: 55-100 mm
mild distress NRS: 1-3; VAS: ,31 mm
moderate distress NRS: 4-6; VAS: 31-54 mm
severe distress NRS: 7-10; VAS: 55-100 mm
Code 0 no interference
Code 1 mild interference; NRS: 1-3; VAS: ,31 mm
Code 2 moderate interference; NRS: 4-6; VAS: 31-54 mm
Code 3 severe interference; NRS: 7-10; VAS: 55-100 mm
24 R.-D. Treede et al.·160 (2019) 19–27 PAIN
®
Copyright Ó2018 by the International Association for the Study of Pain. Unauthorized reproduction of this article is prohibited.
a later stage. One of the aims of the new classification of chronic pain
is to guide research on chronic pain onto the same path as research
on headache disorders by providing clearly operationalized criteria
that can be used for clinical trials (could start immediately) as well as
health statistics (according to WHO plan: starting in 2022). A group of
US authors of the ACTTION initiative has published a list of desirable
characteristics of an ideal diagnostic system.
13
The classification of
chronic pain in ICD-11 fulfills many of those:
4.1. Biological plausibility
The organizing principle of the chronic pain classification is the
same as that used throughout ICD: give first priority to pain
etiology (primary pain syndromes, cancer-related pain, and
postsurgical or posttraumatic pain), followed by underlying
pathophysiological mechanisms (neuropathic pain), and finally
body site or affected organ system (headache or orofacial pains,
visceral pain, and musculoskeletal pain).
4.2. Exhaustiveness
Chronic pain may be a symptom of an underlying chronic
condition, but it frequently outlasts the normal healing process
and often no other underlying disease can be identified. The
proposed classification of chronic pain distinguishes between
chronic primary pain syndromes (long-term conditions in their
own right) and chronic secondary pain syndromes (symptoms of
another nonpain problem). The morbidity and mortality linear-
ization of ICD-11 lists diagnoses only down to the 6-digit level.
We made a major effort to assure completeness at that level.
ICD-11 automatically adds a category “other” at each level to
catch any cases that might have been missed. Below the 6-digit
level, some pain diagnoses have not yet been linked to this
classification; for those, new codes can be generated in the
foundation layer of ICD-11 and can then be linked as “children”
to the appropriate parent code in the morbidity and mortality
linearization. This flexibility is one of the strengths of ICD-11 over
previous versions of ICD.
4.3. Uniqueness
The principle of “multiple parenting” allows the same diagnosis to
be referenced in more than one category. In this regard, ICD-11
transcends the discipline-specific structure of previous versions.
It allows different angles from which to approach a diagnosis: An
oncologist will be able to look up chronic neuropathic
chemotherapy-induced pain among the cancer-related pain
diagnoses, whereas a neurologist will be able to find exactly the
same diagnosis from the perspective of chronic neuropathic pain.
4.4. Reliability over time
If the chronic pain condition persists, clinicians should
continue to use a diagnosis of chronic secondary pain even
after the causing medical condition has been treated suc-
cessfully or remitted. After longer periods of obvious dissoci-
ation between the medical causes and chronic pain, and with
clear evidence for other factors determining the chronic pain
condition, a change of the chronic pain diagnosis (eg, to
chronic primary pain, or to another chronic secondary pain
diagnosis) should be considered (Fig. 1).
4.5. Inter-rater reliability
This has been assessed in the case-coding field testing by WHO
in 2017 to a certain extent,
49
but those were very few pain cases,
and hence, more field testing is needed to further validate the
classification.
4.6. Clinical usefulness and simplicity
A pilot field testing in 2016 on consecutive cases in 1 primary care
center and in pain clinics in 4 countries showed that coding was
much easier than in ICD-10 and was straightforward for 97% of
the patients. One of the participating clinics continues to use the
ICD-11 classification ever since.
3
Utility for primary care is
discussed in a companion article.
42
The new classification of chronic pain may help to reduce stigma
in many cultures.
25
The introduction of chronic primary pain as
a new diagnostic entity recognizes conditions that affect a broad
group of pain patients who are not adequately represented in
categories defined strictly according to either somatic or psycho-
logical etiology.
36
Because of the success of the behavioral
neurosciences, even mental disorders can nowadays no longer
be considered purely nonsomatic. Of note, all chronic pain, including
chronic primary pain, will be coded outside the realm of psychiatric
disorders. This accords more with the current scientific understand-
ing of chronic pain and often aligns better with patients’ own views.
All clinically relevant chronic pain is conceptualized within the
biopsychosocial model. The 7 major categories of chronic pain
represent a compromise between comprehensiveness and
practical applicability of the classification system. Several
clinically important conditions that were neglected or inade-
quately represented in previous ICD revisions are now included as
diagnoses, eg, chronic cancer-related pain, chronic postsurgical
pain, or chronic neuropathic pain. Etiological factors, temporal
factors, pain severity, and functional properties are reflected.
Assessment of pain intensity and severity should become part of
all routine medical examinations. Underlying causes and mech-
anisms should then be identified and lead to a personalized pain
management plan. Joint efforts by IASP and WHO have resulted
in the WHO analgesic ladder for treatment of cancer pain in 1986.
Now is the time for a similar coordinated effort to promote
improved diagnostic classification and multimodal management
approaches for all chronic pain around the world.
5. Conclusions
This is the first systematic classification of chronic pain that is also
apartoftheICD. We hope that this classification strengthens the
representation of chronic pain conditions in clinical practice and
research. The introduction of appropriate codes for chronic primary
and secondary pain syndromes is expected to promote research
on etiology and pathophysiology of these syndromes thanks to
clearly operationalized research diagnostic criteria. New entities
discovered by future research can be added to the foundation layer
of ICD-11 and will be anchored as “children” of the appropriate
“parent” codes of the classification presented here. This simple to
use classification is also expected to improve access to multimodal
care for all patients with chronic pain. It will facilitate accurate
epidemiological investigations and health policy decisions re-
garding chronic pain, including adequate financing of treatments.
Conflict of interest
R.-D. Treede reports grants from Boehringer Ingelheim, Astellas,
AbbVie, and Bayer, personal fees from Astellas, Gr ¨unenthal,
Bauerfeind, Hydra, and Bayer, and grants from EU, DFG, and
BMBF, outside the submitted work. W. Rief reports grants from
IASP, during the conduct of the study; personal fees from Heel;
January 2019·Volume 160 ·Number 1 www.painjournalonline.com 25
Copyright Ó2018 by the International Association for the Study of Pain. Unauthorized reproduction of this article is prohibited.
and personal fees from Berlin Chemie, outside the submitted
work. A. Barke reports personal fees from IASP, during the
conduct of the study. Q. Aziz reports grants and personal fees
from Grunenthal and personal fees from Allergan, outside the
submitted work. N.B. Finnerup has received honoraria for serving
on advisory boards or speaker panels from Teva, Novartis,
Astellas, Gr ¨unenthal, Mitshubishe Tanabe, Novartis, and Teva.
M. First reports personal fees from Lundbeck International
Neuroscience Foundation, outside the submitted work. M.A.
Giamberardino reports personal fees from IBSA Institute Bio-
chimique, personal fees from EPITECH Group, personal fees
from Helsinn Healthcare, grants from EPITECH Group, and
grants from Helsinn Healthcare, outside the submitted work. S.
Kaasa reports that he is Eir solution—stockholder. J. Scholz has
received research support from the Thompson Family Founda-
tion and Acetylon, and is now an employee of Biogen. This work
was completed before he joined the company. Biogen did not
have a role in the design, conduct, analysis, interpretation, or
funding of the research related to this work. S.A. Schug reports
that the Discipline of Anaesthesiology and Pain Medicine at the
University of Western Australia, but not S.A. Schug personally,
has received research and travel funding and speaking and
consulting honoraria from Andros Pharmaceuticals, Aspen,
bioCSL, Eli Lilly, Grunenthal, Invidior, Janssen, Luye Pharma,
Mundipharma, Pfizer, Pierre Fabre, Seqirus and iX Biopharma,
outside the submitted work. R. Benoliel, M.I. Bennett, M. Cohen,
S. Evers, B. Korwisi, E. Kosek, P. Lavand’homme, M. Nicholas
and S. Perrot, B.H. Smith, P. Svensson, and J.W.S. Vlaeyen have
nothing to disclose. Shuu-Jiun Wang reports personal fees from
Eli-Lilly, personal fees from Daiichi-Sankyo, grants and personal
fees from Pfizer, Taiwan, personal fees from Eisai, personal fees
from Bayer, and personal fees from Boehringer Ingelheim,
outside the submitted work.
Acknowledgements
The authors are members of the Classification of Pain Diseases
Task Force of the International Association for the Study of Pain
(IASP), an NGO in official relationship with WHO. The IASP gave
logistical and financial support to perform this work. Former IASP
presidents Eija Kalso and Fernando Cervero initiated this task
force. The authors are grateful for the unwavering support of Dr.
Robert Jakob and his team at WHO.
Appendix A. Supplemental digital content
Supplemental digital content associated with this article can be
found online at http://links.lww.com/PAIN/A658. SDC includes
a complete reference list of the diagnoses entered into the
foundation with the foundation IDs as well as the extension codes
(specifier). Since the complete list is contained, the material is
identical for all papers of the series.
Article history:
Received 19 June 2018
Accepted 30 July 2018
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January 2019·Volume 160 ·Number 1 www.painjournalonline.com 27
Copyright Ó2018 by the International Association for the Study of Pain. Unauthorized reproduction of this article is prohibited.
... Chronic pain continues to be recognized as a major health problem with varying impacts on quality of life and increases health costs, which mainly includes neuropathic pain (NP), inflammatory pain, and cancer pain (1,2). Chronic pain is projected to impact 37% of Americans by 2030, creating an additional economic burden of $635 billion (3,4). ...
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(1) Background: Endometriosis is a frequent chronic pain condition in women of fertile age. Pain management with analgesics is frequently used by women with endometriosis. During the COVID-19 pandemic, access to health services was temporarily restricted in various countries for persons without serious conditions, resulting in increased physical and mental health issues. The present study was conducted in order to assess the risk factors predicting increased analgesic intake by women with endometriosis during the COVID-19 pandemic. (2) Methods: The increased intake of over-the-counter (OTC) and prescription-only (PO) analgesics was assessed with an anonymous online questionnaire, along with demographic, pandemic-specific, disease-specific, and mental health characteristics. Anxiety and depression were assessed with the Generalized Anxiety Disorder Scale (GAD-2) and the Patient Health Questionnaire for Depression (PHQ-2), respectively. Pain-induced disability was assessed with the pain-induced disability index (PDI). (3) Results: A high educational level (OR 2.719; 95% CI 1.137-6.501; p = 0.025) and being at higher risk for depressive disorders, as measured by PHQ-2 ≥ 3 (OR 2.398; 95% CI 1.055-5.450; p = 0.037), were independent risk factors for an increased intake of OTC analgesics. Current global pain-induced disability (OR 1.030; 95% CI 1.007-1.054; p = 0.010) was identified as a risk factor for an increased intake of PO pain medication. The degree of reduction in social support and in social networks were independent predictors of an increased intake of PO analgesics in a univariate logistic regression analysis, but lost significance when adjusted for additional possible influencing factors. (4) Conclusions: In this population, an increased intake of OTC analgesics was related to a higher educational level and having a depressive disorder, while a higher pain-induced disability was an independent risk factor for an increased intake of PO analgesics. Pandemic-specific factors did not significantly and independently influence an increased intake of analgesics in women with endometriosis during the first wave of the COVID-19 pandemic in Germany. Healthcare providers should be aware of the possible factors related to increased analgesic use in women with endometriosis in order to identify persons at risk for the misuse of pain medication and to prevent potential adverse effects.
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Many experimental sleep deprivation (SD) studies were conducted to clarify the causal relationship between sleep and pain. This systematic review and meta-analysis aimed to update the evidence regarding the effects of different experimental SD paradigms on various pain outcomes. Five databases were searched from their inception to June 2022. Separate random-effects models were used to estimate the pooled effect sizes (ES) of different experimental SD paradigms on various pain outcomes. Thirty-one studies involving 699 healthy individuals and 47 patients with chronic pain were included. For healthy individuals, limited evidence substantiated that total SD significantly reduced pain threshold and tolerance (ES 0.74–0.95), while moderate evidence supported that partial SD significantly increased spontaneous pain intensity (ES 0.30). Very limited to moderate evidence showed that sleep fragmentation significantly increased peripheral and central sensitization in healthy individuals (ES 0.42–0.79). Further, there was very limited evidence that total or partial SD significantly aggravated spontaneous pain intensity in people with chronic pain. Our results accentuated that different SD paradigms differentially increased subjective pain intensity and worsened peripheral/central pain sensitization in healthy individuals, whereas the corresponding findings in people with chronic pain remain uncertain. Further rigorous studies are warranted to quantify their relationships in clinical populations.
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Background Burning mouth sensation is a common symptom with varying etiologies that can affect patient quality of life. The authors aimed to investigate the clinical characteristics, differentiate the underlying causes, and evaluate the impact on quality of life of patients with burning mouth sensation. Case Description A retrospective cohort study of 583 patients with burning mouth sensation symptoms was conducted. Demographic features, clinical characteristics, and associated systemic comorbidities of patients were collected. The 14-item Oral Health Impact Profile Questionnaire score and posttreatment follow-up were evaluated and analyzed among patients. In total, 583 patients with burning mouth sensation symptoms were enrolled; perimenopausal women were most affected; mean (SD) age was 57.04 (12.03) years, and the female to male ratio was 7:1. Patients were stratified into 178 patients (30.53%) with burning mouth syndrome (BMS) and 405 patients (69.47%) without BMS. No significant differences were found for age, sex, clinical characteristics, and 14-item Oral Health Impact Profile Questionnaire scores between BMS and no BMS groups. Notably, 72 of 119 patients without BMS who participated in follow-up had received referrals and treatment for systemic diseases, of which 76.39% achieved complete (45.83%) or partial (30.56%) remission. Among these patients, treatment for gastrointestinal disorders (92.59%), oral candidiasis (78.57%), thyroid diseases (66.67%), and avoidance of local irritants (62.50%) were most effective, and they were perpetuated as the common underlying causes. Practical Implications The study results implied significance of adopting multidisciplinary management of burning mouth sensation. It is imperative for dentists and physicians to strengthen their collaborative relationships and focus on both systemic and oral conditions in these patients.
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Background One of the obstacles in chronic pain management is the attitude of healthcare professionals. Although literature reports that the negative attitudes of healthcare professionals such as stigmatizing their patients with chronic pain and applying inadequate treatment cause failure in chronic pain management, there is no scale to measure the attitudes of healthcare professionals towards patients with chronic pain. Purpose This study aimed to develop a scale for identifying healthcare professionals’ attitudes towards patients with chronic pain. Method We prepared a draft scale in the form of five-point Likert. We applied the draft scale to 379 voluntary healthcare professionals working in two hospitals in 2019. Internal consistency and testretest methods were employed to determine the reliability of the scale. Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were used for construct validity. Findings According to the EFA, the scale had two factors explaining 45.68 of the total variant. We labelled the first factor “sensitivity orientation” and the second factor was labelled “misconception orientation”. Cronbach Alpha coefficients were 0.88 and 0.75 for the first and second factors respectively. Test-retest method reliability was r = 0.83 in the first factor and r = 0.75 in the second factor. The CFA showed that they were within the limits of acceptable fit values. Conclusions Our study found that the scale for healthcare professionals’ attitudes towards patients with chronic pain is a valid and reliable tool.Keywords: Healthcare professionals, chronic pain, attitude, scale development.
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This chapter will provide a broad overview of the prevalence of chronic pain in the worldwide population along with a brief historical context to the current terminology and framework of pain taxonomy. It will also highlight the process the International Association for the study of Pain underwent to align pain terms and diagnoses with the current version of the ICD-11. As you will learn the current pain taxonomy is a living framework to develop common terminology that could help direct clinical care, research, and education while aligning with the current iteration of the international classifications of diseases (ICD) codes.
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There are intriguing theories regarding the biology of fibromyalgia. Whilst several researchers assume it is a psychogenic, others believe that fibromyalgia is a disease of neurological sensitization (an overactive alarm system). Fibromyalgia is a clinical entity that present with a mix of the symptoms including chronic widespread pain and other non-pain linked symptoms, such as poor sleep, fatigue and cognitive disturbances. Furthermore, fibromyalgia exhibits substantial variation not only between various patients, but also in the same patient during the disease course. Identifying a common language and classification to diagnose and treat fibromyalgia represent another challenge, as patients may seek care from different disciplines (such as rheumatology, general practice, neurology, psychology, or psychiatry and in some cases orthopedic surgery) with unique perspectives and terminologies. Furthermore, in concordance with other medically unexplained pain syndromes, fibromyalgia may be classified in several ways (such as functional somatic syndrome, chronic widespread pain syndrome, persistent somatoform pain disorder, somatic symptom disorder, affective spectrum condition, and central sensitivity syndrome). This chapter will discuss the debate of fibromyalgia as a bitterly controversial condition, the science of pain and where fibromyalgia fits in. It will then discuss fibromyalgia as a pain processing problem, different sources of pain in fibromyalgia patients and the wind-up theory. The chapter will expand to discuss Fibromyalgia associated comorbidities, fibromyalgia pain in the clinical setting, fibromyalgianess, neuroimaging, as well as pain pathways and the pharmacotherapy of Fibromyalgia.
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Chronic and neuropathic pain are both difficult for patients to tolerate and for clinicians to treat effectively. It differs from other types of pain in etiology and impact, which in turn affects the duration and modalities of treatment options. Also, the challenge in management arises from the complex nature of pathophysiology, wide varieties of assessment tools and need for multidisciplinary approach for management.
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This article examines the occurrence of chronic pain across the human lifespan from pediatrics and adolescents through adulthood and concludes with geriatrics (>65). As a subset of the adolescent and adult age group, the article also explores the impact of chronic pain involving the obstetric population. Within the age groups and populations, we explore available information regarding prevalence, epidemiology, and impact of chronic pain surrounding each group as well as some of the common pain conditions and syndromes unique to a given group. While not focusing on treatment, the article reviews physiologic and other factors impacting treatment in a given group.
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The upcoming 11th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD) of the World Health Organization (WHO) offers a unique opportunity to improve the representation of painful disorders. For this purpose, the International Association for the Study of Pain (IASP) has convened an interdisciplinary task force of pain specialists. Here, we present the case for a reclassification of nervous system lesions or diseases associated with persistent or recurrent pain for ≥3 months. The new classification lists the most common conditions of peripheral neuropathic pain: trigeminal neuralgia, peripheral nerve injury, painful polyneuropathy, postherpetic neuralgia, and painful radiculopathy. Conditions of central neuropathic pain include pain caused by spinal cord or brain injury, poststroke pain, and pain associated with multiple sclerosis. Diseases not explicitly mentioned in the classification are captured in residual categories of ICD-11. Conditions of chronic neuropathic pain are either insufficiently defined or missing in the current version of the ICD, despite their prevalence and clinical importance. We provide the short definitions of diagnostic entities for which we submitted more detailed content models to the WHO. Definitions and content models were established in collaboration with the Classification Committee of the IASP's Neuropathic Pain Special Interest Group (NeuPSIG). Up to 10% of the general population experience neuropathic pain. The majority of these patients do not receive satisfactory relief with existing treatments. A precise classification of chronic neuropathic pain in ICD-11 is necessary to document this public health need and the therapeutic challenges related to chronic neuropathic pain.
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Chronic visceral pain is a frequent and disabling condition. Despite high prevalence and impact, chronic visceral pain is not represented in ICD-10 in a systematic manner. Chronic secondary visceral pain is chronic pain secondary to an underlying condition originating from internal organs of the head or neck region or of the thoracic, abdominal, or pelvic regions. It can be caused by persistent inflammation, by vascular mechanisms or by mechanical factors. The pain intensity is not necessarily fully correlated with the disease process, and the chronic visceral pain may persist beyond successful treatment of the underlying cause. This article describes how a new classification of chronic secondary visceral pain is intended to facilitate the diagnostic process and to enable the collection of accurate epidemiological data. Furthermore, it is hoped that the new classification will improve the tailoring of patient-centered pain treatment of chronic secondary visceral pain and stimulate research. Chronic secondary visceral pain should be distinguished from chronic primary visceral pain states that are considered diseases in their own right.
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This article describes chronic secondary headache and chronic orofacial pain (OFP) disorders with respect to the new International Classification of Diseases (ICD-11). The section refers extensively to the International Classification of Headache Disorders (ICHD-3) of the International Headache Society that is implemented in the chapter on Neurology in ICD-11. The ICHD-3 differentiates between primary (idiopathic) headache disorders, secondary (symptomatic) headache disorders, and OFP disorders including cranial neuralgias. Chronic headache or OFP is defined as headache or OFP that occurs on at least 50% of the days during at least 3 months and lasting at least 2 hours per day. Only chronic secondary headache and chronic secondary OFP disorders are included here; chronic primary headache or OFP disorders are listed under chronic primary pain syndromes that have been described in a companion publication. The subdivisions of chronic secondary OFP of ICHD-3 are complemented by the Diagnostic Criteria for Temporomandibular Disorders and contributions from the International Association for the Study of Pain Special Interest Group on Orofacial and Head Pain and include chronic dental pain. The ICD-11 codes described here are intended to be used in combination with codes for the underlying diseases, to identify patients who require specialized pain management. In addition, these codes shall enhance visibility of these disorders in morbidity statistics and motivate research into their mechanisms.
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The upcoming 11th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD) of the World Health Organization (WHO) offers a unique opportunity to improve the representation of painful disorders. For this purpose, the International Association for the Study of Pain (IASP) has convened an interdisciplinary task force of pain specialists. Here, we present the case for a reclassification of nervous system lesions or diseases associated with persistent or recurrent pain for $3 months. The new classification lists the most common conditions of peripheral neuropathic pain: trigeminal neuralgia, peripheral nerve injury, painful polyneuropathy, postherpetic neuralgia, and painful radiculopathy. Conditions of central neuropathic pain include pain caused by spinal cord or brain injury, poststroke pain, and pain associated with multiple sclerosis. Diseases not explicitly mentioned in the classification are captured in residual categories of ICD-11. Conditions of chronic neuropathic pain are either insufficiently defined or missing in the current version of the ICD, despite their prevalence and clinical importance. We provide the short definitions of diagnostic entities for which we submitted more detailed content models to the WHO. Definitions and content models were established in collaboration with the Classification Committee of the IASP's Neuropathic Pain Special Interest Group (NeuPSIG). Up to 10% of the general population experience neuropathic pain. The majority of these patients do not receive satisfactory relief with existing treatments. A precise classification of chronic neuropathic pain in ICD-11 is necessary to document this public health need and the therapeutic challenges related to chronic neuropathic pain.
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Worldwide, the prevalence of cancer is rising and so too is the number of patients who survive their cancer for many years thanks to the therapeutic successes of modern oncology. One of the most frequent and disabling symptoms of cancer is pain. In addition to the pain caused by the cancer, cancer treatment may also lead to chronic pain. Despite its importance, chronic cancer-related pain is not represented in the current International Classification of Diseases (ICD-10). This article describes the new classification of chronic cancer-related pain for ICD-11. Chronic cancer-related pain is defined as chronic pain caused by the primary cancer itself or metastases (chronic cancer pain) or its treatment (chronic postcancer treatment pain). It should be distinguished from pain caused by comorbid disease. Pain management regimens for terminally ill cancer patients have been elaborated by the World Health Organization and other international bodies. An important clinical challenge is the longer term pain management in cancer patients and cancer survivors, where chronic pain from cancer, its treatment, and unrelated causes may be concurrent. This article describes how a new classification of chronic cancer-related pain in ICD-11 is intended to help develop more individualized management plans for these patients and to stimulate research into these pain syndromes.
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Physical, mental, and social well-being are part of the concept of health according to the World Health Organization, in addition to the absence of disease and infirmity. Therefore, for a full description of a person's health status, the International Classification of Functioning, Disability and Health (ICF) was launched in 2001 to complement the existing International Classification of Diseases (ICD). The 11th version of the ICD (ICD-11) is based on so-called content models, which have 13 main parameters. One of them is functioning properties (FPs) that, according to the WHO, consist of the activities and participation components of the ICF. Recently, chronic pain codes were added to the 11th edition of the ICD, and hence, a specific set of FPs for chronic pain is required as a link to the ICF. In addition, pain is one of the 7 dimensions of the generic set of the ICF, which applies to any person. Thus, assessment and management of pain are also important for the implementation of the ICF in general. This article describes the current consensus proposal by the International Association for the Study of Pain (IASP) and the International Society of Physical and Rehabilitation Medicine (ISPRM) for a specific set of FPs of chronic pain, which will have to be empirically validated in a next step. The combined use of ICD-11 and ICF is expected to improve research reports on chronic pain by a more precise and adequate coding, as well as patient management through better diagnostic classification.
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The International Classification of Diseases, 11th Revision (ICD-11), proposes, for the first time, a coding system for chronic pain. This system contains 1 code for "chronic primary pain," where chronic pain is the disease, and 6 codes for chronic secondary pain syndromes, where pain developed in the context of another disease. This provides the opportunity for routine, standardised coding of chronic pain throughout all health care systems. In primary care, this will confer many important, novel advantages over current or absent coding systems. Chronic pain will be recognized as a centrally important condition in primary care. The capacity to measure incidence, prevalence, and impact will help in identification of human, financial, and educational needs required to address chronic pain in primary care. Finally, opportunities to match evidence-based treatment pathways to distinct chronic pain subtypes will be enhanced.
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Chronic musculoskeletal pain is defined as chronic pain arising from musculoskeletal structures such as bones or joints. Although comprising the most prevalent set of chronic pain conditions, it was not represented appropriately in the 10th edition of the International Classification of Diseases (ICD-10), which was organized mainly according to anatomical sites, was strongly focused on musculoskeletal disease or local damage, and did not consider the underlying mechanisms of pain. The new ICD-11 classification introduces the concept of chronic primary and secondary musculoskeletal pain, and integrates the biomedical axis with the psychological and social axes that comprise the complex experience of chronic musculoskeletal pain. Chronic primary musculoskeletal pain is a condition in its own right, not better accounted for by a specific classified disease. Chronic secondary musculoskeletal pain is a symptom that arises from an underlying disease classified elsewhere. Such secondary musculoskeletal pain originates in persistent nociception in musculoskeletal structures from local or systemic etiologies, or it may be related to deep somatic lesions. It can be caused by inflammation, by structural changes, or by biomechanical consequences of diseases of the nervous system. It is intended that this new classification will facilitate access to patient-centered multimodal pain management and promote research through more accurate epidemiological analyses.
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Chronic pain after tissue trauma is frequent and may have a lasting impact on the functioning and quality of life of the affected person. Despite this, chronic postsurgical and posttraumatic pain is underrecognised and, consequently, undertreated. It is not represented in the current International Classification of Diseases (ICD-10). This article describes the new classification of chronic postsurgical and posttraumatic pain for ICD-11. Chronic postsurgical or posttraumatic pain is defined as chronic pain that develops or increases in intensity after a surgical procedure or a tissue injury and persists beyond the healing process, ie, at least 3 months after the surgery or tissue trauma. In the classification, it is distinguished between tissue trauma arising from a controlled procedure in the delivery of health care (surgery) and forms of uncontrolled accidental damage (other traumas). In both sections, the most frequent conditions are included. This provides diagnostic codes for chronic pain conditions that persist after the initial tissue trauma has healed and that require specific treatment and management. It is expected that the representation of chronic postsurgical and posttraumatic pain in ICD-11 furthers identification, diagnosis, and treatment of these pain states. Even more importantly, it will make the diagnosis of chronic posttraumatic or postsurgical pain statistically visible and, it is hoped, stimulate research into these pain syndromes.
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This article describes a proposal for the new diagnosis of chronic primary pain (CPP) in ICD-11. Chronic primary pain is chosen when pain has persisted for more than 3 months and is associated with significant emotional distress and/or functional disability, and the pain is not better accounted for by another condition. As with all pain, the article assumes a biopsychosocial framework for understanding CPP, which means all subtypes of the diagnosis are considered to be multifactorial in nature, with biological, psychological, and social factors contributing to each. Unlike the perspectives found in DSM-5 and ICD-10, the diagnosis of CPP is considered to be appropriate independently of identified biological or psychological contributors, unless another diagnosis would better account for the presenting symptoms. Such other diagnoses are called "chronic secondary pain" where pain may at least initially be conceived as a symptom secondary to an underlying disease. The goal here is to create a classification that is useful in both primary care and specialized pain management settings for the development of individualized management plans, and to assist both clinicians and researchers by providing a more accurate description of each diagnostic category.