Unbearability of suffering at the end of life: the development of a new measuring device, the SOS-V.

Abstract

Unbearable suffering is an important issue in end-of-life decisions. However, there has been no systematic, prospective, patient-oriented research which has focused on unbearable suffering, nor is there a suitable measurement instrument. This article describes the methodological development of a quantitative instrument to measure the nature and intensity of unbearable suffering, practical aspects of its use in end-stage cancer patients in general practice, and studies content validity and psychometric properties.
Recognizing the conceptual difference between unbearability of suffering and extent or intensity of suffering, we developed an instrument. The compilation of aspects considered to be of importance was based on a literature search. Psychometric properties were determined on results of the first interviews with 64 end-stage cancer patients that participated in a longitudinal study in the Netherlands.
The instrument measures five domains: medical signs and symptoms, loss of function, personal aspects, aspects of environment, and nature and prognosis of the disease. Sixty nine aspects were investigated, and an overall score was asked. In 64 end-stage cancer patients the instrument was used in total 153 times with an average interview time varying from 20-40 minutes. Cronbachs alpha's of the subscales were in majority above 0.7. The sum scores of (sub)scales were correlated strongly to overall measures on suffering.
The SOS-V is an instrument for measuring the unbearability of suffering in end-stage cancer patients with good content validity and psychometric properties, which is feasible to be used in practice. This structured instrument makes it possible to identify and study unbearable suffering in a quantitative and patient-oriented way.

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BMC Palliative Care
Open Access
Research article
Unbearability of suffering at the end of life: the development of a
new measuring device, the SOS-V
Kees DM Ruijs*1, Bregje D Onwuteaka-Philipsen2, Gerrit van der Wal2 and
Ad JFM Kerkhof3
Address: 1Primary Care Center De Greev, Utrecht, the Netherlands, 2Department of Public and Occupational Health, EMGO Institute for Health
and Care Research, Expertise Center for Palliative Care, VU University Medical Center, Amsterdam, the Netherlands and 3Department of Clinical
Psychology, EMGO + Institute for Health and Care Research, VU University, Amsterdam, the Netherlands
Email: Kees DM Ruijs* - C.Ruys3@kpnplanet.nl; Bregje D Onwuteaka-Philipsen - b.philipsen@vumc.nl; Gerrit van
der Wal - g.vanderwal@vumc.nl; Ad JFM Kerkhof - ajfm.kerkhof@psy.vu.nl
* Corresponding author
Abstract
Background: Unbearable suffering is an important issue in end-of-life decisions. However, there
has been no systematic, prospective, patient-oriented research which has focused on unbearable
suffering, nor is there a suitable measurement instrument. This article describes the methodological
development of a quantitative instrument to measure the nature and intensity of unbearable
suffering, practical aspects of its use in end-stage cancer patients in general practice, and studies
content validity and psychometric properties.
Methods: Recognizing the conceptual difference between unbearability of suffering and extent or
intensity of suffering, we developed an instrument. The compilation of aspects considered to be of
importance was based on a literature search. Psychometric properties were determined on results
of the first interviews with 64 end-stage cancer patients that participated in a longitudinal study in
the Netherlands.
Results: The instrument measures five domains: medical signs and symptoms, loss of function,
personal aspects, aspects of environment, and nature and prognosis of the disease. Sixty nine
aspects were investigated, and an overall score was asked. In 64 end-stage cancer patients the
instrument was used in total 153 times with an average interview time varying from 20-40 minutes.
Cronbachs alpha's of the subscales were in majority above 0.7. The sum scores of (sub)scales were
correlated strongly to overall measures on suffering.
Conclusion: The SOS-V is an instrument for measuring the unbearability of suffering in end-stage
cancer patients with good content validity and psychometric properties, which is feasible to be used
in practice. This structured instrument makes it possible to identify and study unbearable suffering
in a quantitative and patient-oriented way.
Background
Suffering of patients is inseparably connected with the
work of the medical profession. Serious disease can result
in serious suffering. At some point, it is possible that
patients may consider their suffering unbearable. Some of
these patients may request euthanasia.
Published: 3 November 2009
BMC Palliative Care 2009, 8:16doi:10.1186/1472-684X-8-16
Received: 19 December 2008
Accepted: 3 November 2009
This article is available from: http://www.biomedcentral.com/1472-684X/8/16
© 2009 Ruijs et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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In the Netherlands, the discussion about euthanasia
started in the early seventies, and unbearable suffering
was the central theme [1]. In 2002, an act regulating
euthanasia, in which unbearable suffering is one of the
pivotal criteria for due care [2].
Since 1991, studies have been carried out in the Nether-
lands to achieve transparency in the frequencies of end-of-
life decisions [1-5]. Given an estimated number of 8.400
explicit requests for euthanasia each year, at a total of
about 140.000 deaths, patients consider their suffering
unbearable in the last phase of life in at least 6% of all
deaths [6]. The estimated frequency of euthanasia and
physician-assisted suicide was 1,8 percent of all deaths in
2005. The majority (87 percent) of these deaths took
place in primary care, and cancer was the most frequent
diagnosis (84 percent) [2,6]. However, all these studies
were physician-oriented.
The transparency about the nature and frequency of end-
of-life decisions in medical practice in the Netherlands is
not paralleled by a clear understanding of what patients
consider unbearable suffering, since in nearly four dec-
ades the nature of unbearable suffering has not yet been
studied through patient-oriented research [7]. Important
reasons for studying unbearable suffering this way are the
understanding of unbearable suffering, analysis of end-of-
life decisions, and assessing and directing care needed.
We planned a longitudinal, prospective, quantitative
patient-oriented study of the nature and intensity of
unbearable suffering in end-stage cancer patients in pri-
mary care. In 2001, in preparation of our study, we per-
formed a Medline literature search for patient-oriented
studies focusing on unbearable suffering. Key words we
used in different combinations were: unbearable suffer-
ing, suffering, quality of life, measure, cancer patients, pal-
liative, general practice, primary care, euthanasia. We also
studied a sample of convenience from the Dutch medical
literature concerning unbearable suffering and end-of-life
decisions. A compilation of over 200 articles related to the
subject was studied. No patient-oriented research investi-
gating unbearable suffering was found. Above that, no
measurement instrument for unbearable suffering was
found. At first glance, a quality-of-life instrument would
appear an option. However years of clinical, and research
experience within the research group showed a recurring
phenomenon: in patients in whom no difference in qual-
ity of life was observed or expressed some would consider
their suffering unbearable and ask for euthanasia, and
others would not. In other words, the extent to which bur-
densome signs or symptoms are present does not neces-
sarily parallel the experience of unbearability. This is what
distinguishes unbearable suffering from health-related
quality of life which is usually measured by assessing the
extent to which signs or symptoms are present.
We decided to develop an instrument to measure the
unbearability of suffering at the end of life. This article
describes its development, giving insight in the content
validity of the measurement instrument. Furthermore, we
describe our experience with the practical use of the
instrument in end-stage cancer patients and the psycho-
metric properties of the instrument.
Methods
For the systematic development of the instrument we
defined unbearable suffering, decided whether or not
non-disease-related aspects should be included, defined
an integral framework of the main domains of suffering,
implemented specific aspects of suffering in the frame-
work, and developed a method of questioning patients
about (un)bearability. The research group provided exper-
tise in medicine (especially general practice and public
health), psychology and health sciences.
Definition
We defined unbearable suffering as a subjective experi-
ence of suffering that is so serious and uncontrollable that
it overwhelms ones bearing capacity. This experience is
not a steady state, but a state that fluctuates in intensity.
This corresponds with the experience of physicians, who
observe how a patient can feel unwell one day, and then
better on another day. This can for instance depend on
activities during the day, social contacts or treatment, or
can have no apparent explanation.
Framework of suffering and process of selection of aspects
The experience of suffering is a multidimensional entity
with physical, psychological, social, existential and spirit-
ual dimensions [8-10]. Thus, in the medical professional
field, suffering will comprise disease-related and non-dis-
ease-related aspects and an integral instrument should
account for both, resulting in a comprehensive measure-
ment of suffering. A second reason to include non-dis-
ease-related aspects is the relationship
unbearable suffering and end-of-life decisions, which in
it's essence are existential decisions [11]. In the literature
we found two frameworks for the experience of suffering
[12,13] with focus upon the domains of suffering as
encountered in medical practice. We selected a framework
with five domains: (I) medical signs and symptoms, (II)
loss of function, (III) personal aspects, (IV) aspects of
environment, (V) nature and prognosis of the disease
[12]. Therefore, we named the instrument the State Of
Suffering-Five (for five domains), in short: SOS-V 9 Addi-
tional file 1).
between
A compilation was made of aspects of suffering that were
considered to be of importance in the studied literature,
when focusing on end-stage cancer patients [1,4,7-
9,11,14-33]. In a process of reflection and interaction the
research group selected aspects and divided them over the

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five specific domains. Since this study originated in med-
ical practice, emphasis was laid on the domain of medical
signs and symptoms.
The items listed can predominantly be considered as
causal indicators, which may cause unbearable suffering if
present, while it is not necessary that people who suffer
unbearably score high on these items. Therefore, in devel-
oping a valid instrument an important aim is that the list
of items is comprehensive. This as opposed to selecting as
few items as possible to validly measure a concept, as is
done in items that can be considered effect indicators (e.g.
depression screening scales) [34,35]. Focussing on com-
prehensiveness, we selected 69 aspects, while working
towards an interview time of 30-45 minutes. Since a study
among terminally ill cancer patients showed that for a
majority of patients an interview with median duration of
83 minutes was acceptable [36], this could even leave time
to address other topics in the interview.
Measuring unbearable suffering
The next step was to formulate a question with which to
measure unbearable suffering per aspect. Quality of life
studies generally measure the extent or intensity of a
symptom or complaint. This is important information,
but as such it does not determine the unbearability of the
suffering. A high score for an aspect of suffering might be
unbearable for one person, but bearable for another per-
son. Therefore, we concluded that two questions would be
necessary: first asking about the intensity or extent to
which an aspect was present, followed by a question on
how unbearable it was.
Eligibility criteria and other interview- and study
information
Because of the target population of end-stage cancer
patients, the mode of gathering information was chosen
to be an interview. The patients were handed a card with
the answering options to help choosing their answer. For
this study, with the purpose of recording change in the last
phase of life, the recall period of the instrument was 'the
last two days'.
The interview was tested four times in patients with end-
stage cancer who only had a few months to live, after
which a few questions were reformulated. The resulting
instrument was used in the actual study which was carried
out in primary care in Utrecht, one of the four largest cities
in the Netherlands. The study was approved by the ethical
committee of VU University Medical Center. Patients were
eligible if they had incurable cancer, an estimated life-
expectancy of six months or less, were competent, had
adequate command of the Dutch language, were expected
to stay mostly at home, and had a general practitioner as
the primary responsible physician. Sixty four patients
were followed from inclusion until they deceased.
Forty five general practitioners invited eligible patients to
participate in the study. The interviews took place in the
patients home every two months, or sooner if the condi-
tion of the patient deteriorated (information provided by
the general practitioner). In this paper, the data on the
first interviews were used. In the first interview we used
the SOS-V and several other instruments, among which
the EORTC QLQ C30 [14], a health-related quality of life
measurement for cancer patients. If, during the interview,
the interviewer sensed that the general condition of the
patient was too poor, the interview was cut short. Then
preference was given to the SOS-V. The interview time was
estimated approximately. At the end, the patient was
asked how he or she had experienced the interview., This
was not rated as a score, but was asked more openly, in
order to end the interview on a more informal note.
Translation of the instrument
The original language of the study was Dutch. Therefore,
the validation of the instrument concerns the Dutch ver-
sion. For the purpose of international publications, a back
and forward translation into English took place. The
instrument was translated to English by a native speaker,
after which it was translated back into Dutch by a
researcher not involved in this study. The few differences
found were discussed between the two translators and one
of the researchers (BOP) to decide on the appropriate Eng-
lish translation.
Analysis of psychometric properties
Internal consistency was analysed with cronbachs alpha's
for the 5 domains and for the total of aspects. This was
done separately for the questions on the presence of the
aspect and for the questions on the unbearabilty of these
aspects. To examine the extent to which the conceptual
difference between (a) the presence of aspects, and (b) the
extent to which they lead to unbearable suffering actually
exists in practice, scatter plots of presence (a) versus the
sum cores of unbearability (b) were made for the sums
cores per domain. Furthermore, the correlations between
sum scores of the 5 domains and overall measures on
extent of, unbearability of and hopelessness of suffering
were calculated. Finally, the correlation between the sum
scores of the sub domains and sum scores of the total
SOS-V, and the sum score of the EORTC QLQ C-30 was
calculated.
Results
The SOS-V
Table 1 shows the SOS-V, with the five domains of experi-
ence of suffering which we distinguished, the division of
69 aspects of suffering over these domains, and the addi-
tional questions. The domain "medical signs and symp-
toms" consists of most aspects: 37 aspects ordered
following organ and functional systems.

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Table 2 shows the two questions we used per aspect to
measure the presence of the aspect, and the extent to
which it was unbearable. Since unbearable suffering was
defined as a condition that is present to a certain degree,
it was possible to measure it in a range of scores. We con-
structed a five point scale with a parallel description for
scoring. To keep the scoring simple we chose a uniform
scale for both questions. This had consequences for the
way in which the questions were formulated. The second
question was not asked if the first score was 1. If a patient
scored 4 or 5 for unbearability on an aspect, then in an
open-ended question the patient was asked to specify the
experience. To ensure comprehensiveness, after posing
questions on the 69 aspects, the patient was asked to
name any aspects of suffering that had not been men-
tioned. After that, there were three questions on the over-
all severity, unbearability, and hopelessness of the
respondents' suffering. To analyse dimensions which
determine the capacity to bear suffering the interview was
ended with four open questions addressing the nature of
one's capacity to bear suffering, the role of spirituality, the
influence of previous experience of suffering caused by
disease and unexpected positive consequences of one's
disease. The complete instrument can be seen in the
appendix.
Table 1: Domains and aspects of the SOS-V
Domains Aspects
I. Medical signs and symptoms General: 1: General discomfort (feeling miserable, feeling unwell) 2: Tired 3: Weakened 4: Not sleeping
well 5: Pain 6: Loss of appetite 7: Thirst
8: Smelling unpleasant 9: Changed appearance
Psychological: 10: Impaired clarity of thought 11: Loss of concentration 12: Memory loss 13: Feeling
tense 14: Feeling depressed 15: Feeling anxious.
Respiratory tract: 16: Shortness of breath 17: Coughing
Gastrointestinal tract and urinary tract: 18: Swallowing and oesophageal passage obstructed for
food 19: Swallowing and oesophageal passage obstructed for fluids 20: Nausea 21: Vomiting 22:
Constipation
23: Diarrhoea 24: Intestinal cramps 25: Incontinence of urine
26: Incontinence of faeces 27: Hiccups
Skin: 28: Pressure ulcers 29: Itch 30: Skin metastasis
Nervous and loco-motor system: 31: Paralyzed limbs 32: Impaired
co-ordination of movements 33: Incomprehensible speech 34: Impaired comprehension of speech 35:
Dizziness 36: Impaired sight 37: Impaired hearing
II. Loss of function
38: Impaired working capacity 39: Impaired performance of routine daily activities 40: Impaired leisure
activities 41: Help needed with housekeeping (shopping, cleaning the house) 42: Help needed with self-
care (washing, dressing, eating, visit to the bathroom) 43: Bedridden 44: Restricted sexuality
III. Personal aspectsSelf-appraisal: 45: Not satisfied with your own self (with who you are as a person) 46: Lived a life with
little purpose 47: Experienced little success in life 48: Experienced little happiness with family, partner for
life and/or friends 49: Trouble accepting present situation 50: Negative thoughts or worrying 51: Feelings
of guilt 52: Feelings of worthlessness 53: Feelings of loneliness 54: Feelings of hopelessness 55: Feelings of
not any longer being the same person 56: Feeling tired of life
Experience of loss of independence: 57:Feeling dependant on others
58: Feeling loss of control over your own life 59: Feeling of being a nuisance to others
Experience of future perspective: 60: Feeling of no longer being of importance to others in the
remaining time 61: Feeling no longer able to do the things you consider important in the remaining time
IV. Aspects of social environmentRelationship with family and friends: 62:Feeling insufficiently supported by family, friends and those
nearby 63: Feeling lonely because the most important people in your life are not there for you 64:
Feelings of shame 65: Experiencing that those who are near by consider your suffering too severe
Communication: 66: Unsatisfactory contact with family, friends and those who are near by
Aspects of care: 67: Insufficient availability of care.
V. Nature and prognosis of disease
68: Fear of future suffering 69: Fear of not any longer having the strength to bear the suffering
Missing aspects
70: Mention any aspects missing, and score correspondingly
Total score
71: How severe is your suffering overall? 72: How unbearable is your suffering overall? 73: How hopeless
is your suffering overall?
Additional questions
Four open ended questions (see appendix: the complete instrument)

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Practical use of the instrument
Our data collection started May 2003, and the inclusion
period lasted until April 2006. In the study group of 64
patients 175 interviews were held, 130 (76%) of which
were complete. Four times the interview was impossible,
because of the poor condition of the patient. The remain-
ing 45 interviews were incomplete in the sense that not all
the different sub-instruments had been administered; in
22 of these interviews the SOS-V was not completed. Thus
the SOS-V was completed in 153 interviews (85%). Two
interviews were interrupted because the patient was too
tired; on these occasions the interview was completed a
few days later. Completing the interview took approxi-
mately 60-75 minutes. In general, the completion of the
SOS-V took 20-40 minutes. When it took longer, this was
generally because the patients appreciated the opportu-
nity to talk about things that they felt were important.
They were given enough time to do so. As the experience
of the interviewers increased, the interview time tended to
decrease. In general, the interviews were experienced pos-
itively by the patients.
Eleven patients (17%) named 20 aspects in response to
the question to name aspects of their suffering that were
not among the 69 aspects. The analysis showed that seven
aspects, that were all mentioned once, were really addi-
tional: cramps in the extremities, oedema of feet, tingling
of feet after chemotherapy, poly urea, cold extremities,
irritation and intolerance due to loss of naivety, and the
legal bureaucracy involved in obtaining income when
sick. The other thirteen aspects mentioned, were attribut-
able to existing aspects of the SOS-V.
Psychometric properties
Table 3 shows the average scores on presence and unbear-
ability of the individual aspects for the first interviews.
Most frequently the averages are between 1 and 2. This is
related to the frequency an aspect is not present (and thus
also not unbearable). Of the aspects 47 of 69 aspects is
present in less than 50% of respondents. Table 4 shows
that the cronbach's alpha for the subscales varied between
0.57 and 0.89, and that most subscales had a cronbach's
alpha of over 0.7. This level can be seen as a level of suffi-
cient internal consistency[37]. The internal consistency of
the total SOS-V was substantial with cronbachs alpaha's of
0.90 for presence of aspects and 0.93 for unbearability of
aspects. Furthermore, for all (sub)scales the cronbach's
alpha's were higher for the questions on unbearability of
aspects than for the questions on presence of aspects.
Figure 1 shows that for all (sub)scales the answers for
presence were not identical to the answers for unbearabil-
ity. However, they were strongly correlated, with correla-
tions from 0,77 (for domain II) to 0.91 (for domain IV).
For all (sub)scales, in the majority of cases the sum score
for presence was higher than the sum score for unbeara-
bility.
Table 5 shows the correlations of sum scores of
(sub)scales with the three overall questions on suffering.
All but two correlations (between aspects of social envi-
ronment and overall unbearability of suffering, and
between nature and prognosis of disease and overall
hopelessness of suffering) between subscales and overall
measures were significant. In general, the (sub) scales'
questions on extent of suffering were somewhat higher
correlated to the overall extent of suffering than the over-
all unbearability of suffering; e.g. 0.72 versus 0.66 for the
total scale. Similarly, the (sub) scales' questions on
unbearability of suffering were somewhat higher corre-
lated with the overall unbearability than with the overall
extent of suffering. Domain II and IV were less correlated
to the overall measures of suffering, compared to the
other domains and the total SOS-V. The correlations of
the (sub)scales with overall measure of hopelessness of
suffering were generally somewhat lower than with the
other two overall measures. An exception was domain IV
for which the correlations were highest with overall hope-
lessness of suffering.
While the correlations between the total SOS-V scores and
the EORTC QLQ C30 were high (0.66 for aspect present
and 0.58 for aspect unbearable), the correlations differed
substantially per sub domain of the SOS-V: they were rel-
atively high for the first and second domain and lower for
the other domains, especially for domain IV. (Table 5)
Table 2: Questions about the unbearable suffering
For every aspect of the SOS-V the following two questions were asked:
1 Do you feel .......(aspect)? Is there ....... (aspect)?
If the answer on question 1 indicated that the aspect was present (= all answers other than 'not at all') question 2 was posed:
How unbearable was this?
If the answer on question 2 was 'seriously' or 'very seriously' more information on this was asked in an open-ended question.
2
Scale for question 1 and 2:
not at all - slightly - moderately - seriously - very seriously (could hardly be worse)
1 - 2 - 3 - 4 - 5

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Table 3: Average scores for presence (a) and unbearability (b) of the individual SOS-V aspect in the first interviews (n = 64)*
Aspecta.
b.
Aspecta.
b.
Domain I
1 General discomfort
2 Tired
3 Weakened
4 Not sleeping well
5 Pain
6 Loss of appetite
7 Thirst
9 Smelling unpleasant
10 Impaired mental clarity
11 Concentration loss
12 Memory loss
13 Feeling tense
14 Feeling depressed
15 Feeling anxious
16 Shortness of breath
17 Coughing
18 Swallowing [..] food
19 Swallowing [..] fluid
20 Nausea
21 Vomiting
22 Constipation
23 Diarrhoea
24 Intestinal cramps
25 Incontinence of urine
26 Incontinence of faeces
27 Hiccups
28 Pressure ulcers
29 Itch
30 Skin metastasis
31 Paralyzed limbs
32 Impaired coordination
33 Incomprehensible speech
34 Impaired comprehension speech
35 Dizziness
36 Impaired sight
37 Impaired hearing
Domain II
38 Impaired working capacity
39 Impaired in daily activities
40 Impaired leisure activities
41 Needing help housekeeping
42 Needing help self-care
43 Bedridden
44 Restricted sexuality
Domain III
45 Not satisfied with own self
46 Lived life with little purpose
47 Little success in life
48 Little happiness with family
49 Trouble accepting situation
50 Negative thoughts or worrying
51 Feelings of guilt
52 Feelings of worthlessness
53 Feelings of loneliness
54 Feelings of hopelessness
55 Feeling no longer same person
56 Feeling tired of life
57 Feeling dependent of others
58 Feeling loss of control life
59 Feeling being a nuisance
60 Feeling not important to others
61 Doing Important things not possible
Domain IV
62 Not supported sufficiently
63 Lonely/people not there for you
64 Feelings of shame
65 Close ones consider suffering severe
66 Unsatisfactory contact close ones
67 Insufficient availability of care
Domain V
68 Fear of future suffering
69 No longer having strength to suffer
2.4
3.2
3.1
1.9
2.3
2.3
2.1
1.6
1.9
2.1
2.0
1.9
1.5
1.4
2.1
1.5
1.6
1.3
1.5
1.4
1.6
1.2
1.4
1.3
1.1
1.3
1.1
1.4
1.1
1.1
2.0
1.6
1.1
1.5
1.7
1.8
2.4
2.7
2.9
1.8
2.2
2.0
1.5
1.5
1.9
1.9
1.7
1.7
1.4
1.3
2.7
1.3
1.6
1.4
1.6
1.6
1.5
1.2
1.4
1.3
1.1
1.4
1.1
1.3
1.0
1.1
2.0
1.7
1.1
1.5
1.6
1.7
1.7
3.2
3.2
3.4
1.9
2.1
2.0
1.6
3.2
2.8
2.7
1.6
2.0
1.5
1.3
1.3
1.2
1.4
2.2
1.7
1.2
1.4
1.5
1.5
1.5
1.2
2.8
1.6
1.7
1.3
2.6
1.2
1.1
1.2
1.4
2.3
1.7
1.2
1.4
1.3
1.5
1.4
1.3
2.6
1.7
1.7
1.3
2.6
1.1
1.4
1.1
1.6
1.2
1.4
1.1
1.4
1.1
1.6
1.2
1.4
1.9
1.8
2.0
1.8
* Average of score between 1 (not at all) and 5 (very seriously); if an aspect was not at all present (a), it was scored also as not at all unbearable (b).
Missing observations between 6 and 9
Table 4: Internal consistency of the SOS-V subscale and total used at the first interviews with patients in general practice with
incurable cancer with a life-expectancy of 6 months or less (cronbach's α, n = 64)*
(sub)scaleNumber of itemsa. Aspect present? b. Suffering Unbearable?
Domain I: Signs and symptoms
Domain II: Loss of functions
Domain III: Personal aspects
Domain IV: Aspects of social environment
Domain V: Nature and prognosis of disease
370.79
0.70
0.82
0.57
0.64
0.87
0.72
0.89
0.62
0.72
7
17
6
2
Total SOS-V690.900.93
* between 6 and 8 missing observations per (sub)scale

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Scatter plots of the sum scores on 'aspect present?' (x-axis) versus 'aspect unbearable?' (y-axis) for sub scales and total of the SOS-V
Figure 1
Scatter plots of the sum scores on 'aspect present?' (x-axis) versus 'aspect unbearable?' (y-axis) for sub scales
and total of the SOS-V.
100,0090,00 80,0070,0060,0050,00 40,00
100,00
90,00
80,00
70,00
60,00
50,00
40,00
Sum scores domain I
30,0025,0020,0015,0010,005,00
30,00
25,00
20,00
15,00
10,00
5,00
Sum scores domain II
50,0040,0030,0020,00
50,00
40,00
30,00
20,00
Sum scores domain III
20,0018,0016,0014,0012,0010,008,006,00
20,00
15,00
10,00
5,00
Sum scores domain IV
10,008,006,004,00 2,00
10,00
8,00
6,00
4,00
2,00
Sum scores domain V
250,00200,00 150,00100,00
250,00
200,00
150,00
100,00
Sum scores SOS-V total

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Discussion
Unbearable suffering may be feared or experienced by
patients with an incurable disease, but it has not yet been
the focus of patient-oriented studies. We carried out a pro-
spective, patient-oriented study to investigate the nature
and intensity of unbearable suffering, for which it was
necessary to develop a measurement instrument. Based
on a systematic study of the literature, we developed a
quantitative measurement instrument. We hypothesize
that unbearable suffering occurs when the suffering
exceeds the bearing capacity of the individual. For some
persons this may occur at the level of individual dimen-
sions. For other persons unbearable suffering may occur
when the sum of suffering of diverse dimensions exceeds
the bearing capacity. The approach of a framework of suf-
fering based on diverse domains may define a comple-
mentary pathway of palliative care, in which relieving
measures of care in one domain may result in increased
bearing capacity 'available' to bear suffering in another
domain. This mechanism may also account for aspects of
suffering within one domain.
Content validity refers to the extent to which the concepts
of interest are comprehensively represented by the items
of an instrument. Important in judging the content valid-
ity is whether the measurement aim, target population,
and underlying concepts are taken into consideration
appropriately in developing the instrument [37]. The
above shows that this has been done in developing the
SOS-V. Furthermore, in selecting items for the SOS-V we
used literature, expert opinions and the target population.
Although the pilot study was limited to a few patients of
the target population, the use of the instrument in the
study showed that most patients did not add extra items.
This suggests that among the target population the item
list is generally comprehensive. This opportunity to add
relevant items is important, as suffering is a subjective
experience. It is especially important when the instrument
is used in other populations than the population for
which it was developed. For instance, in the Netherlands,
virtually all people have health insurance. Therefore, the
financial impact of a life-limiting illness might be a more
important aspect in countries with lower coverage of
health insurance. Similarly, it is possible that in a secular-
ized country like the Netherlands spiritual issues are dif-
ferent than in other countries.
The comparison with the overall scores on suffering sug-
gests that the SOS-V actually measures suffering. The
added value of the use of the SOS-V compared to overall
Table 5: Correlations between sum scores of SOS-V (sub)scales with patient with patient's general feeling of suffering and sum score of
the QLQ C-30; first interviews with patients in general practice with incurable cancer with a life-expectancy of 6 months or less
(Spearman R, n = 64)*
Overall Questions on suffering of the SOS-V
Extent of suffering Unbearability of suffering
QLQ C-30
Sum ScoreHopelessness of suffering
SOS-V
(sub)scale
a. Aspect
present?
b.
Suffering
Unbearable
?
a. Aspect
present?
b.
Suffering
Unbearable
?
a. Aspect
present?
b.
Suffering
Unbearable
?
a.
Aspect
present?
b.
Suffering
Unbearable
?
Domain I:
Signs and
symptoms
Domain II:
Loss of
functions
Domain III:
Personal
aspects
Domain IV:
Aspects of
social
environment
Domain V:
Nature and
prognosis of
disease
0.71‡
0.70‡
0.51‡
0.42‡
0.64‡
0.74‡
0.71‡
0.61‡
0.33†
0.43‡
0.34†
0.41‡
0.28†
0.52‡
0.64‡
0.54‡
0.64‡
0.62‡
0.53‡
0.58‡
0.64‡
0.70‡
0.36‡
0.38†
0.35‡
0.30†
0.46‡
0.43‡
0.29†
0.240.170.15
0.56‡
0.57‡
0.33†
0.27 0.70‡
0.73‡
0.230.30†
Total SOS-V 0.72‡
0.69‡
0.61‡
0.55‡
0.66‡
0.75‡
0.66‡
0.58‡
* between 8 and 15 missing observations per correlation
† significant p-value< 0.05
‡ significant p-value< 0.01

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scores is that it gives insight in the sources of suffering. The
internal consistency of the instrument is acceptable,
except may be for domain IV and V. However, it is debat-
able how necessary internal consistency is in an instru-
ment of which the items are mainly causal indicators
[35,36]. A limitation of the study is that it was not feasible
to study test-retest reliability. In studies in patients in the
last phase of life the retest should take place within less
than a week of the first interview [37], and we assessed
that this would limit the willingness to participate in the
prospective part of the study with interviews every 2
months (a period too long for test-retest).
In the development of the instrument, the conceptual dif-
ference between the presence of an aspect and it's unbear-
ability was an important starting point. The results show
that there is indeed a difference between presence of
aspects and unbearability. However, the difference is not
as large as we expected. In interpreting the correlations
between presence and unbearability, it should be under-
stood that if an aspect was not present, by definition
unbearability was also not present. This contributed to the
high correlations, especially when many aspects were not
present. In light of the conceptual difference between
presence and unbearability, and the differences found
between these (however small), we think it is important
that the SOS-V consists of both questions. However, it
could be debated that depending on the purpose of use of
the SOS-V, and the need for briefness in the data collec-
tion one could opt for only one of the questions (either on
presence or on unbearability).
The relatively high correlations of the SOS-V scores with
the total score on the EORTC QLQ C30 are an indication
for criterion validity of the instrument. At the same time,
the fact that this high correlation is especially to be con-
tributed to the first two domains -- 'medical signs and
symptoms' and 'loss of function' -- confirms the difference
between health-related quality of life and suffering. The
SOS-V gives more information on the less medical, more
psychosocial aspects of suffering. That this is relevant is
indicated by the significant correlations between the sub
domains III to V and the overall measures of suffering.
In our study of 64 end-stage cancer patients, 175 inter-
views were carried out. The SOS-V was completed 153
times, which demonstrates the feasibility of the instru-
ment in practice. The interview time for the SOS-V varied
between 20-40 minutes; the duration of the interviews
was influenced by open-ended questions asking for more
specific information if the scores were high, and also by
the way in which the patients appreciated the opportunity
to talk about their disease and its impact on their lives. For
some patients the interview time was too long. After com-
pletion of other parts of the interview 22 times patients
were too tired for the SOS-V, and four times the interview
was impossible because of the poor condition of the
patient.
Conclusion
We conclude that with the development of the SOS-V we
developed an instrument for measuring the unbearability
of suffering in end-stage cancer patients with a good con-
tent validity and psychometric properties, which is feasi-
ble to be used in practice. This quantitative instrument to
measure the unbearability of suffering offers an important
step to better understanding the phenomenon of unbear-
able suffering through gaining information directly from
patients. It also will make it possible to study whether pal-
liative care interventions influence the experienced
unbearability of suffering. Of course, when used in other
countries, in other languages, or in other patient groups,
attention for validation of the instrument is again impor-
tant.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
All authors contributed to the design of the study and the
development of the SOS-V. BOP is responsible for acqui-
sition of funding. KR participated in data collection and
drafted the manuscript. AK, GvdW, BOP have been in
revising the manuscript for important intellectual con-
tent. All authors read and approved of the final manu-
script.
Additional material
Acknowledgements
We would like to thank Janneke Goedhart for organizing the data collection
and interviewing the patients. This study was funded by an Aspasia fund
from the Netherlands Organisation for Scientific Research (NWO).
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Additional file 1
SOS-V. the complete SOS-V measuring instrument.
Click here for file
[http://www.biomedcentral.com/content/supplementary/1472-
684X-8-16-S1.pdf]

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