Flank pain has a significant adverse impact on quality of life in ADPKD: the CYSTic-QoL study

Abstract

Background
Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disorder and a major cause of kidney failure worldwide. However, its impact on quality-of-life has not been systematically explored.

Methods
The CYSTic-QoL study was an observational study designed to study quality-of-life in adult European ADPKD patients with an eGFR ≥30 ml/min/1.73m2. 465 patients were recruited from six expert European centres with baseline data recorded including HR-QoL (Health-Related Quality of Life) incorporating a Kidney Disease QoL short form questionnaire (KDQoL-SF v1.3), magnetic resonance imaging (MRI) for Total Kidney Volume (TKV) measurements and DNA for genotyping.
The cohort was stratified by baseline eGFR, TKV or genotype and correlated with HR-QoL scores. Bivariate and multivariate analyses were applied to examine the relationship between HRQoL and variables of interest. KDQoL-SF scores were calculated using an online tool provided by the RAND organisation. For SF36 (short form-36) values, mean centre scores were normalised to their native populations.

Results
Mean age of participants was 43 years, 55% were female with a mean eGFR of 77ml/min/1.73m2 and Ht-TKV of 849ml/m. 66% had PKD1 pathogenic variants. ADPKD patients uniformly reported reduced general health and less energy with the majority also experiencing poorer physical health, mental or emotional health and limitations in social functioning. 32.5% of participants experienced flank pain which was significantly and negatively correlated with the majority of KDQoL-SF subscales by multivariate analysis. Higher Ht-TKV and lower eGFR were negatively associated with reduced energy and poorer physical health respectively although not with flank pain.

Conclusion
ADPKD patients suffer with significantly reduced quality-of-life in multiple domains, exacerbated particularly by chronic pain.

Full text

Clinical Kidney Journal, 2022, vol. 0, no. 0, 1–9
https:/doi.org/10.1093/ckj/sfac144
Advance Access Publication Date: 6 June 2022
Original Article
ORIGINAL ARTICLE
Flank pain has a signicant adverse impact on quality
of life in ADPKD: the CYSTic-QoL study
Jean Winterbottom1,2, Roslyn J. Simms1,2, Anna Caroli3,
Emilie Cornec-Le Gall 4, Nathalie Demoulin 5, Monica Furlano6,
Esther Meijer7, Olivier Devuyst 5, Ron T. Gansevoort7, Yannick Le-Meur8,
Norberto Perico3, Roser Torra 6and Albert C.M. Ong 1,2
1Academic Nephrology Unit, Department of Infection, Immunity and Cardiovascular Disease, University of
Shefeld, Shefeld, UK, 2Shefeld Kidney Institute, Shefeld Teaching Hospitals NHS Foundation Trust,
Shefeld, UK, 3Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Bergamo, Italy, 4Brest University,
Inserm, UMR 1078, GGB, CHU Brest, Brest, France, 5Cliniques Universitaires Saint-Luc, Université Catholique
de Louvain Medical School, Brussels, Belgium, 6Inherited Kidney Disorders, Nephrology Department, Fundació
Puigvert, IIB Sant Pau, Universitat Autònoma de Barcelona, Barcelona, Spain, 7Department of Nephrology,
University Medical Centre Groningen, Groningen, The Netherlands and 8Brest University, Inserm, UMR 1227,
LBAI, CHU Brest, Brest, France
Correspondence to: Albert C.M. Ong; E-mail: a.ong@shefeld.ac.uk
ABSTRACT
Background. Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disorder and
a major cause of kidney failure worldwide. However, its impact on quality-of-life has not been systematically explored.
Methods. The CYSTic-QoL study was an observational study designed to study quality-of-life in adult European ADPKD
patients with an estimated glomerular ltration rate (eGFR) ≥30 mL/min/1.73 m2. A total of 465 patients were recruited
from six expert European centres with baseline data recorded, including health-related quality-of-life (HRQoL),
incorporating a Kidney Disease QoL short form questionnaire (KDQoL-SF, version 1.3), magnetic resonance imaging (MRI)
for total kidney volume (TKV) measurements and DNA for genotyping. The cohort was stratied by baseline eGFR, TKV
or genotype and correlated with HRQoL scores. Bivariate and multivariate analyses were applied to examine the
relationship between HRQoL and variables of interest. KDQoL-SF scores were calculated using an online tool provided by
the RAND organization. For 36-item short form values, mean centre scores were normalized to their native populations.
Results. The mean age of participants was 43 years and 55% were female, with a mean eGFR of 77 mL/min/
1.73 m2and height-adjusted TKV (ht-TKV) of 849 mL/min; 66% had PKD1 pathogenic variants. ADPKD patients uniformly
reported decreased general health and less energy, with the majority also experiencing poorer physical, mental or
emotional health and limitations in social functioning. A total of 32.5% of participants experienced ank pain, which
was signicantly and negatively correlated with the majority of KDQoL-SF subscales by multivariate analysis. Higher
ht-TKV and lower eGFR were negatively associated with decreased energy and poorer physical health, respectively,
although not with ank pain.
Conclusion. ADPKD patients suffer from signicantly decreased QoL in multiple domains, exacerbated particularly by
chronic pain.
Received: 4.4.2022; Editorial decision: 9.5.2022
© The Author(s) 2022. Published by Oxford University Press on behalf of the ERA. This is an Open Access article distributed under the terms of the Creative
Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution,
and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
1
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2J. Winterbottom et al.
GRAPHICAL ABSTRACT
Keywords: ADPKD, kidney function, pain, quality-of-life, total kidney volume
INTRODUCTION
Autosomal dominant polycystic kidney disease (ADPKD) is the
most common inherited kidney disease, a major cause of kidney
failure and a signicant medical and economic burden across
Europe [1,2]. Nevertheless, the impact of this major disease on
the quality-of-life (QoL) of patients with preserved kidney func-
tion has not been systematically explored.
There have been few published studies on QoL in ADPKD
based on sufciently large and representative patient cohorts.
Published data have been limited to clinical trial populations
preselected for more severe disease [3], single-centre studies
[4–6], the inclusion of patients with late chronic kidney dis-
ease (CKD; Category G4 and G5) or already on kidney replace-
ment therapy (KRT) [7,8] and the use of multiple health-related
quality-of-life (HRQoL) instruments of varying sensitivity and
specicity. Indeed, a systematic review performed in 2017 con-
cluded that only nine published studies could be included based
on the 36-item short form (SF-36) questionnaire: of note, three
of these were based on randomized controlled trials [9].
Recent studies have concluded that pain is an important but
neglected symptom in ADPKD. An international Delphi survey,
followed by a consensus meeting between patients, caregivers
and medical professionals led by the Standardized Outcomes
in Nephrology Polycystic Kidney Disease initiative, identied
four core outcomes that should be considered in future trials:
kidney function, mortality, cardiovascular disease and pain
[10,11]. Of note, pain was the highest-ranked patient-reported
outcome, reecting its importance to patients, yet it has been
variably measured in a minority (24%) of clinical trials to-date
[12]. Indeed, the prevalence of pain as a major and troubling
clinical symptom that could adversely affect QoL in ADPKD
patients is unknown [13].
The CYSTic Consortium was established in 2017 to build a
longitudinal international observational cohort of patients with
ADPKD to facilitate prospective studies of factors inuencing
the natural history of ADPKD, the impact of the disease on in-
dividual patients and the economic costs on health-care sys-
tems in adult patients with an estimated glomerular ltration
rate (eGFR) ≥30 mL/min/1.73 m2. In this article we report the re-
sults of baseline QoL in participants recruited to six European
expert ADPKD centres (CYSTic-QOL study).
MATERIALS AND METHODS
Patient recruitment and centre participation
More than 450 patients were initially recruited from six ex-
pert centres across Europe (Belgium, France, Italy, the Nether-
lands, Spain and the UK) with baseline clinical data recorded,
including HRQoL (KDQoL-SF version 1.3 questionnaire), abdom-
inal magnetic resonance imaging (MRI) for total kidney volume
(TKV) measurements and DNA for genotyping. Each study cen-
tre consented to transfer their data to an electronic database
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Flank pain and QoL in ADPKD 3
(Askimed) utilized by the study. The study was approved by a
regional ethics committee (18/EE/0247) and by the study spon-
sor, Shefeld Teaching Hospitals NHS Foundation Trust. Ethics
approval was also obtained by each participating centre within
their own country.
Inclusion and exclusion criteria
Baseline inclusion criteria were age ≥18 years, eGFR
≥30 mL/min/1.73 m2[Chronic Kidney Disease Epidemiology
Collaboration (CKD-EPI) formula], a clinical diagnosis of ADPKD
based on imaging and positive family history (modied Pei–
Ravine criteria) [14] and written informed consent. Exclusion
criteria were the use of KRT before enrollment (dialysis and
allograft) or anticipated to receive such therapy within 12
months after enrollment, participation in a clinical trial aim-
ing to modify disease outcome ≤1 year before enrollment
and signicant cardiac failure (i.e. New York Heart Associa-
tion stage IV). Clinical and laboratory measurements were
calculated and expressed as mean values with standard
deviations (SDs).
Questionnaires
Demographic and socio-economic data were collected by the use
of a specically designed questionnaire and included informa-
tion such as age, gender, marital status, ethnicity, body mass in-
dex (BMI), hypertension, ank pain, smoking status, level of ed-
ucation attained and employment status.
HRQoL
HRQoL data were collected using the KDQoL-SF version 1.3 ques-
tionnaire, which combines the disease-specic KDQoL and the
generic SF-36 [15]. A total of 12 subscales are included in the
KDQoL and 8 in the SF-36: 2 optional subscales (dialysis staff en-
couragement and patient satisfaction) in the KDQoL were omit-
ted as there were no patients on dialysis. The SF-36 is com-
posed of 36 questions organized into eight multi-item scales.
Each scale is directly transformed into a 0–100 score on the as-
sumption that each question carries equal weight. The higher
the score, the lower the disability, i.e. a score of 100 is equiva-
lent to no disability and a score of 0 is equivalent to maximum
disability. There is no total score generated for the KDQoL-SF,
although a physical component score (PCS) and a mental com-
ponent score (MCS) can be generated for the SF-36. The PCS
is derived from the rst four SF-36 domains (general health,
physical functioning, role limitations–physical, bodily pain) and
the MCS is derived from the second four domains (emotional
well-being, role limitations–emotional, social functioning and
energy/vitality).
Data from the six study centres were analysed both sepa-
rately and collectively. The scores are presented as means and
SDs and the number in parentheses shown against each sub-
scale represents the number of items in the subscale. To under-
stand centre-dependent variation, we compared the two com-
posite scores, PCS and MCS, with their country-specic general
population norms [16–20]. Population norms for France were ap-
plied to Belgium due to the lack of published information.
Genotyping
All consented patients underwent molecular genetic testing
by Sanger sequencing for PKD1 and PKD2 and/or a targeted
next-generation sequencing (NGS) panel. Patients with no
clear pathogenic variant detected after Sanger sequencing
or targeted NGS were screened for large rearrangements us-
ing multiplex ligation-dependent probe amplication and
array-based comparative genomic hybridization.
TKV analysis
MRI was performed using a standardized MRI protocol without
the use of intravenous contrast. TKV analysis was performed by
individual centres from T2 or T1-weighted (Bergamo) coronal MR
images using a variety of available methods, including manual
segmentation (Shefeld, Groningen, Brussels, Bergamo), semi-
automated manual contouring using ITK-SNAP (Brest) [21]orby
applying the ellipsoid formula (Barcelona) [22]. TKV values were
corrected for patient height (m) to generate ht-TKV (mL/m).
Patient stratication
Patients were then stratied into three groups based on
known measures or predictors of disease severity, i.e. baseline
eGFR (Group 1: >90, Group 2: 60–90, Group 3: 30–59 mL/min/
1.73 m2), ht-TKV (Group 1: <500, Group 2: 501–1000, Group 3:
>1000 mL/m) and genotype (Mutation Group 1: PKD1-truncating,
Mutation Group 2: PKD1-non-truncating, Mutation Group 3:
PKD2-no mutation detected). The eGFR groups correlated with
CKD-EPI-dened CKD classes 1–3. For TKV we divided the
cohort approximately into tertiles after adjustment for height;
a ht-TKV >650 mL/m cut-off has a predictive value for the onset
of Stage 3 CKD [23]. The genotype groups have non-overlapping
Kaplan–Meier survival curves for end-stage renal disease [24].
Statistical analysis
For each centre, all centre patient characteristics as well as clin-
ical and laboratory measurements were analysed and reported
as both means and SDs for continuous data or as numbers and
percentages for categorical data. HRQoL scores and age were
summarized using measures of central tendency and disper-
sion. Continuous data were examined and tested for normality
to decide whether parametric or non-parametric tests were to be
used. Analysis of variance (ANOVA), Student’s t-test chi-squared
test or Fisher’s exacttest, were performed as appropriate to com-
pare for statistically signicant differences between groups and
Tukeys post hoc tests were performed to indicate which of the
groups were signicantly different.
To select which variables to include in multiple regression
analysis, binary regression was performed using all of the vari-
ables of interest from Table 1as independent variables and each
of the subscales from the KDQoL-SF as dependent variables. All
the results with a signicance of P≤.25werethenincludedin
the multiple regression analysis. Bonferroni correction was ap-
plied for multiple testing. A P-value of <.05 was chosen to indi-
cate statistical signicance for the nal results.
RESULTS
Patient characteristics
The sociodemographic and baseline clinical characteristics
of the 465 participants in the CYSTic I cohort are shown
in Table 1. The mean age of the cohort was 43.2 years (SD
12.8) and included slightly more females (55%) than males.
They were predominantly white Europeans (96%) and slightly
more than half were married (52%). A minority were smokers
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4J. Winterbottom et al.
Table 1. Sociodemographic and clinical characteristics of participants
Var ia ble
All centres
(N=465) UK (n=77) Spain (n=84) Italy (n=41)
France
(n=48)
Belgium
(n=99)
Netherlands
(n=116)
Age (years), mean (SD) 43.2 43.4 42.7 44.0 47.4 41.0 43.1
(12.8) (14.0) (10.4) (10.8) (13.5) (14.0) (12.4)
Female, n(%) 256 41 48 22 27 59 59
(55.1) (53.2) (57.1) (53.7) (56.3) (59.6) (50.9)
Married (yes), n(%) 243 45 38 21 26 46 67
(52.3) (58.4) (45.2) (51.2) (54.2) (46.5) (57.8)
Ethnicity (White European), n(%) 448 71 82 41 48 96 110
(96.3) (92.%) (97.6) (100.0) (100.0) (97.0) (94.8)
BMI, mean (SD) 26.0 29.0 24.8 24.5 24.5 24.8 26.9
(6.5) (8.9) (3.2) (12.0) (4.5) (4.9) (4.9)
Highest education (university), n(%) 159 21 35 7 23 34 39
(34.2) (27.3) (41.7) (17.1) (47.9) (34.3) (33.6)
Smoker, (yes), n(%) 75 6 13 6 12 11 27
(16.1) (7.8) (15.5) (14.6) (25.0) (11.1) (23.3)
Flank pain (yes), n(%) 151 40 19 12 16 33 40
(32.5) (51.9) (22.6) (29.3) (33.3) (33.3) (34.5)
Hypertension (yes), n(%) 273 43 38 22 35 56 79
(58.7) (55.8) (45.2) (53.7) (72.9) (56.6) (68.1)
Employment (full-time), n(%) 250 43 45 27 31 52 52
(53.8) (55.8) (53.6) (65.9) (64.6) (52.5) (44.8)
eGFR (mL/min/1.73 m2), mean (SD) 76.7 69.0 81.2 79.4 66.8 86.3 73.9
(25.2) (20.8) (22.7) (21.6) (26.3) (23.1) (28.5)
ht-TKV, mean (SD) 848.9 664.5 801.9 923.5 1093.5 772.4 913.8
(621.5) (459.6) (513.7) (579.9) (655.7) (663.8) (688.5)
TKV, mean (SD) 1489.0 1149.1 1480.1 1585.6 1861.7 1323.3 1629.1
(1108.4) (794.6) (1098.3) (983.7) (1128.5) (1112.8) (1240.2)
PKD1 (%) 65.8 74.0 61.9 –a91.7 58.6 76.7
aExcluded due to large proportion of missing data.
(16%) and 54% were in full-time employment. In all, 33% re-
ported experiencing ank pain and 57% had been diagnosed
with hypertension. The mean BMI of the cohort was 26.0
kg/m2(SD 6.5), eGFR 76.7 mL/min/1.73 m2(SD 25.2), ht/TKV
848.9 mL/m (SD 621.5) and TKV 1489.0 mL (SD 1108.4). There
were no signicant differences between the study centres
for age, gender, ethnicity, marital status and hypertension.
However, there were signicant centre differences by ANOVA
for other factors such as BMI, university education, smoking
history, ank pain, full-time employment, eGFR, ht-TKV and
total TKV.
Total and centre-specic HRQoL scores
Data from each study centre were analysed separately and col-
lectively to generate the scores (Supplementary data, Table S1).
For the 10 subscores comprising the KDQoL, all study centres
recorded high scores indicating good overall HR-QoL. However,
some differences between centres were detected for individual
subscales.
For the subscales that make up the SF-36, mean scores
were high except for general health [53.70 (SD 14.82)] and en-
ergy/vitality [47.41 (SD 20.66)]. For the latter, centre scores were
lower than the norm except for the UK [58.93 (SD 21.51)] and
Spain [65.12 (SD 20.12)]. For the SF-36,Italy recorded lower scores
for most of the subscales compared with other study centres.
Standard population-based reference values (1998 USA) for
both the PCS and MCS scales are set to 50 points with an SD of
10 points [25]. Using these reference values, we observed that the
mean values for both the PCS and MCS are within these parame-
ters, with Spain having the highest PCS [51.58 (SD 7.56)] and MCS
[51.54 (SD 7.55)]. The lowest PCS values were recorded in Italy
[45.15 (SD 8.30)], with the Netherlands [43.59 (SD 5.68)] recording
the lowest MCS values.
HRQoL scores stratied by eGFR
Baseline eGFR information was available for 92% of pa-
tients (n=428). Table 2summarizes the relationship be-
tween the 20 HRQoL subscores stratied by eGFR (groups
1–3). Patients with a lower eGFR were also less likely
to be in full-time employment and reported lower sex-
ual function on the KDQoL. Signicant negative associ-
ations, which reect a reduced QoL, for three subscores
in the SF-36 relating to physical health (physical functioning,
role limitations–physical and PCS) were found in relation to
decreasing eGFR.
HRQoL scores stratied by ht-TKV
TKV information was available for 87% of patients (n=406).Sup-
plementary data, Table S2 summarizes the relationship between
the 20 HRQoL subscores when stratied by ht-TKV (groups 1–3).
Surprisingly, only one SF-36 subscore (energy/vitality) showed
a signicantly negative association, and therefore a worse QoL,
with increasing ht-TKV.
HRQoL scores stratied by genotype
Genotyping information was available in 89% of patients
(n=415). One centre (Bergamo) had minimal genotyping infor-
mation available and was therefore excluded from the analysis.
Overall, 66% of patients had PKD1 mutations and 17.6% had PKD2
mutations. There was variation noted between centres: Brest
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Flank pain and QoL in ADPKD 5
Table 2. KDQoL-SF scores by eGFR group
KDQoL
eGFR Group 1 (>90
mL/min/1.73 m2)
(n=150)
eGFR Group 2 (60–90
mL/min/1.73 m2)
(n=168)
eGFR Group 3 (30–60
mL/min/1.73 m2)
(n=110) P-value
Symptom/problem 85.03 86.81 84.14 .246
Effects of kidney disease 92.42 93.49 90.62 .127
Burden of kidney disease 86.88 85.07 81.66 .075
Work 81.56 87.65 72.90 .001
Cognitive function 83.99 83.87 84.63 .935
Social interaction 80.38 80.70 81.05 .949
Sexual function 94.76 88.83 86.03 .002
Sleep 70.30 67.91 66.67 .271
Social support 77.50 79.14 81.00 .566
Overall health 75.96 75.37 71.12 .053
SF-36
Physical function 92.70 90.77 83.03 <.000
Role–physical 88.48 86.09 78.01 .021
Pain 77.27 76.43 72.78 .226
General health 54.57 54.04 51.12 .150
Emotional well-being 65.24 65.26 64.13 .789
Role–emotional 75.65 75.83 70.68 .288
Social function 81.91 80.00 76.29 .170
Energy/vitality 49.24 47.27 43.35 .074
PCS 50.37 49.67 47.16 .005
MCS 46.26 46.17 45.52 .747
Statistically signicant values in bold (P<.05).
Table 3. Signicant multivariate results for KDQoL-SF in patients experiencing ank pain
KDQoL subscales
Unstandardized
coefcients 95% CI for coefcients
Part correlation
(part R2)
t-test for
coefcients
P-value for
coefcients
Bonferroni
correction
βSE Lower Upper
Symptom/problem list –5.217 1.472 –8.112 –2.323 –0.183 (–0.177) –3.544 <.000 0.000
Effects of kidney disease –5.510 1.279 –8.027 –2.994 –0.222 (–0.225) –4.308 <.000 0.000
Burden of kidney disease –9.399 1.978 –13.289 –5.508 –0.245 (–0.240) –4.751 <.000 0.000
Cognitive function –5.337 1.922 –9.117 –1.558 –0.145 (–0.142) –2.777 .006 0.042
Quality of social interaction –4.864 1.767 –8.339 –1.388 –0.144 (–0.142) –2.752 .006 0.030
Sleep –7.584 2.037 –11.590 –3.579 –0.194 (0.188) –3.724 <.000 0.000
SF–36 subscales
Overall health –5.402 1.940 –9.219 –1.585 –0.157 (–0.151) –2.785 .006 0.072
Physical functioning –5.677 1.740 –9.099 –2.256 –0.164 (–0.151) –3.262 .001 0.008
Role limitations–physical –12.252 3.173 –18.489 –6.014 –0.207 (–0.191) –3.862 <.000 0.000
Pain –8.572 2.239 –12.973 –4.170 –0.192 (0.185) –3.829 <.000 0.000
General health –3.760 1.646 –6.998 –0.522 –0.128 (0.124) –2.285 .023 0.184
PCS –4.550 1.302 –7.121 –1.979 –0.263 (0.258) –3.495 .001 0.010
SE, standard error.
Statistically signicant values in bold (P<.05).
had the highest percentage of PKD1 patients (91.7%) while Brus-
sels had the lowest (58.6%); the percentage of PKD2 patients var-
ied accordingly. Among the genotyped patients, 6.2% remained
genetically unresolved (no mutation detected).
Supplementary data, Table S3 summarizes the relationship
between the 20 HRQoL subscores when stratied by geno-
type mutation groups 1–3. Patients in mutation group 1 (PKD1-
truncating) had signicantly lower energy/vitality scores that
are associated with decreased QoL, mirroring the change seen
with ht-TKV group 3 with the largest kidneys (Supplementary
data, Table S2). Differences in social support and sexual func-
tion were also unexpectedly found between the three mutation
groups.
Multivariate analysis for ank pain, smoking and
gender with HRQoL scores
To select the variables to include in multiple regression analy-
sis, binary regression was performed using all of the variables of
interest from Table 1as independent variables and each of the
subscales from the KDQoL-SF as dependent variables. Using this
approach, we identied ank pain, reported by almost one-third
of patients (32.5%), as the variable is negatively associated with
the highest number (i.e. 10/20 KDQoL-SF individual subscores),
suggesting an inferior QoL, including the two SF-36 composite
scores, PCS and MCS (Table 3).
In addition, smoking was reported by 16.1% of patients
and was negatively associated with 3/20 KDQoL-SF subscores
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6J. Winterbottom et al.
FIGURE 1: KDQoL-SF scores in patients reporting ank pain (n=140) and those with no pain (n=289). Only subscores with signicant differences are shown (y-axis).
X-axis scale from 40 to 100.
Table 4. Baseline characteristics of groups reporting pain and no pain
Var ia bles Pa in [n=144 (31.0%)] (Group 1) No pain [n=305 (65.6%)] (Group 2) P-value ANOVA
Age (years), mean (SD) 43.72 (12.79) 44.23 (12.97) .885
Female, n(%) 96 (20.6) 153 (32.9) .003
Married (yes), n(%) 81 (17.4) 156 (33.5) .967
Smoking (yes), n(%) 24 (5.2) 48 (10.3) .099
BMI, mean (SD) 25.94 (6.19) 26.03 (6.73) .986
eGFR (mL/min/1.73 m2), mean (SD) 75.49 (25.51) 77.13 (25.34) .726
PKD1-truncating, n(%) 58 (40.3) 113 (37.0) .794a
PKD1-non-truncating, n(%) 42 (29.2) 87 (28.5)
PKD2-no mutation detected, n(%) 35 (24.3) 79 (25.9)
Genotype unknown, n(%) 9 (6.3) 26 (8.5)
TKV, mean (SD) 1320 (833) 1527 (1152) .322
ht-TKV, mean (SD) 815 (542) 870 (647) .603
All percentages have been calculated from the total participants (n=465). Missing data for 16 participants (3.4%).
aPearson chi-squared.
Statistically signicant values in bold (p<0.05).
(i.e. symptom/problem list, burden of kidney disease and MCS)
(Supplementary data, Table S4). Finally, we noted positive asso-
ciations for female gender in two KDQoL-SF subscores (i.e. sleep
and pain) (Supplementary data, Table S5). The highest correla-
tions (negative or positive) were reported for physical limitation
in those with ank pain, the burden of kidney disease for smok-
ers and pain for female gender (Table 3, Supplementary data,
Tables S4–S5).
HRQoL scores in groups with or without ank pain
When the cohort was divided into those who reported ank pain
(n=140) and those who did not (n=289), signicant differences
were found in 14/20 KDQoL-SF categories, 4 more domains com-
pared with multivariate analysis (Fig. 1,Table4). Absolute dif-
ferences between the mean values of both groups were >3for
all signicant subscores, with the greatest differences (>10) de-
tected for pain and role limitations–physical. Both groups were
comparable in baseline characteristics apart from a lower per-
centage of females in the group reporting pain (20.6% versus
32.9%; Table 4).
Centre-specic HRQoL mean scores normalized to
country-specic normative scores
The normative values (0–100) used in the KDQoL and SF-36 are
based on US population norms [25]. Although good correla-
tions have been found between US and European populations,
signicant variance in some domains has also been noted
[26,27]. To investigate observed centre-specic differences for
HRQoL scores relevant to pain, we calculated differences be-
tween centre PCS and MCS scores with available country-specic
SF-36 composite scores for their normal population (normative
scores) [28]. For PCS and MCS, 5/6 and 6/6 centres reported
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Flank pain and QoL in ADPKD 7
FIGURE 2: Individual centre SF-36 mean subscores normalized to population norms for PCS and MCS.
overall negative scores and therefore decreased QoL, compared
with their normal populations (Fig. 2). The largest differences
(>3) were observed for MCS in 4/6 countries, while for PCS this
was observed in only 2/6 countries (Italy, France). The smallest
differences for both PCS and MCS were observed in the UK and
Spain.
DISCUSSION
In this large multicentre study of ADPKD patients with an
eGFR ≥30 mL/min/1.73 m2recruited from six major Euro-
pean countries, we report signicant impairment in QoL mea-
sures affecting multiple domains using a validated HRQoL
questionnaire. ADPKD patients consistently report poorer gen-
eral health, less energy, poorer physical mental and emotional
health and limitations in social functioning. These differences
are clearly distinct aetiologically from those related to late-
stage kidney disease (eGFR <30 mL/min/1.73 m2)orKRT.A
moderate reduction in eGFR (30–60 mL/min/1.73 m2)wasit-
self associated with poorer physical health, decreased sex-
ual health and decreased ability to work in full-time employ-
ment compared with patients with near-normal eGFR (60–90,
>90 mL/min/1.73 m2). These differences related to declining kid-
ney function have been reportedin a previous study [6], although
not in others [3,8]. However, the negative ndings were either
based on patients recruited into two clinical trials (HALT A and
B) [3] or had a signicant number of older patients (26%, mean
age 52 years) with an eGFR >30 mL/min/1.73 m2[8], which could
have confounded the analysis.
An unexpected nding was the frequency of ank pain, a
symptom reported by 32.5% of participants, which was indepen-
dent of kidney function (eGFR), kidney size (TKV) or genotype.
The pain was signicantly negatively correlated with 10/20 sub-
scores of the KDQoL-SF questionnaire reecting a reduced QoL
in these areas. Additional differences in both sexual and social
function were noted when patient groups with and without pain
were compared. Although patients with the largest kidneys (ht-
TKV >1000 mL/m) and associated genotype (PKD1-truncating)
reported less energy compared with those with smaller kidneys,
there was no linear relationship between kidney volume and
pain, as previously reported [3]. Our study nonetheless reveals
that kidney pain is common, independent of kidney volume,
function or genotype, but associated with signicantly poorer
QoL in patients experiencing it.
The variation in individual QoL scores between centres led
us to question whether some of the differences observed could
relate to differences between the native European populations.
Using published general population country-specic composite
scores, we found negative differences and therefore decreased
QoL for PCS in ve of six centres and MCS in all six centres [28].
However, if a threshold difference of >3 is applied for clinical
signicance, fewer centres were found to be different from their
population norms, especially for PCS (two of six).The greater dif-
ferences in MCS (four of six) suggest that taken as a whole, this
group of patients is affected more by the domains contributing
to MCS rather than PCS. The UK and Spain both showed the least
difference for PCS and MCS, whether applying standard (US) or
country-specic normative values. Similarly, the lowest scores
for PCS and MCS were recorded in Italy and the Netherlands,
respectively, regardless of whether standard or country-specic
normative values were used. These comparisons lead us to con-
clude that the differences noted between the centres are not ob-
viously related to country-specic differences.
The factors leading to poorer QoL in ADPKD patients with an
eGFR ≥30 mL/min/1.73 m2are multiple. The two major factors
identied, moderate decline in eGFR and ank pain, account
for some, though not all, of the measured changes. It seems
likely that other specic psychosocial factors such as loss of a
rst-degree relative due to ADPKD, worry about transmitting
the disease to the next generation (genetic ‘guilt’), which were
not measured in the KDQoL-SF instrument, are important and
merit further study [6]. Other physical factors (e.g. signicant
polycystic liver volume enlargement) that were not measured in
this study have been found to contribute to poorer QoL in other
cohorts [9]. Finally, it would be of interest to determine whether
the availability of a disease-modifying treatment (tolvaptan),
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8J. Winterbottom et al.
which has since become available in all six countries repre-
sented in this cohort, has had a measurable effect on QoL
reporting.
Our study has some limitations. First, this was a cross-
sectional study and therefore causal relationships between the
associations found must remain speculative.There was also sig-
nicant variability between centres for some baseline character-
istics (Table 1), which may have reduced the power of the study
to detect important differences. Conversely, this is presently the
largest international academic-initiated observational study in
ADPKD and our current ndings should be relevant to more than
one country, at least in Europe. Second, the participants were
largely racially homogeneous (White Caucasian), so our results
may not apply to other ethnic populations. Third, we were not
able to exclude the potential contribution of advanced polycys-
tic liver disease to QoL in some patients. Finally, the KDQoL-SF
instrument did not include detailed questions regarding pain,
analgesic use or psychosocial risk. All these issues could be ex-
plored in future studies with an amended protocol including dif-
ferent racial groups.
In summary, we report signicantly decreased QoL in mul-
tiple domains within a large and representative cohort of Eu-
ropean ADPKD patients. A signicant contributing factor ap-
pears to be ank pain. We suggest that a greater aware-
ness of pain as a common symptom experienced by ADPKD
patients is needed and further research into better ways of
managing pain in ADPKD should be a priority.
SUPPLEMENTARY DATA
Supplementary data are available at ckj online.
ACKNOWLEDGEMENTS
We thank all participants for their generous contributions to the
success of this study.
FUNDING
Establishment of the CYSTic cohort was funded in part by an
unrestricted educational grant from Otsuka Europe and research
grants from the Shefeld Kidney Research Foundation and the
PKD Charity (UK).
AUTHORS’ CONTRIBUTIONS
All authors obtained consent, recruited patients, and collected
and contributed data from their centre. J.W. performed the pri-
mary data analysis. A.C.M.O. obtained funding and supervised
and coordinated the study. J.W. and A.C.M.O. wrote the article.
All authors read and approved the nal manuscript.
CONFLICT OF INTEREST STATEMENT
R.T. is a member of the CKJ editorial board. The results presented
in this article have not been published previously in whole or
part except in abstract form.
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