nail involvement as a predictor of concomitant psoriatic arthritis in patients with psoriasis

These articles have been accepted for publication in the British Journal of Dermatology and are currently being edited and typeset. Readers should note that articles published below have been fully refereed, but have not been through the copy-editing and proof correction process. Wiley-Blackwell and the British Association of Dermatologists cannot be held responsible for errors or consequences arising from the use of information contained in these articles; nor do the views and opinions expressed necessarily reflect those of Wiley-Blackwell or the British Association of Dermatologists This article is protected by copyright. All rights reserved. Accepted Date : 02-Jul-2014 Article type : Epidemiology and health services research Nail Involvement as a Predictor of Concomitant Psoriatic Arthritis in Patients with Psoriasis

A. Langenbruch1, M.A. Radtke1, M. Krensel1, A. Jacobi1, K. Reich2, M. Augustin1

1 IVDP - Institute for Health Services Research in Dermatology and Nursing, University Medical Center Hamburg-Eppendorf, Hamburg, Germany

2 Dermatologikum Hamburg, Hamburg, Germany

corresponding author: Anna Langenbruch IVDP - Institute for Health Services Research in Dermatology and Nursing University Medical Center Hamburg-Eppendorf Martinistr. 52 | D-20246 Hamburg | Germany tel: +49 (0) 40 7410 53 942 | fax: +49 (0) 40 7410 55 348 | email: [email protected] running head: Nail Involvement Predicts Psoriatic Arthritis funding sources: This study was supported by research grants from MSD Sharp & Dohme GmbH, Haar, Germany. conflict-of-interest disclosures: M Augustin, A Jacobi, MA Radtke, K Reich have received funding from MSD Sharp & Dohme for research and were invited speakers and consultants for this company. M Krensel and A Langenbruch have no conflicts of interest to declare.

This article is protected by copyright. All rights reserved.

What’s already known about this topic? In dermatological care there is a considerable rate of undiagnosed Psoriatic Arthritis (PsA) among

psoriatic patients. Indicators for the detection of PsA are needed for earlier diagnosis and management.

The predictive value of clinical and patient reported outcomes for PsA is controversial. Scalp psoriasis

and nail disease are postulated as predictors of PsA incidence.

What does this study add?

Nail psoriasis and inpatient hospital treatment due to psoriasis are the main indicators of concomitant

PsA.

Abstract

Background

Patients with Psoriatic Arthritis (PsA) suffer from increased burden of disease and impairments in quality

of life. Early detection and treatment of PsA could contribute to the prevention of clinical and radiologic

progression.

Objectives

Analyse the predictive value of clinical and patient reported outcomes for concomitant PsA in a population

based cohort of patients with psoriasis.

Methods

Retrospective analysis of data from three independent national cross-sectional studies on health care in

psoriasis and PsA, conducted in Germany in the years 2005, 2007 and 2008 was performed. N = 3,520

patients with psoriasis were included by dermatologists and n = 2,449 patients via the German patient

advocacy group for psoriasis. In all studies psoriasis history, clinical findings, PsA, nail involvement,

health care and patient reported outcomes were collected with standardized questionnaires.

Results

In the regression model on n = 4,146 patients the strongest predictors for concomitant PsA were nail

involvement (OR 2.93, 95 % confidence interval (CI) 2.51 - 3.42, p < 0.001) and inpatient hospital

treatment (OR 1.63, 95 % CI 1.38 - 1.93, p < 0.001). By contrast, scalp involvement was not a significant

predictor.


Conclusions

Psoriatic patients seen by dermatologists and in patient advocacy groups show clinical indicators of PsA,

the most predictive being nail disease. In practice, a comprehensive assessment of clinical findings

associated with PsA is needed.

Introduction

Psoriatic arthritis (PsA) is a psoriasis-related chronic, systemic inflammatory condition with typical signs

and symptoms both of psoriasis and arthritis1. Two independent studies from Germany have resulted in

almost similar prevalence of 20.6 % and 19.0 %, respectively, in patients with psoriasis referring to

dermatologists2,3.

Patients with PsA have reduced quality of life and functional capacity compared with psoriatic patients in

general and - even more - compared with healthy controls4,5. In half of the patients, aggravation of joint

damage, which may lead to deformities, has been noted within the first two years of disease6. Since joint

disease can lead to irreversible bone damage, there is an indication for early detection and treatment of

any arthritic affection in psoriasis. For this, an increasing number of dermatologists are dedicated to

identify signs and suspicious symptoms for PsA. Vice versa, rheumatologists, who may see markedly

different subgroups of patients with PsA should focus on skin lesions associated with PsA. For both

groups of physicians, indicators and predictors of PsA permitting early detection of disease are of

considerable clinical interest. If validated properly, they may help to identify patients at risk of detoriation.

Especially nail involvement, scalp affections and intergluteal/perianal psoriatic lesions are associated with

a higher likelihood of developing PsA and are therefore regarded as main predictors of PsA7,8. For

instance, nail lesions were found in about 40 - 45 % of patients with psoriasis only and in about 87 % of

patients with PsA9,10.

The nail is just as much a part of the anatomical functional unit of the enthesis as of the skin11. The fascia

of the enthesis transitions into and is continuous with the nail radix12. McGonagle and Tan used MRI of

the finger to study the anatomical correlations. Histologically, and with high-resolution MRI, one could see

that the extensor tendon which crosses the distal interphalangeal (DIP) joint is connected with the nail

radix and matrix via tendinous fibers surrounding the radix13. In PsA there is nearly always enthesitis of

the DIP joint in the early phase of disease. The inflammatory reaction may be severe, even affecting the

nail matrix. This close relationship between the nail, tendinous attachment to the bone, and periosteum

may explain why patients with psoriatic arthritis, who typically have inflammatory changes affecting the

DIP joint, often develop inflammation of the nail, too.

PsA is often prone to be overlooked3. Since more than 80 % of patients with PsA present symptoms of

psoriasis before developing symptoms of PsA14, dermatologists are in a unique position to detect PsA


earlier in the disease process through regular, routine screening of psoriasis patients. Therefore, active

monitoring of psoriasis patients for signs of joint or arthritic involvement and familiarity with PsA

screening, diagnosis and treatment options can help dermatologists to positively impact the clinical

course of psoriatic disease. Distinguishing clinical features of PsA include nail involvement in the vast

majority of cases. The severity of nail involvement is determined by the site of the inflammatory reaction.

If the nail matrix is involved, there may be development of indentations (pitting), leukonychia, red patches

in the lunula, and onychodystrophy. Severe nail psoriasis can result in the crumbling of the nail. If the nail

bed is affected, typical “oil spots”, splinter hemorrhage, onycholysis, and subungual parakeratosis and

hyperkeratosis can be observed.

The main objective of the present analysis was the identification of significant clinical and patient-reported

predictors for concomitant psoriatic arthritis in a population based cohort of patients with psoriasis. For

this purpose we performed an analysis of data, derived from 3 independent national cross-sectional

studies on health care in psoriasis and psoriatic arthritis, conducted in Germany in the years 2005, 2007

and 2008.

The research questions raised were the following:

1. How do patients with PsA, who are treated in dermatology settings, differ from patients without

PsA?

2. Which are the strongest predictors of PsA?

Methods

Study design

This is a retrospective predictor analysis of three psoriasis patient cohorts from three independent

national cross-sectional studies on health care in psoriasis and PsA conducted in the years 2005, 2007

and 2008. Patients were included by dermatological practices and clinics (PsoHealth 1; 20053 and

PsoHealth 2; 20072) and via the patient advocacy group “Deutscher Psoriasis Bund (DPB)”, the largest

German patient organisation for psoriasis (PsoReal; 2008)15.

In all three studies a data set on psoriasis history, clinical findings including PsA, nail involvement, health

care, and patient reported outcomes were collected with standardized questionnaires filled in by patients

and their respective dermatologists (PsoHealth 1 and 2) and exclusively by the patients (PsoReal).

Approval of the local ethics committee of the Hamburg Board of Physicians was obtained for all three

studies.


Centers, patients and outcome measures

PsoHealth 1 and 2 involved 48 (PsoHealth 1)3 and 129 (PsoHealth 2)2 dermatological practices and

outpatient clinics that recruited 1,511 (PsoHealth 1) and 2,009 (PsoHealth 2) patients with plaque-type

psoriasis. PsoReal was performed with 2,449 members of the DPB15 suffering from psoriasis.

The prevalence data of PsA of these studies have been published elsewhere2,3,16. Moreover, the

outcomes on quality of health care have also been previously published15,17,18.

Prospectively assigned indicators to evaluate differences between patients with and without PsA included

a variety of epidemiological, patient-reported and clinical parameters: age, sex, years since first

diagnosis, health-related quality of life assessed by the Dermatology Life Quality Index (DLQI), health

state assessed by EQ-5D Visual analogue scale (EQ-5D VAS), nail involvement, scalp psoriasis,

inpatient treatment within the last 5 years due to psoriasis, family history of psoriasis, days off work due to

psoriasis in the last 12 months, mean severity of psoriasis assessed by Psoriasis Area and Severity Index

(PASI) (PsoHealth 1 and 2 only) (Table 1).

Assessment of psoriatic arthritis

PsA was assessed differently in all three studies due to their different designs (Table 2).

Psoriatic patients with probable PsA were classified as group “PsA probable”. Accordingly, patients were

included in the group “PsA not probable” only if they did not show any of the symptoms specific for PsA.

In accordance with this conservative approach uncertain cases (e. g. confirmation of relevant symptoms

without a statement of a physician about a diagnosis or a high probability of PsA) were excluded from

analysis.

Statistical analysis

All data was described with standard statistical parameters (frequencies for categorical data, mean value,

standard deviation for continuous data).

The significance tests focused on the comparison of two groups: patients with PsA and those without

PsA. Therefore, a combined approach was chosen in order to detect differences between those groups.

Most analyses were performed for the combined sample. Separate analyses for samples were conducted

if a variable was not included in all studies. Differences between groups with regard to frequencies were

analysed by chi-squared tests for independence. Means of two groups were compared by unpaired t-

tests. In order to take relations of the variables into account, binary logistic regression models were

additionally calculated for variables that were assessed in all the studies.

Differences with a probability of a type I (alpha) error of ≤ 0.05 were considered as statistically significant

in all analyses. It is important to notice the statistical power is high due to the large sample size.


Therefore, very weak affects can achieve statistical significance. Hence, effect sizes are important

indicators of whether the findings have substantive significance19. Therefore, each unpaired t-test was

supplemented by effect-size determination (Cohen’s d). According to Cohen, sizes of 0.2, 0.5 and 0.8

respectively represent weak, medium and strong effects in unpaired t-tests20. Each chi-squared test was

also supplemented by effect-size determination (Cohen´s ω). Effect sizes of 0.1, 0.3 and 0.5 are

considered small, medium, and large respectively in ω. Missing values were not replaced.

Data management and descriptive data analysis was performed using SPSS version 20.0 for Windows.

Results

In total, 4,863 patients with psoriasis and verified diagnostic information about the presence or absence of

PsA were included with a mean age of 52.9 years; 43 % were female in the combined sample. 30.1 % of

those (n = 1,465) were classified as suffering from PsA.

The differences in the tested variables between psoriasis patients with PsA and those without PsA were

all significant. However, a medium effect size was only found for the variables nail involvement, health

state and years since first diagnosis: Patients with PsA had higher frequencies of nail involvement (72.5

% vs. 41.5 %, ω = 0.28) (Table 3). They were also showing a lower health state (EQ-5D VAS = 55.7 ±

22.4 vs. 67.1 ± 20.8, d = 0.53) and more years since first diagnosis of psoriasis (29.4 ± 15.7 vs. 22.4 ±

16.2 years, d = 0.44) (Table 4).

In the regression model the strongest predictors for the presence of PsA were nail involvement (OR 2.93,

95 % confidence interval (CI) 2.51 - 3.42, p < 0.001) and inpatient hospital treatment (OR 1.63, 95 % CI

1.38 - 1.93, p < 0.001) (Table 5). The tested variables explained a variance of 19.7 %.

Discussion

This study was conducted to determine parameters associated with concomitant PsA in a large cohort of

psoriatic patients in Germany. The analysis suggests that these patients show typical demographic

characteristics of psoriasis as detected by secondary analysis of health insurance data21 as well as by

studies from other countries22,23.

The rationale for the current study was the observation from previous studies that patients with PsA suffer

from increased burden of disease, striking impairments in quality of life, a higher loss of working days and

a greater consumption of health care resources24,25. For this, the early detection and accurate treatment

of PsA most probably will be beneficial to patients, to the payers and to society. In particular, the


avoidance of disease progression and irreversible bone damage is a major goal of PsA treatment26. Thus,

the identification of valid clinical factors predicting PsA in patients with psoriasis of the skin is crucial. To

date, studies evaluating these factors have mostly been performed on subgroups of patients identified by

rheumatologists8. However, a great proportion of patients with psoriasis in Germany is in the care of

dermatologists and GPs. Therefore, the current predictor analysis focused on these patients rather than

on those filtered by processes leading to rheumatologists. Hence, in terms of external validity the results

cannot be generalised to those patients with psoriasis who are not in dermatological treatment.

Differently from the prospective study by Wilson at al.8 no predictors of onset of PsA but of concomitant

PsA were analysed. Since there is no long-term data for prospective analysis available, the present study

focused on patients investigated in cross-sectional studies of three large German national surveys for

psoriasis. Another limitation is the missing differentiation of particular features of nail psoriasis such as

pitting and onycholysis. Further studies should explore whether different signs of nail disease show

different predictive value.

In order to rule out a detection bias due to unclear PsA, all analyses were performed with valid groups:

patients presenting a high probability versus those showing a very low probability of PsA. In accordance

with the studies by Wilson et al.8 the presence of nail psoriasis is predictive for PsA in this study.

This result could be explained by the Koebner response phenomenon in which microdamage or trauma

may be responsible for the skin lesions in psoriasis, analogously, a Koebner response could be

responsible for the development of both nail disease and PsA. Indeed, there are microanatomical

similarities between the skin and the enthesis: both integrate two different tissue types (in skin, the

epidermis and dermis; in the enthesis, bone and fibrocartilage), dissipate stress and promote tissue union

by increasing the surface area of contact between the tissues.27 Furthermore, there is a close functional

integration between the nail, the joint and its associated tendons and ligaments, which likely explains the

known association between the DIP joint arthritis and nail disease.28 The nail is intimately linked with the

network of enthesis fibres extending from the extensor tendon and collateral ligament enthesis that

anchor the nail directly to the skeleton. Therefore, from a tissue-specific factor it seems that nail dystrophy

and PsA are anatomically linked to enthesopathy.29

Recently, the prevalence of scalp involvement was found to be similar in newly diagnosed PsA patients

and those with psoriasis only30. This fits to our finding of scalp psoriasis not being a significant predictor of

PsA. The contradictory results in literature could be explained by different populations of psoriatic patients

with some studies including patients with higher levels of skin involvement and others predominantly in

rheumatological care including patients with little skin involvement.

With respect to the divergent outcome of the study by Wilson et al. and the present study, it cannot be

excluded that scalp involvement is indeed an early indicator for the risk of PsA development8, which

cannot be detected anymore when PsA is manifest2,3,16.


In addition to the subgroup comparisons of patients with versus without PsA, a multiple regression

analysis was conducted to take relations of the independent variables into account. The tested

parameters differing in the subgroup comparisons might support the validity of the predictors. Due to an

explained variance of 19.7 % further variables should be analysed to predict PsA in patients with

psoriasis. It would be valuable to test the hypothesis raised in this study with prospective data, like those

being attained by current registries.31,32

In conclusion, five out of nine tested variables significantly contribute to the prediction of PsA. These

parameters are helpful for clinical management of patients with psoriasis. They can be easily applied

under routine conditions. Thus with just few clinical considerations the detection of PsA and consequently

the quality of care of patients with PsA can be improved.

References

1 Simonić E, Peternel S, Stojnić-Soša L et al. Negative and positive life experiences in patients with

psoriatic arthritis. Rheumatol Int 2013; 33(6): 1587–93. 2 Radtke MA, Reich K, Blome C et al. Prevalence and clinical features of psoriatic arthritis and joint

complaints in 2009 patients with psoriasis: results of a German national survey. J Eur Acad Dermatol Venereol 2009; 23(6): 683–91.

3 Reich K, Krüger K, Mössner R, Augustin M.Epidemiology and clinical pattern of psoriatic arthritis in Germany: a prospective interdisciplinary epidemiological study of 1511 patients with plaque-type psoriasis. Br J Dermatol 2009; 160(5): 1040–7.

4 Zachariae H, Zachariae R, Blomqvist K et al. Quality of life and prevalence of arthritis reported by 5,795 members of the Nordic Psoriasis Associations. Data from the Nordic Quality of Life Study. Acta Derm Venereol 2002; 82(2): 108–13.

5 Taylor WJ. Impact of psoriatic arthritis on the patient: through the lens of the WHO International Classification of Functioning, Health, and Disability. Curr Rheumatol Rep 2012; 14(4): 369–74.

6 Gladman DD. Mortality in psoriatic arthritis. Clin Exp Rheumatol 2008; 26(5 Suppl 51): S62-65. 7 Gelfand JM, Gladman DD, Mease PJ et al. Epidemiology of psoriatic arthritis in the population of

the United States. J Am Acad Dermatol 2005; 53(4): 573–7. 8 Wilson FC, Icen M, Crowson CS et al. Incidence and clinical predictors of psoriatic arthritis in

patients with psoriasis: a population-based study. Arthritis Rheum 2009; 61(2): 233–9. 9 Gladman DD, Antoni C, Mease P et al. Psoriatic arthritis: epidemiology, clinical features, course,

and outcome. Ann Rheum Dis 2005; 64 (Suppl 2): ii14–ii17. 10 Gladman DD, Anhorn KA, Schachter RK, Mervart H.HLA antigens in psoriatic arthritis. J Rheumatol

1986; 13(3): 586–92. 11 Tan AL; Benjamin M, Toumi H et al. The relationship between the extensor tendon enthesitis and

the nail in distal interphalangeal joint disease in psoriatic arthritis – a high resolution MRI and histological study. Rheumatology 2007; 46: 253–256.

12 McGonagle D. Enthesitis: an autoinflammatory lesion linking nail and joint involvement in psoriatic disease. J Eur Acad Dermatol Venereol 2009; 23 (Suppl. 1): 9–13.

13 Tan AI, Granger AJ, Tanner SF et al. A high-resolution magnetic resonance imaging study of distal interphalangeal joint arthropahy in psoriatic arthritis and osteoarthritis: are they the same? Arthritis Rheum 2006; 54:1328–33.

14 Armstrong AW, Schupp C, Bebo B.Psoriasis Comorbidities: Results from the National Psoriasis Foundation Surveys 2003 to 2011. Dermatology 2012; 225: 121–6.


15 Langenbruch AK, Radtke MA, Augustin M. Quality of psoriasis care from the patients' perspective-results of the national health care study PsoReal. Eur J Dermatol 2012; 22(4): 518–24.

16 Radtke MA, Langenbruch AK, Schaefer I et al. Nail psoriasis as a severity indicator: results from the PsoReal study. Patient Relat Outcome Meas 2011; 2: 1–6.

17 Augustin M, Krüger K, Radtke MA et al. Disease severity, quality of life and health care in plaque-type psoriasis: a multicenter cross-sectional study in Germany. Dermatology 2008; 216(4): 366–72.

18 Augustin M, Reich K, Reich C et al. Quality of Psoriasis Care in Germany – Results of the National Study PsoHealth 2007. J Dtsch Dermatol Ges 2008; 6(8): 640–6.

19 Crosby RA, DiClemente RJ, Salazar LF.Analytic Techniques for Observational Research. In: Research Methods in Health Promotion (Crosby RA, DiClemente RJ, Salazar LF, eds). San Francisco: John Wiley & Sons, 2006; 317–46.

20 Cohen J. The statistical power analysis for the behavioral sciences, 2nd ed. Hillsdale, NJ: Erlbaum, 1988.

21 Augustin M, Reich K, Glaeske G et al. Co-morbidity and age-related prevalence of psoriasis: Analysis of health insurance data in Germany. Acta Derm. Venereol. 2010; 90(2): 147–51.

22 Jones SM, Armas JB, Cohen MG et al. Psoriatic arthritis: outcome of disease subsets and relationship of joint disease to nail and skin disease. Br J Rheumatol 1994; 33(9): 834–9.

23 Williamson L, Dalbeth N, Dockerty JL et al. Extended report: nail disease in psoriatic arthritis--clinically important, potentially treatable and often overlooked. Rheumatology 2004; 43(6): 790–4.

24 Mease PJ. Assessing the impact of psoriatic arthritis on patient function and quality of life: lessons learned from other rheumatologic conditions. Semin Arthritis Rheum 2009; 38(4): 320–35.

25 Husted JA, Gladman DD, Farewell VT, Cook RJ.Health-related quality of life of patients with psoriatic arthritis: a comparison with patients with rheumatoid arthritis. Arthritis Rheum. 2001; 45(2): 151–8.

26 Veale DJ. New therapies and new goals for psoriatic arthritis. Arthritis Rheum 2011; 63(4): 874–6. 27 McGonagle D, Tan AL, Benjamin M: The biomechanical link between skin and joint disease in

psoriasis and psoriatic arthritis: what every dermatologist needs to know. Ann Rheum Dis 2008; 67: 1–4.

28 McGonagle D, Tan AL, Benjamin M: The nail as a musculoskeletal appendage – implications for an improved understanding of the link between psoriasis and arthritis. Dermatology 2009; 218: 97–102.

29 McGonagle D. Enthesitis: an autoinflammatory lesion linking nail and joint involvement in psoriatic disease. J Eur Acad Dermatol Venereol 2009; 23 (Suppl 1): 9–13.

30 Haroon M, Kirby B, FitzGerald O. High prevalence of psoriatic arthritis in patients with severe psoriasis with suboptimal performance of screening questionnaires. Ann Rheum Dis 2013; 72(5): 736–40.

31 Papp KA, Strober B, Augustin M et al. PSOLAR: design, utility, and preliminary results of a prospective, international, disease-based registry of patients with psoriasis who are receiving, or are candidates for, conventional systemic treatments or biologic agents. J Drugs Dermatol 2012; 11(10): 1210–7.

32 Augustin M, Spehr C, Radtke MA et al. German psoriasis registry PsoBest: objectives, methodology and baseline data. J Dtsch Dermatol Ges 2014; 12(1): 48–57.


Tables

Table 1: Variables included as possible predictors for PsA

PsoHealth 1

20053

PsoHealth 2

20072

PsoReal

200815

Setting dermatologist

offices

dermatologist

offices

direct approach to

patients

Age x x x

Sex x x x

Years since first diagnosis of psoriasis x x x

Health-related quality of life (DLQI) x x x

Subjective health state (EQ-5D-VAS) x x x

Nail involvement x x x

Psoriasis of the head PASI head

yes / no

PASI head

yes / no

Psoriasis lesions in

the scalp due to

patient

documentation in a

body scheme

Inpatient treatment in the last 5 years x x x

Patients with family history of psoriasis x x x

Days off work due to psoriasis in the last year x x x

Psoriasis area and severity index (PASI) x x -

3 Reich K et al. 2009 2 Radtke MA et al. 2009 15 Langenbruch AK et al. 2012


Table 2: Assessment of PsA in the three studies

PsA in ‚PsoHealth 1‘

Recruitment by dermatologists all over Germany.

Diagnostic algorithm:

If at least one of the key criteria for joint involvement was met, patients were recommended to consult a

rheumatologist. The rheumatological evaluation clarified whether the patient had a PsA or not.

PsA in ‚PsoHealth 2‘

Recruitment by dermatologists all over Germany, no rheumatologists involved.


If a PsA had been previously confirmed the diagnosis was adopted without further questions. Otherwise:

Does the patient suffer from joint complaints? If this item has been affirmed, the dermatologist answered

specific questions about history and clinical symptoms relevant for PsA. This list of symptoms followed

modified recommendations of the international GRAPPA group (Group for Research and Assessment in

Psoriasis and Psoriatic Arthritis, 2007)24. The presence of PsA was thus assessed by the dermatologist.

PsA in ‘PsoReal’

Recruitment by postal assessment of German advocacy group members, no rheumatologist involved.


Because no medical diagnosis was included in this study, typical symptoms were recorded in a

questionnaire derived from study #2. For better validity beyond this assessment, the patients were

additionally asked whether the PsA had been diagnosed by a physician.


Table 3: Clinical characteristics and results of the chi-squared test for independence in patients

with probable and improbable PsA

PsA not probable PsA probable

p-

value

MV*

(n)

n % n % χ2 df ω**

Site of the psoriasis: nail

involvement 1 1,411 41.5 1,062 72.5 392.43 1 .000 0.28

Site of the psoriasis: head 56 2,375 70.5 1,093 75.9 14.45 1 .000 0.06

Gender of the patient:

female 79 1,398 41.9 659 45.6 5.61 1 .018 0.03

Inpatient treatment (at least

once in the last 5 years) 184 606 18.4 484 34.9 149.44 1 .000 0.18

Relatives with psoriasis 46 1,338 39.7 682 47.3 24.02 1 .000 0.07

*missing values

**effect size


Table 4: Descriptive statistics and results of the t-test for independent samples of patients with

probable versus improbable psoriatic arthritis (PsA) pooled from three German nationwide

cohorts

MV* n M±SD t df p-

value d´**

Age PsA not probable 33 3365 51.9 ± 14.7

-7.92 3,272.03 .000 0.24

PsA probable 12 1453 55.2 ± 12.3

Years since

first diagnosis

PsA not probable 120 3278 22.4 ± 16.2 -13.92 2,767.07 .000 0.44

PsA probable 47 1418 29.4 ± 15.7

DLQI PsA not probable 64 3334 6.9 ± 6.2

-7.97 2,430.04 .000 0.26

PsA probable 25 1440 8.6 ± 7.1

Health state

(EQ-5D VAS)

PsA not probable 166 3232 67.1 ± 20.8 16.27 2,533.77 .000 0.53

PsA probable 46 1419 55.7 ± 22.4

Severity

(PASI)*

PsA not probable 41 2486 10.3 ± 8.8 -3.60 892.34 .000 0.17

PsA probable 11 638 12.0 ± 10.3

* assessed in PsoHealth 1 and 2 only

** Missing values (n)

***effect size


Table 5: Logistic regression analysis on variables potentially predicting PsA in a pooled

nationwide data set of patients with psoriasis (n = 4,146), Nagelkerkes R-Square = .197

Predictor variablea Bb SE

p-

value OR CI 95 %

Age .006 .003 .044 1.01 1.00-1.01

Sex -.144 .076 .060 0.87 0.75-1.01

Time since first diagnosis .018 .003 .000 1.02 1.01-1.02

DLQI .007 .006 .271 1.00 0.99-1.02

EQ-5D-VAS -.018 .002 .000 0.98 0.98-0.99

Scalp psoriasis .064 .086 .457 1.07 0.90-1.26

Nail involvement 1.07 .079 .000 2.93 2.51-3.42

Inpatient hospital treatment due to psoriasis .491 .085 .000 1.63 1.38-1.93

Relatives with psoriasis 0.10 .076 .189 1.11 0.95-1.28

a Age = years; Sex: male = 1, female = 0; Time since first diagnosis: years; DLQI: scale from 0 = minimum to 30 = maximum QoL

impairment; EQ-5D-VAS: scale from 0 = worst health state to 100 = best health state; scalp psoriasis: scalp affected = 1, not

affected = 0; nail involvement: nails affected = 1, not affected = 0; inpatient treatment due to psoriasis at least once in the last 5

years: yes = 1, no = 0; relatives with psoriasis yes = 1, no = 0 b B, regression coefficient; SE, standard error; OR, Odds Ratio (exponentiation of the B coefficient); CI, Confidence Interval

nail involvement as a predictor of concomitant psoriatic arthritis in patients with psoriasis

Documents