Background Screening psoriatic arthritis remains a challenge. A few dedicated tools have been developed in different settings however direct comparative data is limited.
Objectives To compare screening properties of a new instrument [PsoQ], inspired by both ASAS recommendations for early diagnosis of spondyloarthritis and ACR criteria for rheumatoid arthritis, to three others developed in the setting of dermatology practice [PAQ, PASE and PEST].
Methods Consecutive subjects diagnosed with psoriasis by the dermatologist were submitted the four questionnaires. Subjects with scores above the reported threshold values and a set value for the new instrument, designated as screened positive, were offered rheumatological assessment to search for psoriatic arthritis. Screening properties of the four tools were compared.
Results 371 patients with a mean (SD) age of 39.1 (16.9) were included [204 women (54.9%)]. Predominant psoriasis phenotype was psoriasis vulgaris (78%); prevalence of nail involvement was 15.6% and of scalp lesions 33.7%.
103 patients (27.0%) were screened positive using either of the four questionnaires: 25 (6.8%) using the PAQ questionnaire, 55 (14.8%) with the PASE questionnaire and 41 (11.1%) by the PEST questionnaire. 52 (14.0%) reported features of inflammatory back pain and 32 (8.6%) reported features of inflammatory peripheral arthritis and accordingly 68 (18.3%) were screened positive by the PsoQ.
In total, 10 patients were identified as psoriatic arthritis (prevalence 2.7% (95%CI: 1.1%; 4.3%). Predominantly axial phenotype was present in 5 subjects and peripheral arthritis phenotype in five.
Sensitivities (SE) and specificities (SP) of the four questionnaires ranged between 70% and 100% for SE and between 83.9% and 94.4% for SP. SE was the highest using PsoQ (100%) while SP was the highest using PAQ7 (94.4%).
Positive predictive values (PPV) were low, between 12.7% and 20.0% while negative predictive values (NPV) were high, between 98.6% and 100.0%. The highest PPV was achieved with PAQ7 (20%) and the highest NPV (100%) was obtained with PsoQ.
Positive likelihood ratios (PLR) were moderate ranging from 5.3 to 8.8 and negative likelihood ratios (NLR) ranged between 1.9 and 4.5.
Conclusions The four tools showed similar screening properties. Subjects with scores above threshold values need referral for rheumatological assessment.
Limitations in Screening Instruments for Psoriatic Arthritis: A Comparison of Instruments in Patients with Psoriasis. Walsh JA. et al. J Rheumatol 2013;40:287–93
Disease assessment in psoriatic spectrum: a modular approach for use in routine clinical practice. Wajed J. et al. Ann Rheum Dis 2013;0:1–2.
Acknowledgement St Joseph University Council for scientific research for main funding of the study
Abbvie pharmaceuticals for partial funding of the study
Disclosure of Interest None declared