RESUMO
Delaying diagnosis of psoriatic arthritis (PsA) can lead to poor quality of life and disability. The purpose of this study is to identify simple questions for dermatologists to screen psoriasis patients for psoriatic arthritis. Data regarding psoriasis and arthritis were prospectively collected by a questionnaire from all psoriasis patients. Patients with joint-related symptoms were assessed by a rheumatologist for the presence of PsA. Retrospectively, the sensitivity and specificity, positive and negative predictive values, likelihood ratios, and posttest probabilities of various screening questions were calculated to identify the best combination of parameters. Of 517 patients seen in dermatology clinic, 117 (22.63 %) were found to have PsA. Four screening questions ("Do you have a history of joint pain or swelling?" "Do you have stiffness in the morning?" "Have you had X-rays taken of your joints?" "Do you have PsA?") with psoriatic nail changes demonstrated high sensitivity and specificity for predicting PsA. A cutoff of three out of these five parameters correctly classified patients with and without PsA with 86.9 % sensitivity, 71.3 % specificity, 53 % positive predictive value (PPV), 93.6 % negative predictive value (NPV), and area under the curve (AUC) of 0.87. Likelihood ratios for individual parameters varied between1.6 and 3.7, and with a combination of certain parameters, the posttest probability of PsA was 76 %. This is a preliminary data on a potential screening questionnaire which can help dermatologists quickly screen for PsA. All patients not having evaluated by a rheumatologist could have led to underdiagnosis of PsA and potential misclassification. Psoriasis patients seen at a specialty clinic may introduce a referral bias.
