Prevalence of Psoriatic Arthritis among Patients with Psoriasis Using the Psoriatic Arthritis Screening Tool (PEST) Questionnaire in a Tertiary Government Institution

Background. Psoriatic arthritis (PsA) is a complex musculoskeletal disorder that is associated with psoriasis. Its estimated prevalence among patients with psoriasis ranges widely from 6% to 42% in Europe, North America, and South Africa. However, there is a paucity of data in Asia. To date, there is no local study done in the Philippines.

Objective. This study aimed to determine the prevalence of psoriatic arthritis (PsA) among patients with psoriasis in a tertiary institution.

Methods. This is a descriptive cross-sectional study that included 150 patients with psoriasis in the Dermatology Clinic. Demographic and clinical data were collected. Psoriatic Arthritis Screening Tool (PEST) was applied to all participants. Those who scored ≥3 on the PEST were seen at the Rheumatology Clinic and confirmed with the Classification of Psoriatic Arthritis (CASPAR) Criteria. Descriptive statistics were used to describe the demographic and clinical characteristics. The prevalence of psoriatic arthritis among patients with psoriasis was calculated as the percentage of the population who scored ≥3 on the CASPAR Criteria.

Results. Out of the 150 patients with psoriasis, a total of 50 scored ≥3 on PEST. Of these, 47 patients (31.3%) qualified for the diagnosis of PsA using the CASPAR criteria. Thirty-seven out of the forty-seven patients (79%) are known PsA patients, while the remaining 10 patients (21%) were newly diagnosed with PsA. A total of 34 patients (72%) were female, with a mean age of 33 and 39 years at the onset of psoriasis and PsA, respectively. Family history of psoriasis was present in 22 patients (47%). The most common pattern of arthritis was polyarticular (51%) followed by oligoarticular (38%) and axial (11%). Morning stiffness was present in 83% of the patients. Dactylitis was recorded in 16 patients (34%), while 19 patients (40%) had enthesopathy. Onycholysis was the most common nail abnormality seen in 20 patients (43%). Only 13 patients had rheumatoid factor at baseline, and all were negative. Most of the patients did not have imaging studies at baseline.

Conclusion. In this single center study, the diagnosis of psoriatic arthritis among patients who were previously diagnosed with psoriasis increased from 24.5% to 31.3% using PEST as a screening tool, showing its usefulness in improving clinical detection of psoriatic arthritis among these patients.