Among patients with psoriatic arthritis, a 36-item Short Form Health Survey was the best predictor of progression from oligoarticular to polyarticular arthritis.
Patients with a lower 36-item Short Form Health Survey (SF-36) mental component summary (MCS) were more likely to progress from oligoarticular to polyarticular psoriatic arthritis (PsA), according to a study published in The Journal of Rheumatology.1
“In the past 2 decades, many new medications have been approved for the treatment of PsA. Many of the randomized controlled trials required 5 tender and swollen joints, whereas others required only 3 tender and swollen joints and had an average of 20 tender and 15 swollen joints; in some jurisdictions, patients with oligoarticular disease (< 5 joints) are not able to receive biologic therapy,” investigators explained. “It [was] unclear whether patients with oligoarticular disease differ from those with polyarticular disease and what characteristics predict progression from oligoarticular to polyarticular disease.”
Newly diagnosed (≤ 12 months) patients with 2 or more visits to the University of Toronto PsA clinic between 1978 and 2018 were identified for this analysis. Patients were followed at 6- to 12-month intervals wherein investigators examined laboratory data, patient questionnaires, such as the Health Assessment Questionnaire (HAQ) and SF-36, demographics, and clinical history and examinations, including 68 tender and 66 swollen joint counts. Radiographs were performed every 2 years. Oligoarthritis was recognized as ≤ 4 tender, swollen, or damaged joints. Progression was defined as an increase to 5 or more joints. Logistic and Weibull regression models adjusted for sex, age, and disease duration.
Within this cohort, 47% (n = 192/407) had signs of oligoarthritis and 53% (n = 215/407) were considered to have polyarthritis. While demographics, axial disease, Psoriasis Area Severity Index (PASI) score, medication usage, involved joint distribution, and affected joints were similar to patients with polyarthritis, those with polyarthritis had higher numbers of inflamed joints and were more likely to present dactylitis and enthesitis. The small joints of the hands and feet were most affected in all patients.
Patients with polyarthritis tended to have lower SF-36 scores and higher HAQ scores, indicating reduced function. Within the oligoarticular group, 39% (n = 75) progressed to polyarthritis, with a lower SF-36 score being the main predictor of progression.
“Oligoarticular PsA is similar to polyarticular disease,” investigators concluded. “Lower extremity small joint involvement is associated with polyarticular presentation, but small joint involvement is associated with progression to polyarticular disease.”
Gladman DD, Ye JY, Chandran V, Lee KA, Cook RJ. Oligoarticular vs Polyarticular Psoriatic Arthritis: A Longitudinal Study Showing Similar Characteristics. J Rheumatol. 2021;48(12):1824-1829. doi:10.3899/jrheum.210434