Enthesitis is common in patients with psoriatic arthritis but most patients experience resolution within a year of starting DMARD treatment, regardless of the medications prescribed, a study has found.

Researchers in Canada retrospectively analysed enthesitis data collected from patients attending a PsA clinic who were enrolled in a study to evaluate the effectiveness of conventional disease-modifying antirheumatic drugs (cDMARDs) and targeted DMARD in treating PsA.

Of the 1270 patients in the study, about half had enthesitis, and 526 patients had adequate follow-up data for analysis.

The patients had a mean age 49 years and mean enthesitis score of 2.13 and median enthesitis score 2. They were divided into exclusive groups of either no treatment or NSAIDs only;  cDMARDs (such as methotrexate or leflunomide) with or without NSAIDs; and tDMARDs (predominantly TNF inhibitors) with or without cDMARDs/NSAIDs.

Published in the Journal of Rheumatology, the results showed that the vast majority of patients (86%) had complete resolution of enthesitis within a year of starting treatment for PsA, with resolution seen within a mean period of 8.73 (3.48) months from baseline.

While not statistically significant, there was a trend for patients treated with cDMARDs and tDMARDs to have higher rates for resolution of enthesitis (88.3% and 86.7% respectively) compared to patients who received only NSAIDs or no treatment (82.4%).

The researchers said it was also notable that enthesitis resolution was associated with lower joint activity.

This observation was similar to findings from a registry study that showed patients with enthesitis had worse arthritis and were less likely to achieve minimal disease activity as compared to those without enthesitis, they commented.

But they also noted that there had been few studies of DMARDs  with extensive evaluation of  enthesitis as a major outcome.

“To our knowledge, this is the first study including all sites from the enthesitis indices in a large number of patients with PsA,” they wrote.

The similarity in complete resolution of enthesitis seen across different medication categories was in contrast with the recent PsA treatment recommendations, that are weighed in favour of tDMARDs, authors said.

“In routine clinical practice, therapeutic decisions in patients with PsA are heavily biased toward joint and skin activity, compared to other clinical domains. Though most clinical trials of tDMARDs demonstrate an across-the-board effect for all the clinical domains of PsA, for individual patients the effectiveness may vary between domains as well as in time to response,” they wrote.

However they acknowledged that there are many limitations in the clinical assessment of enthesitis, particularly in differentiating inflammatory from metabolic, mechanical, and degenerative processes.

The development of imaging techniques such as ultrasound and MRI may improve the accuracy of clinical assessment of the actual burden of enthesitis in PsA, they suggested.