Understanding difficult-to-treat psoriatic arthritis: Data from the Rheumatic Diseases Portuguese Registry

To estimate the proportion and identify predictors of difficult-to-treat (D2T) psoriatic arthritis (PsA).

A multicentre observational retrospective study was conducted with patients registered in the Rheumatic Diseases Portuguese Registry (Reuma.pt). Two different definitions were used to classify D2T PsA. The first criterion (treatment failure) is defined by the failure of≥2 b/tsDMARDs (first definition) or≥3 b/tsDMARDs (second definition), both with different MoAs; and the second criterion is defined by the presence of signs suggestive of active/progressive disease.

In total, 1873 patients were included, of whom 3.7% (n=70) were classified as having D2T PsA according to the first definition and 0.9% (n=17) as having D2T PsA according to the second definition. D2T PsA was associated with a younger age at symptom onset (37.5±11.0 vs. 41.4±12.8; P<0.01) and at diagnosis (40.7±10.5 vs. 44.7±12.3; P<0.01), polyarticular phenotype (77.6% vs. 53.6%; P<0.001), depression (10.9% vs. 5%; P<0.05), and enthesitis (47.1% vs. 33.5%; P<0.05) and lower body mass index (26.5[6.1] vs. 27.7[6.1]; P<0.01). D2T PsA patients presented with higher tender (13.4[14.5] vs. 6[8]; P<0.001) and swollen joint counts (9[9] vs. 4[6]; P<0.001) and higher DAPSA (38.2[31.6] vs. 25.4[15.6]; P<0.001) at baseline. Polyarticular disease (OR: 3.09), increased baseline swollen joint count (OR: 1.12), and treatment duration on the first b/tsDMARDs (P<0.01) were predictors of D2T PsA.

D2T PsA proportions varied between 0.9% and 3.7%. D2T PsA patients had higher disease activity scores before the initiation of their first b/tsDMARDs and higher rates of treatment discontinuation.