Comorbid fibromyalgia impairs the effectiveness of biologic drugs in patients with psoriatic arthritis

OBJECTIVES: To evaluate the impact of FM on the clinical outcomes of biologics in patients with PsA in real life. METHODS: FM was diagnosed according to current criteria among PsA patients starting a first biologic drug from 2010 through 2017. At each visit, disease activity of PsA (DAPSA), minimal disease activity (MDA), HAQ, rate of patients achieving DAPSA-based low disease activity (LDA) or remission, and MDA were evaluated. Lost patients or those not achieving the target were imputed as non-responders. The drug survival was evaluated by Kaplan-Meyer analysis. Estimated hazard ratios (HRs) of discontinuing therapy or achieving MDA were assessed by multivariate regression models. RESULTS: A total of 238 patients, of whom 58 had also FM, started a first biologic drug. Compared with no-FM PsA, FM PsA patients were more frequently female (P = 0.0001) with polyarticular subset (P = 0.0001), and with higher mean BMI (P = 0.006). Drug survival was significantly lower in FM PsA (50%, mean 32 months) than in no-FM PsA (74%, mean 42 months, P = 0.0001). Rates of remission/LDA and MDA were significantly lower in FM PsA at 3, 6, 12 and 24 months (P < 0.001). Remission in FM PsA was negligible (3.4% and 0% at 3 and 6 months, respectively). Negative predictors of drug discontinuation were no FM (HR 0.51) and normal weight (HR 0.29), while no FM (HR 2.54) and male sex (HR 1.58) were positive predictors of long-standing MDA. CONCLUSIONS: Comorbid FM, along with female gender and obesity seem to be the worst combination of negative prognostic factors in PsA.