The Use of Rheumatic Disease Comorbidity Index for Predicting Clinical Response and Retention Rate in a Cohort of Rheumatoid Arthritis Patients Receiving Tumor Necrosis Factor Alpha Inhibitors

Introduction. To retrospectively evaluate the impact of comorbidities on treatment choice, 12-month clinical response, and 24-month retention rate in a cohort of patients with rheumatoid arthritis (RA) treated with a first-line tumor necrosis factor alpha inhibitor (TNFi), by using for the first time the Rheumatic Disease Comorbidity Index (RDCI). Methods. The study population was extracted from a local registry of RA patients receiving adalimumab or etanercept as first-line biologics between January 2001 and December 2013. The prevalence of comorbidities was computed, and patients were stratified according to RDCI for evaluating the role of comorbidities on TNFi choice, concomitant methotrexate, clinical response (1-year DAS28-ESR remission and low disease activity [LDA] and EULAR good-moderate response), and the 24-month retention rate. Results. 346 patients (172 adalimumab and 174 etanercept) were included. A significantly higher EULAR good/moderate response (P = 0.020) and DAS28-ESR remission (P = 0.003) were obtained according to RDCI (0, 1, 2, or 3). Lower RDCI (P = 0.022), male sex (P = 0.006), higher baseline DAS28-ESR (P = 0.001), ETN (P < 0.001), and concomitant methotrexate (P = 0.016) were predictors of EULAR good/moderate response. Elevated RDCI was a predictor of discontinuation of biologics (P = 0.036), whereas treatment with etanercept (P < 0.001) and methotrexate (P = 0.007) was associated with a lower risk of TNFi withdrawal. Conclusions. Multimorbidity, measured by RDCI, is a negative predictor of TNFi persistence on treatment and of achieving a good clinical response. The use of RDCI may be very useful for identifying patients with RA carrying those comorbid conditions associated with poor prognostic outcomes and for defining new treatment targets in multimorbid RA patients.