Biologic therapy response and drug survival for females compared to males with rheumatoid arthritis: a cohort study.

Prior research has identified differences between sexes in rheumatoid arthritis (RA) disease characteristics and treatment response, but not how these differences affect therapeutic decision making to switch therapy. Our objective was to assess for sex differences in RA disease activity during the course of biologic therapy and how these differences impact drug survival and therapeutic switching. Data from the Alberta Biologics Pharmacosurveillance Program, a population-based observational cohort of patients receiving biologic therapy for RA, were used for a sex-stratified analysis of disease activity. Linear mixed-model analysis was applied to compare continuous effectiveness outcomes (DAS28, HAQ scores, visual analogue scales of patient-reported outcomes). Chi-squared tests and log-rank tests were used to determine differences in the frequency of switching and drug survival between females and males. At biologic initiation, females (n = 419) and males (n = 148) had similar disease activity (DAS28 in females 5.83, males 5.72), but females reported worse function (HAQ 1.64 vs 1.51, p = 0.037) and more fatigue (6.7 vs 5.9/10, p = 0.013), but the same global score as males (6.9 vs 6.8/10). During biologic therapy, females reported more fatigue (β = -0.454, 95 % CI -0.852, -0.056, p = 0.0252), worse function (β = -0.183, 95 % CI -0.291, -0.074, p = 0.0010) and higher DAS28 scores (β = -0.401, 95 % CI -0.617, -0.184, p = 0.0003). A new composite disease activity index, the HUPI, eliminated the observed differences in disease activity scores between females and males. Median survival for biologic-naïve patients was similar between sexes (3.7 years males, 3.3 years females, log-rank test p = 0.25). The frequency of switching and survival on subsequent biologics were the same between females and males. Guided by traditional outcome measurement tools, worse disease activity and patient-reported outcomes through the course of therapy did not translate into differences in drug survival or more frequent switching for females on biologic therapy for RA.