Association between tumor necrosis factor inhibitor therapy and changes in C-reactive protein among patients with psoriasis, psoriatic arthritis, or rheumatoid arthritis
Objective: To assess changes in C-reactive protein (CRP) for patients with PsO, PsA, or RA exposed to a TNFi with concomitant exposure to methotrexate (MTX) compared to patients exposed to methotrexate therapy with no TNFi.
Methods: This was a retrospective cohort study from data extracted from the electronic databases of the Kaiser Permanente Southern California (KPSC) Health Plan from January 1, 2002 to July 31, 2011. Patients had at least 3 ICD-9 diagnosis codes of PsO (696.1), PsA (696.0), or RA (714, 714.0, 714.1, 714.2, 714.4, 714.81) during the study period but prior to the index date. Among the underlying cohort of patients exposed to MTX, those who initiated a TNFi (adalimumab, etanercept, infliximab, or golimumab) anytime during the study period comprised the TNFi+MTX cohort. The study protocol was approved by the local institutional review board.
Results: There were 979 and 294 patients in the MTX and TNFi+MTX cohorts, respectively. The mean crude change was 1.1?mg/dl (SD=19.84) for the MTX cohort and ?9.2?mg/dl (SD=26.64) for the TNFi+MTX cohort. In the main effects ANCOVA model, there was a significantly lower difference in the mean change of ?5.18?mg/dl (95% CI: ?8.24,?2.12) for the TNFi+MTX cohort compared to the MTX cohort after adjusting for baseline CRP, age, gender, type 2 diabetes, and inflammatory condition.
Conclusions: The use of TNF inhibitors with concomitant MTX was associated with a clinically and statistically significant decrease in CRP in patients with PsO, PsA, or RA.