Serum cotinine as a biomarker of tobacco exposure and the association with treatment response in early rheumatoid arthritis

Abstract

Objective: Cigarette smoking has emerged as a risk factor for the development of rheumatoid arthritis (RA). Recent studies have suggested that cigarette smoking may lead to lower treatment response rates with methotrexate (MTX) and some biologic agents in RA. Knowledge of whether tobacco exposure reduces treatment efficacy is important, since smoking could represent a modifiable factor in optimizing RA treatment.

Methods: The study participants included patients with early RA (<3 years in duration) enrolled in the Treatment of Early Aggressive Rheumatoid Arthritis study, a randomized, blinded, placebo-controlled clinical trial comparing early intensive therapy (MTX + etanercept or MTX + hydroxychloroquine + sulfasalazine triple therapy) versus initial treatment with MTX with step-up to MTX + etanercept or to triple therapy if the disease was still active at 24 weeks. Serum cotinine was measured using a commercially available enzyme-linked immunosorbent assay at baseline and at 48 weeks, with detectable concentrations at both visits serving as an indicator of smoking status. The mean Disease Activity Score in 28 joints (DAS28) was compared by smoking status, adjusting for baseline disease activity.

Results: Of the 412 subjects included in the analysis, 293 (71%) were categorized as nonsmokers and 119 (29%) as current smokers. There were no differences in the mean DAS28 score between 48 and 102 weeks based on smoking status for the overall group (P = 0.881) or by specific treatment assignment.

Conclusion: Among patients enrolled in a large randomized controlled trial of early RA with poor prognostic factors, smoking status did not impact treatment responses for those receiving early combination or initial MTX with step-up therapy at 24 weeks if the disease was still active.

Trial registration: ClinicalTrials.gov NCT00259610.

Figure 1

Disposition of Participants.

Figure 2

Mean DAS-28 over time based on smoking status for each treatment group. A. Etanercept + MTX, both immediate and step-up. B. Triple therapy, both immediate and step-up. C. Initial MTX monotherapy with step-up to triple therapy or MTX + ETN D. Immediate combination therapy.