C-reactive protein predicts tumor necrosis factor-alpha blocker retention rate in axial ankylosing spondylitis.

Abstract

In ankylosing spondylitis (AS), tumor necrosis factor (TNF) blockers are recommended for patients with high symptomatic disease activity. Few data are available about objective signs of inflammation such as increased C-reactive protein (CRP). We assessed the retention rate of TNF blockers in patients with axial AS, according to baseline CRP and other potentially predictive measures. A retrospective study of all patients treated with TNF blockers for axial AS. Retention rate was evaluated using a survival-data analysis technique with discontinuation of the drug because of inefficacy (Kaplan-Meier method). Potential factors explaining the retention rates (demographic and clinical indicators and CRP) were evaluated using log-rank tests and a Cox proportional-hazards regression model. For axial AS, 175 patients received TNF blockers (men 78%, mean disease duration 12.4 +/- 9.1 yrs); 100 patients (of 143 with available data) had an increased CRP (> 10 mg/l). An increased CRP at baseline was the only variable explaining the retention rate in the Cox model (p = 0.003, hazard ratio = 3.3, 95% CI 1.5-7.3). Interruption for expert opinion of inefficacy was more frequent for patients with low baseline CRP; however, even in these patients retention was high. Increased CRP should not be considered mandatory for proposing TNF blocker treatment in axial AS.