Objective: 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.
Methods: 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.
Results: 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).
Conclusion: 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.