Clinical relevance of C-reactive protein in axial involvement of ankylosing spondylitis

To evaluate C-reactive protein (CRP) as a potential useful criterion of sym ptomatic severity of ankylosing spondylitis (AS), we conducted both a cross sectional and a longitudinal (6 week) clinical study in 443 patients with axial involvement in AS. During the 6 weeks of the study, patients received either a placebo or an active nonsteroidal antiinflammatory drug (NSAID). At baseline, CRP was increased in 173 patients (39%), A multivariate analys is in which CRP was the dependent variable and all clinical assessment crit eria (pain, range of motion, functional disability, hemoglobin, platelet co unt) the independent variables showed that range of motion and laboratory s igns of inflammation were the most significant variables to explain the CRP values. A similar multivariate analysis conducted on the changes in the va riables during the 6 weeks of the study concluded that night pain and labor atory signs of inflammation were the most significant variables explaining the changes in CRP values. The capacity of CRP to discriminate between an a ctive NSAID and a placebo was moderate. This study suggests than an increas e in CRP in patients with AS with axial involvement is not a rare phenomeno n and might be correlated with the clinical severity of the disease. This o utcome measure does not seem to be of great interest in the short term eval uation of fast acting drugs. However, the longterm clinical significance of such an increase in CRP remains to be investigated.