Relative sensitivity to change of the erythrocyte sedimentation rate and serum C-reactive protein concentration in rheumatoid arthritis

OBJECTIVE: To compare the sensitivity to change of the erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) concentration used as measures of rheumatoid arthritis (RA) activity. METHODS: A literature search was conducted to identify all clinical trials and observational studies of disease-modifying medications and corticosteroids in RA that reported results for both ESR and CRP before treatment and 4 weeks to 24 weeks after treatment in the same patients. For each test, effect sizes were computed as the change in the test with treatment divided by the pretreatment standard deviation. A pooled analysis was performed on the paired differences in effect sizes for ESR and CRP within each study. RESULTS: One hundred twenty-three studies with 184 active treatment arms were identified that included measurements of both ESR and CRP. Sixty-three studies with 90 active treatment arms provided sufficient data to permit calculation of effect sizes, and were included in the analysis. In the 36 treatment arms that reported results at 12 weeks, the ESR was more sensitive to change than the CRP, with a paired difference in effect sizes of 0.09 units (95% confidence interval 0.03, 0.15; p = 0.005). In the 76 treatment arms that reported results at 24 weeks, the ESR was also more sensitive to change than the CRP, with a paired difference in effect sizes of 0.11 units (95% CI 0.05, 0.17; p = 0.0004). CONCLUSION: In these studies of disease-modifying medications in RA, the ESR was more sensitive to change than the CRP at 12 weeks and 24 weeks of treatment. Few studies examined changes in these measures at times earlier than 12 weeks.