Objective: To ascertain how well the disease activity score discriminates drug from placebo treated patients.
Methods: Three placebo controlled trials in rheumatoid arthritis (RA) were reanalyzed using the disease activity score: DAS = 0.53938 x SQRT (Ritchie index) + 0.06465 x (# swollen joints) + 0.330 x 1n (erythrocyte sedimentation rate) + 0.224.
Results: Patient groups receiving methotrexate, high dose D-penicillamine and sulfasalazine had the statistically greatest improvement vs placebo treated groups; patient groups receiving gold sodium thiomalate (GSTM) and low dose D-penicillamine also showed statistically significant improvement versus placebo treated groups. Patients receiving sulfasalazine or GSTM were deemed to benefit compared to placebo treated patients in this analysis, unlike the results presented in the initial analyses of this trial.
Conclusion: The disease activity score is a simple and effective measure of inflammation that can discriminate between active drug and placebo treated patient groups. Use of this composite measure may improve analysis of clinical trials and also be applicable to clinical care.