Continuous indices of core data set measures in rheumatoid arthritis clinical trials: lower responses to placebo than seen with categorical responses with the American College of Rheumatology 20% criteria.
OBJECTIVE: To describe indices that are continuous counterparts of categorical responses to the American College of Rheumatology 20% improvement criteria (ACR20), ACR50, and ACR70, which extend rheumatoid arthritis ( RA) clinical trial results and recognize clinical worsening (as well as improvement) with active and placebo treatments. METHODS: Data from a clinical trial of leflunomide, methotrexate, and placebo treatment over 1 year were reanalyzed. Percent change was computed for each of the 7 components of the ACR core set of outcome measures. Four continuous indices were computed: 1) ACR-N (lowest of 3 values: number of swollen joints, number of tender joints, and median of the other 5 measures); 2) composite (median of all 7 measures [3 patient and 3 assessor measures plus erythrocyte sedimentation rate]); 3) patient-only (median of physical function, pain, and global status); and 4) assessor-only (median of number of swollen joints, number of tender joints, and global status). Means, medians, categorical 20%, 50%, and 70% responses, and continuous probability plots were computed according to each index for the 3 treatment groups and were compared with one another and with standard ACR20, ACR50, and ACR70 responses. RESULTS: Mean levels of improvement calculated using the different methods, in patients taking leflunomide, placebo, and methotrexate, respectively, were as follows: ACR-N 20%, -12%, and 13%; composite 43%, 9%, and 33%; patient-only 36%, 0%, and 26%; assessor-only 50%, 20%, and 44%; and ACR20 52%, 26%, and 46%. Differences between leflunomide and placebo were 30-36%, and differences between methotrexate and placebo were 24-26%. CONCLUSION: Continuous indices may be an informative addition to categorical ACR 20%, 50%, or 70% responses to compare efficacies of various treatments in RA, and to describe lower responses to placebo by recognizing worsening as well as improvement.[1]References
- Continuous indices of core data set measures in rheumatoid arthritis clinical trials: lower responses to placebo than seen with categorical responses with the American College of Rheumatology 20% criteria. Pincus, T., Amara, I., Koch, G.G. Arthritis Rheum. (2005) [Pubmed]
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