EXTENDED REPORT

Are American College of Rheumatology 50% response criteria superior to 20% criteria in distinguishing active aggressive treatment in rheumatoid arthritis clinical trials reported since 1997? A meta-analysis of discriminant capacities

C P Chung¹, J L Thompson^2,5, G G Koch², I Amara³, V Strand⁴, T Pincus¹

¹ Division of Rheumatology and Immunology, Department of Medicine, Vanderbilt University Medical Center, Vanderbilt University, Nashville, Tennessee, USA
² Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
³ Quintiles, Durham, North Carolina
⁴ Stanford University, Portola Valley, California, USA
⁵ Department of Biostatistics, University of North Carolina, Chapel Hill, North Carolina, USA

Correspondence to:
T Pincus
Division of Rheumatology and Immunology, Department of Medicine, Vanderbilt University Medical Center, 203 Oxford House, Box 5, Nashville, TN 37232-4500, USA; t.pincus{at}vanderbilt.edu

Objective: To carry out a meta-analysis designed to compare the discriminant capacities of American College of Rheumatology 50% (ACR50) with 20% (ACR20) responses in clinical trials on rheumatoid arthritis reported after 1997 and to analyse whether ACR50 can be as informative as ACR20 in distinguishing active from control treatments in more recent trials.

Methods: Clinical trials on rheumatoid arthritis reported since 1997 were identified, which included aggressive combinations of disease-modifying antirheumatic drugs and glucocorticoids, as well as powerful new agents—leflunomide, etanercept, infliximab, anakinra, adalimumab, abatacept, tacrolimus and rituximab. A meta-analysis of ACR20 compared with ACR50 responses for 21 clinical trials was carried out on differences in proportions of responders for active and control treatments and corresponding odds ratios (ORs).

Results: In all but one clinical trial on rheumatoid arthritis published since 1997 with data available on ACR20 and ACR50, more than 50% of patients who were ACR20 responders among those randomised to active treatment were also ACR50 responders. This phenomenon was seen for control groups in 38% of trials, many of which included treatment with methotrexate. A meta-analysis of the clinical trials indicated a slight advantage to ACR50 for quantifying treatment comparisons, not significant for differences in proportions but significant for ORs.

Conclusion: ACR20 and ACR50 seem to be similar in distinguishing active from control treatments in clinical trials on rheumatoid arthritis reported since 1997. As ACR50 represents a considerably stronger clinical response, ACR50 may be a preferred end point for contemporary clinical trials on rheumatoid arthritis.

Abbreviations: ACR20, American College of Rheumatology 20% response criteria; ACR50, American College of Rheumatology 50% response criteria; DMARD, disease-modifying antirheumatic drug

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