The American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR) have defined remission using Boolean- or index-based criteria (i.e., a Simplified Disease Activity Index [SDAI] score of ≤3.3). We undertook this study to compare definitions of remission to inform choice of end points for future rheumatoid arthritis (RA) clinical trials, and we also included in our comparison the remission criterion of a score of ≤2.8 on the Clinical Disease Activity Index (CDAI).
We performed post hoc analyses on clinical remission rates using data from 2 infliximab trials (the ASPIRE [Active-Controlled Study of Patients Receiving Infliximab for the Treatment of Rheumatoid Arthritis of Early Onset] and ATTRACT [Anti-Tumor Necrosis Factor Trial in Rheumatoid Arthritis with Concomitant Therapy] trials) and 1 golimumab trial (the GO-FORWARD trial). We investigated stringency of the different remission definitions, their power to discriminate between active drug and comparator, and aspects of their internal and external validity. We also investigated population determinants of discriminatory power for a particular remission end point.
In patients with early RA (the ASPIRE trial), ACR/EULAR Boolean, CDAI, and SDAI remission rates at 6-7 months were 4-6% for methotrexate (MTX) alone versus 11-14% for infliximab plus MTX. In patients with MTX-refractory active RA (the ATTRACT and GO-FORWARD trials), remission rates were ≤1% for comparator (add-on of placebo) versus 4-6% for add-on of infliximab in the ATTRACT trial and ≤3% for comparator (add-on of placebo) versus 11-13% for add-on of golimumab in the GO-FORWARD trial. Existing remission cut points of different measures were generally comparable, with the Boolean criteria being somewhat more stringent than the SDAI and CDAI criteria. Remission rates were similar across definitions, as was average statistical power (CDAI, 55.6%; Boolean, 59.9%; SDAI, 62.6%).
Remission is an ambitious primary end point for RA clinical trials, to be reserved for selected scenarios based on power considerations. The ACR/EULAR definitions are interchangeable, with slightly higher stringency of Boolean criteria over index-based criteria.