Testing different thresholds for patient global assessment in defining remission for rheumatoid arthritis: are the current ACR/EULAR Boolean criteria optimal?

Objectives This study aimed to evaluate different patient global assessment (PGA) cut-offs required in the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) Boolean remission definition for their utility in rheumatoid arthritis (RA). Methods We used data from six randomised controlled trials in early and established RA. We increased the threshold for the 0-10 score for PGA gradually from 1 to 3 in steps of 0.5 (Boolean1.5 to Boolean3.0) and omitted PGA completely (BooleanX) at 6 and 12 months. Agreement with the index-based (Simplified Disease Activity Index (SDAI)) remission definition was analysed using kappa, recursive partitioning (classification and regression tree (CART)) and receiver operating characteristics. The impact of achieving each definition on functional and radiographic outcomes after 1 year was explored. Results Data from 1680 patients with early RA and 920 patients with established RA were included. The proportion of patients achieving Boolean remission increased with higher thresholds for PGA from 12.4% to 19.7% in early and 5.9% to 12.3% in established RA at 6 months. Best agreement with SDAI remission occurred at PGA cut-offs of 1.5 and 2.0, while agreement decreased with higher PGA (CART: optimal agreement at PGA <= 1.6 cm; sensitivity of PGA <= 1.5 95%). Changing PGA thresholds at 6 months did not affect radiographic progression at 12 months (mean Delta smTSS for Boolean, 1.5, 2.0, 2.5, 3.0, BooleanX: 0.35 +/- 5.4, 0.38 +/- 5.14, 0.41 +/- 5.1, 0.37 +/- 4.9, 0.34 +/- 4.9, 0.27 +/- 4.7). However, the proportion attaining HAQ <= 0.5 was 90.2%, 87.9%, 85.2%, 81.1%, 80.7% and 73.1% for the respective Boolean definitions. Conclusion Increasing the PGA cut-off to 1.5 cm would provide high consistency between Boolean with the index-based remission; the integer cut-off of 2.0 cm performed similarly.