Background Treat-to-target (T2T) is a widely accepted management strategy for rheumatoid arthritis (RA) with a key decision point at 3 months after treatment initiation. At this time point, it remains unclear which patients will benefit from treatment adaptation or from continuation of existing treatment.

Methods We performed a pooled analysis of patient-level clinical trial data of patients with RA. We used a diagnostic testing methodology and a probabilistic approach employing logistic regression to investigate which levels of response at 3 months can inform treatment decisions in regard to achieving the target at 6 months.

Results To be at least 80% sensitive for achieving the low disease activity (LDA) target at 6 months, a change at 3 months in Simplified Disease Activity Index/Clinical Disease Activity Index (SDAI or CDAI) of 58% needs to be observed at 3 months. Higher changes are needed to sensitively predict remission (REM). Not reaching the (minor) SDAI 50% response level is afflicted with very low negative likelihood ratios (LRs) (0.28 for LDA and 0.07 for REM at 6 months). Experiencing (major) SDAI 85% response has substantial positive LRs of 9.2 for reaching LDA and 6.2 for reaching REM at 6 months. In logistic regression, the change at 3 months is significantly associated with reaching of the target at 6 months.

Conclusions The 3-month time point is a critical decision point. Not achieving minor responses at 3 months makes reaching of the treatment target at 6 months highly unlikely, while reaching major responses is highly predictive of reaching the treatment target.