- Design
- Multicentre registry cohort with trajectory and landmark analysis
- Population
- 843 patients with RA starting JAK inhibitors, Japan
- Primary outcome
- 52-week CDAI trajectory
- Effect
- Favourable-course thresholds: CDAI 12.0 (week 4), 9.3 (week 12); rapid responders 64.9%
A Japanese multicentre registry followed 843 patients with rheumatoid arthritis starting a JAK inhibitor over 52 weeks. Trajectory modelling found four groups: rapid responders (64.9%), partial responders with residual activity (18.1%), responders starting from high activity (12.7%) and persistent non-responders (4.3%). Week-52 remission ranged from 0% to 47.7% across them.
The absolute CDAI at weeks 4 and 12 predicted a favourable trajectory well; the slope of improvement added almost nothing. The best thresholds were CDAI 12.0 at week 4 and 9.3 at week 12.
This turns treat-to-target into a concrete checkpoint: a patient with CDAI above about 9 at week 12 is unlikely to reach a good year on that drug. Thresholds were derived and internally validated in one registry.
- Book a review at week 12 after starting a JAK inhibitor.
- If CDAI is above about 9, plan a switch rather than waiting to 6 months.
- Use week 4 CDAI (above 12) as an early warning.
- Judge response by the level reached, not by how much it has fallen.
Why it matters
It gives a specific time and level at which to stop waiting for a JAK inhibitor to work.
Don't overread it
Registry-derived thresholds from Japanese patients, not yet externally validated.
The statistics, in plain English
The thresholds were chosen to best separate favourable from unfavourable courses in this registry; applied elsewhere they will be less precise. Bootstrap validation showed little over-fitting.
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