Baseline ESR–CRP difference (D score) and JAK inhibitor discontinuation for loss of efficacy after biologic failure in rheumatoid arthritis

Abstract Objectives To assess whether baseline ESR–CRP difference (D score) is associated with discontinuation due to loss of efficacy during Janus kinase inhibitor therapy after biologic failure in rheumatoid arthritis. Methods Single-centre retrospective cohort of 24 patients with rheumatoid arthritis who initiated a Janus kinase inhibitor after inadequate response to at least one biologic DMARD. D score was ESR (mm/h) minus CRP (mg/L). The primary outcome was discontinuation due to loss of efficacy; other discontinuations were censored. Kaplan–Meier curves and Cox models were used. Results Seven patients discontinued due to loss of efficacy. After dichotomisation at the median D score (20.3; n = 12 per group), 1-year LOE-free persistence was 90.9% in the high D group and 43.2% in the low D group (log-rank p = 0.004). The hazard ratio per 10-unit increase was 0.47 (95% CI 0.29 to 0.76; p = 0.002) and 0.41 after age adjustment (0.22 to 0.74; p = 0.003). Conclusions Baseline D score was associated with lower risk of discontinuation due to loss of efficacy. Larger studies are needed. Key messages Loss-of-efficacy discontinuation tended to cluster in patients with low ESR and low CRP at baseline. Higher baseline D score was associated with fewer loss-of-efficacy discontinuations during JAK inhibitor therapy. D score from ESR and CRP may complement post-biologic treatment decisions, pending external validation.