Association between CALLY index and all-cause mortality in patients with rheumatoid arthritis

Purpose The CALLY index reflects immune, inflammatory, and nutritional status, but its prognostic role in rheumatoid arthritis (RA) remains uncertain. We investigated whether the CALLY index was independently associated with all-cause mortality in patients with RA, and further examined its nonlinear pattern, and consistency across clinical subgroups. Methods We included 5,626 participants with RA from the UK Biobank, with a median follow-up of 15.6 years. Multivariable Cox regression models were used to assess the association between the CALLY index and all-cause mortality. Restricted cubic splines were used to explore potential nonlinearity. Predictive performance was evaluated using time-dependent ROC analysis, IDI, and NRI. Subgroup and sensitivity analyses were performed to test the robustness of the findings. Results A higher CALLY index was independently associated with a lower risk of all-cause mortality in RA patients. This association showed a nonlinear inverse dose–response pattern, with an estimated inflection point of 1.054. The CALLY index showed better reclassification than its individual components and achieved non-inferior predictive performance compared with the combined three-biomarker model. The association was broadly consistent in clinical subgroups and stable in sensitivity analyses. Conclusion The CALLY index may serve as a simple, low-cost biomarker for long-term mortality risk stratification in patients with RA.