The relationship between the C‐reactive protein (CRP)‐albumin‐lymphocyte (CALLY) index and disease activity of rheumatoid arthritis (RA) has not been explored at present. This study included 1058 RA patients and used a multiple linear regression model to evaluate the association between the CALLY index and 28 joint disease activity scores (DAS28) and further explored its potential nonlinear relationship using a two‐stage segmented linear regression model. Multivariate adjusted analysis showed that CALLY was significantly negatively correlated with DAS28‐erythrocyte sedimentation rate (ESR) ( β = −0.119, 95% confidence interval CI: −0.145 to −0.093) and DAS28‐CRP ( β = −0.201, 95% CI: −0.226 to −0.177) (both p < 0.001), and there was a dose–response relationship (trend p < 0.001). Segmented regression analysis revealed a significant nonlinear correlation between the two, with inflection points of 0.499 and 0.555, respectively. Below the inflection point, CALLY has a significant negative impact on disease activity (DAS28‐ESR: β = −2.102, 95% CI: −2.498 to −1.706); DAS28‐CRP: β = −2.311, 95% CI: −2.591 to −2.031); after exceeding the inflection point, this negative correlation effect significantly weakens but still maintains statistical significance. The results of this study indicate a significant nonlinear relationship between the CALLY index and the DAS28 score, especially at low CALLY levels. This study suggests the potential of CALLY as a novel composite biomarker reflecting the inflammatory status and disease severity of RA.
Leng et al. (Thu,) studied this question.