Nonlinear Relationship of Leukocyte-to-Albumin Ratio with Disease Activity in Rheumatoid Arthritis

The assessment of disease activity in rheumatoid arthritis (RA) is crucial for clinical management. In recent years, composite inflammatory markers, such as the leukocyte-to-albumin ratio (LAR), have demonstrated prognostic value in various diseases; however, its relevance in RA remains unclear. This study aims to investigate the association between LAR and disease activity in RA, as measured by the DAS28-ESR and DAS28-CRP scores.

This retrospective study enrolled 1070 patients with RA, who were categorized into three groups based on LAR tertiles: T1 (0.06-0.14), T2 (0.14-0.19), and T3 (0.19-0.88). Demographic characteristics, laboratory parameters (including inflammatory markers, complete blood count, and biochemical indicators), and disease activity scores were collected. Univariate analysis, multivariate linear regression, and piecewise linear regression models were employed to evaluate the association between LAR and DAS28 scores, with adjustments for confounding factors such as sex, age, and medication use.

Patients in the high-LAR group (T3) exhibited significantly elevated levels of inflammatory markers (ESR, CRP, and fibrinogen; all P < 0.001) and lower albumin levels (P < 0.001). Univariate analysis revealed a significant positive correlation between LAR and both DAS28-ESR (β = 3.949, P < 0.001) and DAS28-CRP (β = 4.804, P < 0.001). After multivariate adjustment, LAR remained independently associated with DAS28-ESR (β = 1.846, P < 0.001) and DAS28-CRP (β = 2.450, P < 0.001). Piecewise regression analysis identified an inflection point in the LAR-DAS28 relationship at LAR = 0.20. Below this threshold, the association was stronger (DAS28-ESR β = 6.33, P < 0.001), whereas above 0.20, the association was attenuated yet remained significant (β = 2.03, P < 0.001).

LAR is an independent factor associated with disease activity in RA, with a particularly pronounced correlation observed in the lower LAR range. These findings suggest that LAR may serve as a simple and cost-effective auxiliary indicator for clinical assessment of inflammatory status and disease activity in RA.