Abstract

Rheumatoid arthritis (RA) is a chronic autoimmune disease that requires regular disease activity assessment to guide treatment and improve outcomes. Composite inflammatory and nutritional biomarkers are promising adjunctive tools for monitoring disease activity. This comparative study aimed to evaluate the levels of C-reactive protein-to-albumin ratio (CAR), platelet-to-albumin ratio (PAR), and prognostic nutritional index (PNI) in RA patients and healthy controls, and to compare their diagnostic performance and utility for disease activity assessment. The study included 165 RA patients and 167 age- and sex-matched controls. Disease activity of RA was assessed using the Disease Activity Score-28 based on erythrocyte sedimentation rate (DAS28-ESR) and classified into high (DAS28-ESR ˃5.1) and non-high (DAS28-ESR ≤5.1) disease activity groups. Complete blood count, serum albumin, and C-reactive protein (CRP) were measured to calculate CAR, PAR, and PNI. Rheumatoid arthritis patients had higher CAR and PAR, but lower PNI compared with controls (all p<0.001). Patients with high disease activity had higher CAR and PAR, but lower PNI than those with non-high disease activity (p<0.001, p=0.001, p=0.018 respectively). CAR and PAR correlated positively with DAS28-ESR, ESR and CRP, whereas PNI correlated negatively with these inflammatory measures. CAR showed the highest diagnostic performance for identifying RA patients (AUC=0.873), followed by PNI and PAR. CAR showed significantly superior performance, with no significant difference between PAR and PNI. CAR also showed the highest discriminatory performance for high disease activity (AUC=0.676) followed by PAR and PNI, although differences among them were not statistically significant. Higher CAR and PAR, whereas lower PNI were significantly associated with increased odds of high disease activity. Only CAR remained an independent predictor (p=0.005) in multivariate analysis. In conclusion, CAR, PAR, and PNI are available composite biomarkers that provide complementary information regarding inflammatory burden and nutritional status in RA patients, with CAR showing the greatest utility.

Keywords: Rheumatoid arthritis; C-reactive protein-to-albumin ratio; platelet-to-albumin ratio; prognostic nutritional index.

Date received: 14 August 2026; accepted: 03 September 2026

PMID:
0000000