The neutrophil percentage-to-albumin ratio predicts mortality in US adults with rheumatoid arthritis: Results from NHANES 2003–2018

The neutrophil percentage-to-albumin ratio (NPAR), calculated from neutrophil percentage and serum albumin levels, has been proposed as an inflammation-related indicator. Despite increasing interest in NPAR as an inflammatory marker, its prognostic relevance in rheumatoid arthritis (RA) remains insufficiently understood. The objective of this study was to investigate the prognostic relevance of NPAR in US adults with RA, particularly regarding all-cause and cardiovascular mortality, and to evaluate the prognostic performance of both NPAR and the neutrophil-to-lymphocyte ratio. Data were obtained from the National Health and Nutrition Examination Survey (NHANES) 2003-2018. RA status was identified according to participants' self-reported physician diagnosis, consistent with previous NHANES investigations. NPAR was calculated as neutrophil percentage × 100/albumin concentration (g/dL). Statistical analyses incorporated the NHANES complex survey framework, including weighting, stratification, and clustering procedures. Missing covariate data were addressed using multiple imputation. Associations between NPAR and mortality outcomes were examined using survey-weighted Cox regression models and restricted cubic spline analyses. The analysis included 2060 adults with RA, among whom 484 died during follow-up and 1576 remained alive. All-cause and cardiovascular mortality risks increased across NPAR levels and remained highest in the top quartile after multivariable adjustment. Kaplan-Meier analysis demonstrated significantly reduced survival probabilities among participants in the highest NPAR quartile, except for those with diabetes. NPAR exhibited a positive linear association with risks of all-cause and cardiovascular death in the restricted cubic spline models. Calculated AUCs reached 0.63 for the former and 0.66 for the latter, suggesting modest discriminatory power akin to neutrophil-to-lymphocyte ratio. NPAR was independently linked to mortality during follow-up in US patients with RA. As a routinely available biomarker, it may have prognostic relevance, although its predictive ability was relatively limited.