# Neutrophil-to-apolipoprotein A1 ratio as a novel biomarker for prognosis in anti-NMDAR encephalitis: a retrospective cohort analysis

## TL;DR

This study shows that the neutrophil-to-apolipoprotein A1 ratio (NAR) can predict disease severity and relapse risk in anti-NMDAR encephalitis patients.

## Contribution

NAR is introduced as a novel, independent biomarker for prognosis and recurrence in anti-NMDAR encephalitis.

## Key findings

- High NAR is associated with worse long-term outcomes and higher recurrence rates in anti-NMDAR encephalitis patients.
- NAR independently predicts poor prognosis with 92.2% specificity and an AUC of 0.724.
- Disease severity partially mediates the relationship between NAR and prognosis.

## Abstract

To investigate the correlation between the neutrophil-to-apolipoprotein A1 ratio (NAR) and disease severity, long-term prognosis, and risk of relapse in patients with anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis.

This study included 125 patients with anti-NMDAR encephalitis as a retrospective cohort. Baseline clinical, laboratory, and imaging data was collected. Spearman’s correlation analysis was used to evaluate correlations between NAR, disease severity, and C-reactive protein (CRP) levels. Logistic regression and Cox proportional hazards models were used to analyze independent associations between NAR and poor prognosis and recurrence, respectively. The predictive performance of NAR was evaluated using receiver operating characteristic (ROC) curves. Mediation analysis was used to explore potential pathways of action. Sensitivity and subgroup analyses were performed to verify the reliability of the results.

The final modified Rankin’s score (mRS) score and recurrence rate were significantly higher in the high-NAR group than in the low-NAR group (both p < 0.05). NAR significantly and positively correlated with the initial mRS score (r = 0.308, p < 0.001) and CRP level (r = 0.486, p < 0.001). Multivariate analysis showed that NAR was an independent risk factor for poor prognosis (OR = 1.19, 95% confidence interval (CI): 1.02–1.38, p = 0.026) and recurrence (Hazard ratio (HR) = 1.13, 95% CI: 1.02–1.24, p = 0.017). ROC curve analysis showed that the area under the curve (AUC) for predicting poor prognosis with NAR was 0.724, the optimal cutoff value was 10.34, and the specificity was 92.2%. Mediation analysis showed that disease severity partially mediated the relationship between NAR and prognosis (effect rate, 41.7%).

NAR is an independent predictor of poor disease prognosis and risk of recurrence in patients with anti-NMDAR encephalitis. Its high specificity helps identify high-risk patients early and accurately, giving this biomarker long-term prognostic value.