Abstract: Objective  To investigate the relationship between prognostic nutritional index (PNI) and treatment failure in patients with peritoneal dialysis-associated peritonitis (PDAP).  Methods  A total of 205 PDAP patients hospitalized in the Department of Nephrology from January 2016 to August 2024 were enrolled. Based on treatment outcomes, patients were divided into a cured group (n=170) and a treatment failure group (n=35). Clinical data were compared between the two groups.  Results  Compared with the cured group, the treatment failure group had longer dialysis vintage (Z=-3.422, P=0.001),  higher peritoneal effluent white blood cell (WBC) count on day 3 (Z=-5.219, P＜0.001),higher levels of C-reactive protein (CRP) (Z=    -3.044, P=0.002) , but lower body mass index (BMI) (Z=-2.032, P=0.042) and PNI (t=6.707, P＜0.001). Univariate logistic regression analysis showed that self-administered antibiotic use before admission (OR =4.592, 95% CI:2.118～9.957, P＜0.001), longer dialysis vintage (OR=1.250, 95% CI:1.105～1.414, P＜0.001), higher day 3 peritoneal effluent WBC count (OR=1.021, 95% CI:1.007～1.035, P=0.003), higher CRP (OR= 1.006, 95% CI:1.002～1.010, P=0.002),  lower BMI (OR =0.886, 95% CI:0.796～0.987, P=0.028), and lower PNI (OR=0.833, 95% CI:0.771～0.898, P＜0.001) were risk factors for treatment failure in PDAP patients. Multivariate logistic regression analysis confirmed that longer dialysis vintage (OR=1.179, 95% CI:1.018～1.363, P=0.027), higher day 3 WBC count (OR=1.028, 95% CI:1.010～1.046, P=0.002), and lower PNI (OR=0.853, 95% CI :0.771～0.937, P=0.001) were independent risk factors for treatment failure. Receiver operating characteristic (ROC) curve analysis showed that PNI had the highest predictive value for treatment failure (AUC=0.776), and its predictive performance further improved when combined with dialysis vintage (AUC=0.816).  Conclusion  PNI reflects the nutritional and immune status of the body and is associated with PDAP treatment failure. It demonstrates good predictive ability for treatment outcomes, and its predictive power increases when combined with dialysis vintage.

Key words: Prognosis nutrition index, Renal dialysis-related peritonitis, Age of dialysis, Albumin, Lymphocyte