Table 1_Neutrophil-to-lymphocyte ratio as a harbinger of peritonitis in peritoneal dialysis: a case–control study.docx

BackgroundThe neutrophil-to-lymphocyte ratio (NLR) is a biomarker of systemic inflammation and has been associated with adverse outcomes in dialysis patients. Its role in predicting the future risk of peritoneal dialysis-associated peritonitis (PDAP) before clinical onset remains unclear.
ObjectiveTo evaluate the association between pre-peritonitis NLR levels and the risk of developing PDAP.
MethodsWe conducted a retrospective, matched (1:1) case–control study involving patients on peritoneal dialysis at a single center between January 2010 and October 2024. Cases were patients who developed a first episode of PDAP (diagnosed per ISPD guidelines). Controls were matched to cases on sex and age (±3 years). The exposure was NLR measured from routine blood tests during a 3-month period preceding the peritonitis event for cases, or a corresponding pre-index period for controls. Logistic regression analysis was used to assess the association.
ResultsA total of 178 patients (89 cases and 89 matched controls) were included in the analysis. In conditional logistic regression models accounting for the matched design, a higher NLR was independently associated with an increased risk of PDAP. When analyzed as a continuous variable (per 1-unit increase in ln(NLR)), the fully adjusted odds ratio (OR) was 2.25 (95% confidence interval [CI]: 1.26–4.02, p = 0.006). When NLR was categorized into tertiles, patients in the highest tertile (NLR ≥ 1.24) demonstrated a consistent positive association with peritonitis risk compared to those in the lowest tertile (NLR < 0.52), with a fully adjusted OR of 11.00 (95% CI: 3.06–39.52, p < 0.001; P for trend < 0.001). Restricted cubic spline analysis revealed a significant linear dose–response relationship (P for non-linearity = 0.511). An elevated NLR (≥ median) also showed moderate discriminative ability for predicting PDAP, with an area under the curve (AUC) of 0.78 (95% CI: 0.71–0.85).
ConclusionA higher NLR measured during a clinically stable period prior to infection is associated with an increased risk of subsequent PDAP. If validated in prospective studies, NLR may serve as a simple and readily available biomarker for risk stratification in this population.