White Blood Cell Count as a Prognostic and Mechanistic Mediator in Acute Diquat Poisoning: A Retrospective Cohort Study Enabling Risk Stratification for Resource-Limited Settings

Background Diquat poisoning is associated with high mortality, and accurate prognostication remains challenging in resource-limited settings. This retrospective cohort study evaluated white blood cell count (WBC) as both a prognostic biomarker and mechanistic mediator in acute diquat poisoning. Methods This retrospective cohort included 134 patients with acute diquat poisoning (2016–2025). WBC was analyzed continuously and categorically (median and ROC-derived cut-offs). Multivariable regression, subgroup, and mediation analyses were performed. Results The high-WBC group (≥ 17.11 × 109/L) had significantly higher mortality (64.3% vs. 7.8%, P < 0.001). After adjustment, patients with WBC ≥ 17.235 × 109/L had a 3.43-fold higher mortality risk (95%CI:1.37 – 8.60). Each 1 × 109/L WBC increase predicted a 6% mortality risk rise (adjusted OR = 1.06, 95%CI:1.01 – 1.12). WBC mediated 15.5% (P = 0.02) of plasma diquat's total lethal effect. ROC analysis showed WBC had an AUC of 0.724 (95%CI:63.5% – 81.2%) at the optimal cut-off of 17.235 × 109/L, comparable to plasma diquat concentration's AUC of 0.817 (95%CI:74.4% – 88.9%). Conclusions WBC serves as both a continuous predictor and triage tool at 17.235 × 109/L, providing a practical risk-stratification framework for settings lacking toxicological testing. This study identifies leukocytosis (using the ROC-optimized cut-off value of WBC ≥ 17.235 × 109/L) as a practical triage tool for acute diquat poisoning in settings lacking toxicological testing. The validated cut-off: 1.Identifies high-risk patients with a 3.43-fold increased mortality risk (fully adjusted model) 2.Shows comparable prognostic performance to plasma diquat concentration (AUC = 0.724 vs. 0.817, P = 0.055) 3.Serves as both a continuous and categorical predictor: each 1 × 109/L increase in WBC corresponds to a 6% rise in mortality risk (adjusted OR = 1.06, 95%CI: 1.01 – 1.12). Furthermore, WBC mediates 15.5% of diquat’s lethal effect, providing not only prognostic utility but also insight into underlying inflammatory mechanisms, highlighting its dual role as a biomarker and a potential therapeutic target.