Diagnostic Utility of the Neutrophil-to-Serum Bicarbonate Ratio for Early Recognition of Complicated Urinary Tract Infection in Adults with Diabetes Mellitus
Neutrophil-to-Bicarbonate Ratio in Diabetic Complicated UTI
DOI:
https://doi.org/10.69750/dmls.03.07.0218Keywords:
Bicarbonates, Diabetes Mellitus, Neutrophils, Pyelonephritis, Sensitivity and Specificity, Urinary Tract InfectionsAbstract
Background: Complicated urinary tract infection (UTI) in adults with diabetes may progress to pyelonephritis, bacteraemia, urinary obstruction, sepsis, or renal injury. Early identification using routine laboratory parameters may improve risk stratification.
Objective: To evaluate the diagnostic utility of the neutrophil-to-serum bicarbonate ratio (NSBR) for identifying complicated UTI in adults with type 2 diabetes mellitus.
Methods: This single-centre prospective diagnostic-accuracy study included 80 adults with type 2 diabetes and culture-confirmed symptomatic UTI presenting to Frimley Health NHS Foundation Trust, Slough, Berkshire, United Kingdom, from August 2024 to October 2025. Participants were classified as having localised or complicated UTI using predefined clinical, microbiological, biochemical, and, where indicated, radiological criteria. NSBR was calculated by dividing the absolute neutrophil count by serum bicarbonate. Receiver operating characteristic analysis and multivariable logistic regression were performed.
Results: Complicated UTI was identified in 34 patients (42.5%); 46 (57.5%) had localised UTI. Mean NSBR was higher in complicated cases (0.47 ± 0.12 vs 0.30 ± 0.09; p<0.001). The area under the curve was 0.861 (95% confidence interval [CI], 0.769–0.929). At the data-derived cutoff of ≥0.39, sensitivity was 82.4% (95% CI, 66.5–91.7), specificity 80.4% (66.8–89.3), positive predictive value 75.7% (59.9–86.6), negative predictive value 86.0% (72.7–93.4), and accuracy 81.3% (71.3–88.3). Each 0.10-unit increase in NSBR was independently associated with higher odds of complicated UTI (adjusted odds ratio, 3.41; 95% CI, 1.93–6.03).
Conclusion: NSBR showed good diagnostic discrimination in this single-centre UK cohort and may support initial risk stratification. The proposed cutoff requires external validation before routine clinical use.
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