Diagnostic Value of the Neutrophil-Lymphocyte Ratio in Fracture-Related Infections: A Retrospective Analysis.

Abstract

To determine whether the previously established neutrophil-to-lymphocyte ratio (NLR) threshold of 2.45 accurately diagnoses fracture-related infection (FRI). Design: Retrospective diagnostic study. Single Level I trauma center. Included were consecutive adults (≥18 y) who underwent deep-tissue or bone biopsy for suspected FRI between January 1, 2018, and December 31, 2024; excluded were patients with immunosuppressive and oncological disorders or missing laboratory data. Primary outcome was diagnostic accuracy of NLR-reported as sensitivity, specificity, and area under the receiver-operating-characteristic (ROC) curve-for fracture-related-infection. Neutrophil-lymphocyte-ratios of patients with confirmed fracture-related-infection confirmed via bone or deep tissue biopsy were compared with those of patient's with negative (aseptic) biopsies. Per AO/ASIF consensus criteria, biopsy results were considered positive for infection if: (1) phenotypically indistinguishable pathogens were identified by culture from at least two separate deep tissue/implant specimens, or (2) the presence of microorganisms in deep tissue specimens confirmed by histopathological examination. Forty biopsies from 29 patients met inclusion criteria. Of the 40 biopsies, 27 were septic and 13 aseptic. The septic cohort had a mean age of 44 years with a range of 18-64 and consisted of 20 males and 2 females. The aseptic cohort had a mean age of 49 with a range of 27-70 and consisted of 6 males and 1 female. Using the pre-specified NLR threshold of 2.45, sensitivity and specificity for diagnosing fracture-related infection were 92.6% (95% CI 75.7-99.1) and 92.3% (95% CI 64.0-99.8), respectively. Exploratory Receiver operating characteristic analysis suggested an optimal NLR cut-off point of 2.52 for detecting FRI, with an area-under-the-curve of 0.89 (95 % CI 0.74-1.00). Median NLR was significantly higher in septic biopsies, 4.79 (IQR 3.95-8.54), than in aseptic biopsies, 1.78 (IQR 1.50-2.15) (p = 0.003). An NLR > 2.45 occurred in 92.6 % of septic versus 7.7 % of aseptic biopsies (p < 0.001; OR 150, 95 % CI 12.4-1822.3). An NLR threshold of 2.45 provided high sensitivity and specificity for detecting fracture-related infection. These findings support its potential utility as a non-invasive screening tool to detect fracture-related infections. III.