# Role of Neutrophil-to-Lymphocyte Ratio and Platelet-to-Lymphocyte Ratio in Predicting In-Hospital Mortality in Patients With Diabetic Foot Ulcers Undergoing Amputation: A Retrospective Study

## TL;DR

This study finds that blood cell ratios can predict death risk in diabetic patients undergoing foot amputation, helping doctors manage care better.

## Contribution

The study identifies NLR and PLR as novel independent predictors of in-hospital mortality in diabetic foot ulcer patients undergoing amputation.

## Key findings

- NLR with a cut-off of 9.1 predicted mortality with high sensitivity and specificity.
- High NLR and PLR independently predicted in-hospital mortality in multivariate analysis.
- Common pathogens included Enterococcus spp., E. coli, and Pseudomonas aeruginosa, with antibiotic susceptibility patterns identified.

## Abstract

Background: Diabetic foot ulcers (DFUs) are a severe complication of diabetes and a major cause of non-traumatic lower limb amputations worldwide. Patients undergoing major lower limb amputations (MLLAs) for DFUs often have poor prognoses, with high in-hospital mortality rates. Inflammatory biomarkers, such as the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR), have emerged as potential prognostic indicators in various clinical settings; however, their predictive value in this high-risk population remains underexplored.

Methodology: This retrospective observational study was conducted at a tertiary care center in South India and included all adult patients with diabetes and DFUs who underwent MLLA between January 2019 and December 2022. Data were extracted from a prospectively maintained database. Postoperative NLR and PLR were calculated from the first postoperative day blood counts. Receiver operating characteristic (ROC) curve analysis determined optimal cut-off values for predicting in-hospital mortality. Variables significant on univariate analysis were entered into a multivariate Cox regression model to identify independent predictors of survival. Microbiological culture and antibiotic sensitivity data from ulcer specimens were also analyzed.

Results: Of the 285 patients (mean age, 55.95 ± 10.42 years), 202 (71%) were male, and 47 (16%) died during hospitalization. ROC analysis revealed that NLR had an area under the curve (AUC) of 0.80, with an optimal cut-off point of 9.1 (sensitivity, 89.4%; specificity, 75.6%). In comparison, PLR had an AUC of 0.686 with a cut-off of 302.8 (sensitivity, 68.1%; specificity, 60.1%). On multivariate Cox regression, recently diagnosed diabetes mellitus (HR = 58.009, p=0.001), high NLR (HR = 12.07; p < 0.001), and high PLR (HR = 2.13; p = 0.012) independently predicted in-hospital mortality. Microbiological analysis yielded a total of 926 organisms isolated from 285 patients. The most common pathogens were Enterococcus spp. (21%, n = 194), Escherichia coli (18%, n = 170), and Pseudomonas aeruginosa (17%, n = 155). Enterococcus spp. were most often susceptible to ampicillin, linezolid, and vancomycin.

Conclusion: Elevated postoperative NLR and PLR are independent predictors of in-hospital mortality in DFU patients undergoing MLLA. These readily available biomarkers can assist in early risk stratification and guide postoperative management. The study also provides region-specific data on microbial prevalence and antibiotic susceptibility, supporting more targeted empiric therapy in this high-risk population.