The role of NLR and MPV in predicting pressure injury development in ICU patients: a retrospective cohort study

Pressure injuries are a common and serious complication in critically ill patients, yet reliable and accessible biomarkers for early risk stratification remain lacking. This study investigated the predictive value of the neutrophil-to-lymphocyte ratio (NLR) and mean platelet volume (MPV) for pressure injury development in intensive care unit (ICU) patients. This retrospective cohort study included 941 adult patients admitted to the ICU of a tertiary referral centre between January 2022 and January 2025. NLR and MPV were calculated from admission complete blood counts. Pressure injuries were identified and staged by a wound care nurse according to the NPUAP/EPUAP 2019 classification. Univariate and multivariate logistic regression, propensity score matching, competing risk analysis, ROC curve analysis, and Kaplan–Meier survival analysis were performed. Pressure injuries developed in 191 patients (20.3%), with a median onset of 9 days after ICU admission. NLR was significantly higher in patients who developed pressure injuries compared to those who did not (median 8.83 vs. 6.50; p = 0.005), whereas MPV did not differ between groups ( p = 0.355). Propensity score matching confirmed that NLR elevation was explained by confounding from illness severity rather than a direct association with pressure injury development. Neither NLR nor MPV demonstrated clinically meaningful discriminative ability in ROC analysis (AUC 0.566 and 0.522, respectively), and neither emerged as an independent predictor in multivariate analysis. Independent predictors of pressure injury development were ICU length of stay (aOR 1.074; p < 0.001), Braden score (aOR 0.751; p < 0.001), and hemoglobin level (aOR 0.873; p = 0.003). ICU mortality was markedly higher in patients who developed pressure injuries (83.8% vs. 30.7%; OR 11.67, 95% CI 7.71–17.67; p < 0.001). A single admission measurement of NLR or MPV is insufficient to reliably predict pressure injury development in critically ill patients. Propensity score matching indicated that the higher NLR observed in affected patients reflected underlying illness severity rather than an independent association with pressure injury. Among the independent predictors, admission Braden score and hemoglobin level are baseline parameters suitable for early risk stratification, whereas ICU length of stay is a time-dependent variable that accrues during the clinical course and should be interpreted with caution rather than as a baseline predictor. The strong association between pressure injury and ICU mortality is not necessarily causal and more likely reflects shared underlying illness severity; it nonetheless underscores the need for early and sustained preventive strategies in this patient population.