Postoperative Day-28 Neutrophil-to-Lymphocyte Ratio as a Predictor of Early Mortality After Lung Transplantation

Background/Objectives: Neutrophil-to-lymphocyte ratio (NLR) may predict outcomes after organ transplantation. This study evaluated the peri-transplant prognostic value of NLR in lung transplantation (LTx). Methods: This retrospective study included 282 LTx recipients (2012-2020). NLR measured on PODs 1, 3, 7, and 28 predicted 6-month mortality. Generalized estimating equations analyzed serial trends. Multivariable regression and ROC analysis identified predictors for a composite model, assessing discrimination and calibration. Results: Among 282 recipients (mean age, 54.2 years; male, 65.2%; idiopathic pulmonary fibrosis, 54.3%), 24.1% died within 6 months, most commonly from infection. Median NLR increased sharply after LTx (pre-LTx, 5.4; POD 1, 23.1; POD 3, 31.2), then decreased (POD 7, 18.8; POD 28, 8.7). Non-survivors had significantly higher preoperative and postoperative NLRs, particularly on POD 28. POD 28 NLR independently predicted 6-month mortality (multivariable analysis: OR, 1.05 per unit; 95% CI, 1.02-1.07; p < 0.001), alongside age and donor lung PaO₂/FiO₂ (P/F) ratio. Notably, a composite model combining these variables demonstrated significantly superior discrimination (area under the curve [AUC], 0.742; p = 0.001) compared to the NLR-only model (AUC, 0.698; p < 0.05). GEE demonstrated significantly steeper post-transplant NLR decline among survivors than non-survivors after adjusting for age (p = 0.02). Patients with NLR > 9.20 at POD 28 (area under the curve, 0.698; 95% CI, 0.615-0.782; sensitivity, 71.4%; specificity, 59.8%)-showed significantly lower survival on Kaplan-Meier analysis (p < 0.001, log-rank). Conclusions: Persistent NLR elevation on POD 28 independently predicts early mortality post-LTx and may support routine post-transplant risk stratification.