Do Neutrophil-to-Lymphocyte Ratio and Platelet-to-Lymphocyte Ratio Predict In-Hospital and Long-Term Mortality in Endocarditis Patients?: A Systematic Review and Meta-Analysis

Infective endocarditis (IE) remains a severe condition associated with significant in-hospital and long-term mortality despite advances in antimicrobial therapy and surgical management, highlighting the need for simple and reliable prognostic markers. The neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR), derived from routine complete blood counts, have emerged as accessible inflammatory indices with potential prognostic value in cardiovascular and infectious diseases. We conducted a systematic review and meta-analysis in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to evaluate the ability of admission NLR and PLR to predict mortality in adult patients with IE. A comprehensive search of PubMed, MEDLINE, the Cochrane Library, CINAHL, and Web of Science through May 2024 identified 7 eligible observational studies comprising 847 patients. Random-effects meta-analysis using restricted maximum likelihood estimation with Hartung-Knapp adjustment demonstrated that NLR levels were consistently higher among nonsurvivors than survivors, yielding a pooled standardized mean difference of 1.25 (95% CI -0.13 to 2.63), although statistical significance was not achieved and substantial heterogeneity was observed (I2 = 94.5%). Diagnostic accuracy analysis demonstrated good prognostic performance of NLR for in-hospital mortality, with a pooled area under the curve of 0.85 (95% CI 0.57-1.00; P = 0.002) and no observed heterogeneity. Optimal NLR cutoff values ranged from approximately 5.5 to 9.8 across studies. Evidence regarding PLR was limited and inconsistent, preventing definitive conclusions regarding its prognostic utility. Overall, admission NLR appears to be an inexpensive, reproducible biomarker with good discriminative ability for predicting mortality in IE, although larger prospective multicenter studies are required to validate these findings and clarify the role of PLR in risk stratification.