Abstract
Heart failure (HF) remains a global health challenge with high morbidity and mortality, necessitating reliable biomarkers for risk stratification. The platelet-to-lymphocyte ratio (PLR), an emerging inflammatory marker, has shown prognostic potential in cardiovascular diseases, but its utility in HF remains inconsistently reported. This systematic review synthesizes evidence on PLR's prognostic value in HF, focusing on mortality, hospitalization, and its role in multimarker models. We searched four databases -PubMed, Scopus, Web of Science, and Cochrane Library - for English-language observational studies published between January 2020 and June 2025, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Fourteen studies (n=14) were included after screening 172 records. Inclusion criteria comprised adult HF patients with PLR assessed as a prognostic factor; exclusions included reviews, editorials, abstracts without full data, animal studies, and non-English publications. Data on study characteristics, PLR cut-offs, outcomes, effect estimates, and adjustment covariates were extracted. Risk of bias was assessed using the Newcastle-Ottawa Scale. A meta-analysis was not performed due to high heterogeneity in study design, PLR measurement methods, and outcome definitions. Heterogeneity was further evaluated narratively based on methodological inconsistencies, differences in population characteristics, and statistical adjustments. Elevated PLR was significantly associated with increased mortality in ICU and acute HF settings, particularly when combined with the neutrophil-to-lymphocyte ratio (NLR), suggesting additive prognostic value in multimarker models. In contrast, PLR showed limited predictive utility in stable or community-dwelling HF cohorts. Risk of bias findings influenced interpretation, with stronger associations observed in studies with low bias scores. PLR cut-off thresholds varied substantially across studies, affecting comparability. While PLR adds incremental value in acute settings, especially when integrated with other inflammatory markers, its standalone use in chronic HF remains uncertain. Standardization of PLR measurement and further prospective research are essential to clarify its pathophysiological role and clinical applicability.