Do Neutrophil-to-Lymphocyte Ratio and Platelet-to-Lymphocyte Ratio Reflect Coronary Artery Disease Severity Assessed by SYNTAX Score?: A Meta-Analysis

Coronary artery disease is a major global cause of morbidity and mortality, with systemic inflammation playing a central role in its pathophysiology. The SYNTAX (Synergy Between percutaneous coronary intervention With Taxus and Cardiac Surgery) score is widely used to quantify the anatomical complexity of coronary lesions, but its invasiveness and cost limit routine application. Hematologic inflammatory indices such as the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) have been proposed as simple, inexpensive biomarkers that may reflect the presence and severity of coronary disease. This meta-analysis evaluated the association between NLR and PLR and angiographic complexity measured by the SYNTAX score. A systematic search of PubMed, MEDLINE, Cochrane, and CINAHL through May 2024 identified studies reporting correlations between NLR and/or PLR and SYNTAX scores in adults with coronary artery disease. Random-effects models using Fisher's z-transformation were applied to pool correlation coefficients. Heterogeneity was assessed using Cochran's Q, I2, and τ2. Subgroup analyses examined the effects of country, study design, and publication year, and meta-regression explored the influence of mean age and sex distribution. Publication bias was evaluated with funnel plots and Egger's regression. Fifteen studies involving 17,348 participants were included. NLR showed a significant positive correlation with SYNTAX score (r = 0.37; 95% CI, 0.28-0.45). PLR demonstrated a similar association (r = 0.38; 95% CI, 0.23-0.51). Heterogeneity was substantial for both indices. Stronger correlations were observed in Turkish cohorts, and increasing mean age was associated with larger effect sizes. No significant publication bias was detected. Both NLR and PLR correlate moderately with coronary lesion complexity and may provide accessible adjunctive markers for preprocedural risk stratification.