Neutrophil-to-lymphocyte ratio in amyotrophic lateral sclerosis: a systematic review and meta-analysis.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with limited diagnostic and prognostic biomarkers. The neutrophil-to-lymphocyte ratio (NLR), a marker of systemic inflammation, has been proposed as a potential indicator. This systematic review and meta-analysis assesses the diagnostic and prognostic value of NLR in ALS. We searched PubMed, Scopus, Embase and Web of Science through June 2025 for peer-reviewed studies evaluating NLR in adults with ALS diagnosed by established criteria. Eligible studies reported validated measurements of NLR and diagnostic or prognostic outcomes. Two reviewers independently extracted data and assessed quality. Random-effects meta-analyses were performed, with heterogeneity, publication bias, evidence certainty and sources of heterogeneity evaluated using meta-regression. Sixteen studies from 12 countries including 357 044 participants met inclusion criteria, comprising 8710 ALS patients (mean age 60.3 years; 59.1% male) and 348 334 controls (mean age 57.8 years; 47.6% male). Meta-analysis of 11 studies showed a pooled mean NLR of 2.74 in ALS patients [95% CI (2.42, 3.10);