Prognostic value of the neutrophil-to-lymphocyte ratio in acute ischemic stroke patients treated with intravenous thrombolysis: a systematic review and meta-analysis

BACKGROUND: The relationship between the neutrophil-to-lymphocyte ratio (NLR) and poor prognostics in acute ischemic stroke (AIS) patients who receive intravenous thrombolysis (IVT) remains controversial. The purpose of this systematic review and meta-analysis was to evaluate the association between the NLR and poor prognosis after IVT. Furthermore, we aimed to determine whether the NLR at admission or post-IVT plays a role in AIS patients who received IVT. METHODS: The PubMed, Embase, Web of Science and China National Knowledge Infrastructure databases were searched for relevant articles until October 7, 2020. Cohort and case-control studies were included if they were related to the NLR in AIS patients treated with IVT. Odds ratios (ORs) and 95 % confidence intervals (95 % CIs) were pooled to estimate the relationship between NLR and poor prognosis after IVT. A random effects model was used to calculate the pooled data. RESULTS: Twelve studies, including 3641 patients, met the predefined inclusion criteria. Higher NLRs were associated with an increased risk of hemorrhagic transformation (HT) (OR = 1.33, 95 % CI = 1.14–1.56, P < 0.001) and a poor 3-month functional outcome (OR = 1.64, 95 % CI = 1.38–1.94, P < 0.001) in AIS patients who received IVT. Subgroup analysis suggested that the NLR at admission rather than post-IVT was associated with a higher risk of HT (OR = 1.33, 95 % CI = 1.01–1.75, P = 0.039). There was no statistically significant difference between higher NLRs and 3-month mortality (OR = 1.14, 95 % CI = 0.97–1.35, P = 0.120). CONCLUSIONS: A high NLR can predict HT and poor 3-month functional outcomes in AIS patients who receive IVT. The NLR at admission rather than the post-IVT NLR was an independent risk factor for an increased risk of HT after IVT. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12883-021-02222-8.