To summarize the current evidence on the prognostic value of neutrophil-to-lymphocyte ratio (NLR) on Autoimmune encephalitis (AE) patients.

Autoimmune encephalitis (AE) is an immune-mediated condition that results in inflammation of the brain. Given the involvement of the immune system, the neutrophil-lymphocyte ratio (NLR) holds promise as a biomarker for assessing prognosis, treatment response, and severity. We conducted a systematic review and meta-analysis to identify the evidence of NLR as a potential prognostic biomarker for AE in adults.

We systematically searched databases (PubMed, Embase, Scopus, Web of Science, and Google Scholar) until April 2024.  A meta-analysis using a random-effects model to estimate pooled effects was realized for each outcome and a narrative synthesis when this was not possible. The risk of bias was assessed with the NewCastle-Ottawa tool.

In our systematic search, we identified 416 relevant articles, selected 31 of these for full-text review, and finally, 18 of them were included in our study. Two meta-analyses, covering a total of six studies with 585 patients in total, demonstrated a significant increase in (NLR) values in patients with  (AE), with moderate heterogeneity.
One of the meta-analyses, which was based on three studies with 157 patients with AE and an (mRS) score < 3, revealed a significant increase (MD: 1.59; 95% CI 2:61, 0:56 I2=0%). On the other hand, the other meta-analysis, which included three studies with 428 patients with AE and an mRS score ≥ 3, also showed a significant increase (MD: 1.81; 95% CI 2:78, 0:85 I2=32%). In all included studies, a low risk of bias was reported.

We found that NLR is a useful tool for predicting poor outcomes in AE patients. However, we need more studies, especially prospective ones, in order to improve the evidence regarding this ratio.