The Neutrophil to Lymphocyte Ratio in Poststroke Infection: A Systematic Review and Meta-Analysis

Ischemic and hemorrhagic strokes have multiple downstream consequences for patients. One of the most critical is poststroke infection (PSI). The goal of this systematic review and meta-analysis was to critically evaluate the literature regarding the use of the neutrophil to lymphocyte ratio (NLR) as a reliable means to detect early PSI development, particularly poststroke pneumonia (PSP) development to help clinicians institute early interventions and improve outcomes. The following were the inclusion criteria: (1) cross-sectional, case-control, and cohort studies; (2) studies comparing NLR data from PSI or PSP patients to controls; and (3) studies with a control group of stroke patients without infection. There was not any language or publication preference. The Newcastle-Ottawa Scale was used by two writers to assess the quality of the included studies. We assessed the certainty of the associations with GRADE methods. Web of Science, PubMed, and Scopus were searched, and 25 studies were included in the qualitative review. Among them, 15 studies were included in the meta-analysis. Standardized mean difference (SMD) was reported with a 95% confidence interval (CI) for the NLR levels. Patients with PSI had significantly higher NLR levels than stroke patients without infection ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:mtext>SMD</a:mtext> <a:mo>=</a:mo> <a:mn>1.08</a:mn> </a:math> ; <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" id="M2"> <c:mtext>CI</c:mtext> <c:mtext> </c:mtext> <c:mn>95</c:mn> <c:mi>%</c:mi> <c:mo>=</c:mo> <c:mn>0.78</c:mn> <c:mo>‐</c:mo> <c:mn>1.39</c:mn> </c:math> , <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" id="M3"> <e:mi>P</e:mi> </e:math> value < 0.001). In addition, the NLR levels of the stroke patients with pneumonia were significantly higher than those without pneumonia ( <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" id="M4"> <g:mtext>SMD</g:mtext> <g:mo>=</g:mo> <g:mn>0.98</g:mn> </g:math> ; <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" id="M5"> <i:mtext>CI</i:mtext> <i:mtext> </i:mtext> <i:mn>95</i:mn> <i:mi>%</i:mi> <i:mo>=</i:mo> <i:mn>0.81</i:mn> <i:mo>‐</i:mo> <i:mn>1.14</i:mn> </i:math> , <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" id="M6"> <k:mi>P</k:mi> </k:math> value < 0.001). However, data extracted from the qualitative review suggested that NLR could not predict urinary tract infection, sepsis, or ventriculitis in stroke patients. Our study indicated that NLR could be recommended as an inexpensive biomarker for predicting infection, particularly pneumonia, in stroke patients. It can help clinicians institute early interventions that can reduce PSI and improve outcomes.