Prognostic Value of Neutrophil/Lymphocyte Ratio for Pulmonary Embolism: A Meta-Analysis and External Validation

Abstract

BackgroundPrognostic value of neutrophil/lymphocyte ratio (NLR) for pulmonary embolism (PE) has been reported in several retrospective studies. The purpose of this investigation was to perform a pooled analysis and external validation of predictive value of NLR. Material and methodPubMed, Embase, and Cochrane databases were searched from inception to November 5, 2022. A random effects model was used. Grade was used to evaluate the certainty of evidence. External validation was conducted in clinical cohorts before and after a propensity scoring matching (PSM). Covariates include basic clinical characteristics, such as age, gender, etc. The value of NLR in prediction model was also evaluated. ResultsA total of 15 studies comprising 5,874 patients were included. Pooled risk ratio (RR) of NLR was 2.33 [95% confidence interval (CI):1.97-2.75], with an area under the curve (AUC) of 0.78 (95% CI:0.74-0.81), a sensitivity of 0.75 (95% CI:0.71-0.79), a specificity of 0.67 (95% CI:0.61-0.73), and a median cut-off value of 5.7. GRADE certainty analysis showed the quality of the evidence was moderate. Before (n=336) and after (n=152) PSM, RR of NLR was 2.69 (95% CI:1.04-6.97) and 6.58 (95% CI:1.99-17.75). A prediction model consisting of NLR, age, D-dimer and simplified pulmonary embolism severity index (sPESI) had an AUC of 0.809 (95% CI:0.738-0.88), a sensitivity of 0.638 (95% CI:0.511,0.745), and a specificity of 0.851 (95% CI:0.709,0.917). Net reclassification index (NRI) (12%, p=0.035) and integrated discrimination improvement (17%, p=0.022) indicated an improvement caused by NLR. ConclusionPrognostic value of NLR for PE was confirmed by meta-analysis and validated in an independent cohort, deserving further clinical application.