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

Prognostic 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.

PubMed, 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.

A total of 15 studies comprising 5,874 patients were included. Pooled risk ratio of NLR was 2.33 (95% confidence interval [CI]: 1.97-2.75), with an area under the curve 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 of Recommendations Assessment Development and Evaluation (GRADE) certainty analysis showed the quality of the evidence was moderate. Before (n = 336) and after (n = 152) propensity scoring matching, risk ratio 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 PE severity index had an area under the curve 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 (12%, P = 0.035) and integrated discrimination improvement (17%, P = 0.022) indicated an improvement caused by NLR.

Prognostic value of NLR for PE was confirmed by meta-analysis and validated in an independent cohort, deserving further clinical application.