Prognostic value of Neutrophil-to-lymphocyte ratio in COVID-19 patients: A systematic review and meta-analysis.

Ulloque-Badaracco, Juan R; Salas-Tello, W Ivan; Al-Kassab-Córdova, Ali; Alarcón-Braga, Esteban A; Benites-Zapata, Vicente A; Maguiña, Jorge L; Hernandez, Adrian V

BACKGROUND Neutrophil-to-lymphocyte ratio (NLR) is an accessible and widely used biomarker. NLR may be used as an early marker of poor prognosis in patients with COVID-19. OBJECTIVE To evaluate the prognostic value of the NLR in patients diagnosed with COVID-19. METHODS We conducted a systematic review and meta-analysis. Observational studies that reported the association between baseline NLR values (i.e. at hospital admission) and severity or all-cause mortality in COVID-19 patients were included. The quality of the studies was assessed using the Newcastle-Ottawa Scale (NOS). Random effects models and inverse variance method were used for meta-analyses. The effects were expressed as odds ratios (OR) and their 95% confidence intervals (CI). Small study effects were assessed with the Egger's test. RESULTS We analyzed sixty-one studies (n=15522 patients), 58 cohorts and three case-control. An increase of one unit of NLR was associated with a higher odds of severity (OR 6.22; 95%CI 4.93 to 7.84; p<0.001) and higher odds of all-cause mortality (OR 12.6; 95%CI 6.88 to 23.06; p<0.001). In our sensitivity analysis, we found that 41 studies with low risk of bias and moderate heterogeneity (I2 =53% and 58%) maintained strong association between NLR values and both outcomes (severity: OR 5.36; 95% CI 4.45 to 6.45; p<0.001; mortality: OR 10.42 95%CI 7.73 to 14.06; p=0.005). CONCLUSIONS Higher values of NLR were associated with severity and all-cause mortality in hospitalized COVID-19 patients.