The Utility of Peripheral Blood Leucocyte Ratios as Biomarkers in Neonatal Sepsis: A Systematic Review and Meta-Analysis

Background: Early stage diagnosis of neonatal sepsis (NS) remains a major roadblock due to non-specific symptoms and the absence of precise laboratory index tests. The full blood count is a relatively cheap, universal, and rapid diagnostic test. Method: This study assessed the diagnostic accuracies of immature-to-total neutrophil ratio (ITR), immature-to-mature neutrophil ratio (IMR), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) used in the diagnosis of NS. Included studies were retrieved by searching four major databases and relevant references, and reviewed based on the inclusion/exclusion criteria. Pooled sensitivities and specificities were calculated, I-2 was utilized to test for heterogeneity, and the source was investigated via meta-regression analysis. Results: Finally, 38 studies passed the eligibility criteria. A total of thirty-one studies (6,221 neonates) included data on the ITR, eight studies (1,230 neonates) included data on the IMR, seven studies (751 neonates) included data on the NLR, and two studies (283 neonates) included data on the PLR. The summary sensitivity estimates with 95% confidence interval (CI) for the ITR, IMR, NLR, and PLR tests were, respectively, 0.74 (95% CI: 0.66-0.80), 0.74 (95% CI: 0.54-0.88), 0.73 (95% CI: 0.68-0.78), and 0.81 (95% CI: 0.55-1.00). The summary specificity values for the ITR, IMR, NLR, and PLR tests were 0.83 (95% CI: 0.77-0.87), 0.89 (95% CI: 0.80-0.94), 0.69 (95% CI: 0.57-0.79), and 0.93 (95% CI: 0.81-1.00), respectively. The area under the summary receiver operating characteristic curves for the ITR, IMR, and NLR tests were 0.85 (95% CI: 0.82-0.88), 0.91 (95% CI: 0.88-0.93), and 0.75 (95% CI: 0.71-0.79). The PLR could not be evaluated because only two studies included pertinent data. Conclusion: The NLR test might not be sufficiently accurate in precisely diagnosing NS. The ITR and IMR tests alone can improve the accuracy of NS diagnosis, but the marked heterogeneity and the limited number of studies prevented us from reaching any definitive conclusions. Thus, further studies are warranted to validate these findings.

Automated summary

Early stage diagnosis of neonatal sepsis is still a challenging issue, and the full blood count can serve as a cheap, universal, and rapid diagnostic test. This study found that the immature-to-total neutrophil ratio, immature-to-mature neutrophil ratio, and neutrophil-to-lymphocyte ratio can improve the accuracy of neonatal sepsis diagnosis. However, further studies are needed to validate these findings due to heterogeneity and limited research.