Immature to total neutrophil ratio as an early indicator of early neonatal sepsis

Abstract

Background & objectives: Neonatal septicemia is responsible for 1.5 to 2.0 million deaths/year in the under developed countries of the world. Pakistan is number three among these countries and accounts for 7% of global neonatal deaths. The objective of the study was to determine the role of simple hematological parameter, immature to total neutrophil ratio (I/T ratio) in diagnosing early onset neonatal bacterial infection.

Methods: A descriptive cross-sectional study was conducted in Neonatal Intensive Care Unit of Liaquat College of Medicine & Dentistry (LCMD) Hospital from January 2016 to January 2017. A total 85 neonates were admitted with clinical suspicion of presumed early onset sepsis or who had potential risk factors for sepsis like prematurity, prolonged rupture of membranes was carried out. After taking informed consent from parents of admitted neonates, data was collected in a structured questionnaire. Laboratory workup included White blood cell count, CRP, absolute neutrophil count, immature neutrophil count while blood C/S was kept as gold standard. Empirical antibiotics started after sample collection for workup. Manual differential count and immature neutrophil count of the peripheral blood smear was performed by a senior technician masked to clinical information. I/T ratio was calculated from WBC, neutrophils and immature neutrophil count by a simple formula.

Results: Out of 85 neonates, 13 had positive blood cultures (15.29%). The mean white blood count was 18761.18 ± 8570.75 and mean I/T ratio was 0.1622 ± 0.0419. About 50% of proven sepsis cases had WBC higher than 26000 as compared to 50% of cases for negative diagnoses that had WBC <15500. The mean I/T in positive CRP 0.204 ± 0.04 was non-significantly higher as compared to negative CRP 0.151 ± 0.034 (p =0.084). Point biserial correlation revealed that I/T ratio was significant strong correlation (r_{pb =} 0.721, p < 0.001) and overall I/T ratio was a good indicator of a positive and negative blood culture result. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of I/T ratio were 76.47%, 83.82%, 54.16% and 93.44% respectively. Similarly majority of neonates having high I/T ratio also depicts positive C-reactive protein (CRP) (NPV 91.23%). Therefore, both I/T and CRP showed a high negative predictive value (I/T = 93.44% and CRP = 91.23%) in this study.

Conclusion: I/T ratio is a useful tool for early onset sepsis (EOS) with reasonable specificity but cannot be relied upon as sole indicator. Combination of normal immature to total neutrophil Ratio with negative CRP values in neonates with presumed sepsis is an indicator of non-infected neonate which comprised 78.8% of our study population.

Keywords: Blood culture; CRP; Early onset sepsis (EOS); I/T ratio; Neonatal Sepsis.