Value of Neutrophil to Lymphocyte Ratio in Early Prediction of Meconium Aspiration Syndrome

Abstract Meconium aspiration syndrome (MAS) is a serious neonatal condition. Prediction of MAS is challenging particularly in low-resource setting. Neutrophil to lymphocyte ratio (NLR) is a new simple index used for diagnosis of many inflammatory conditions. The present study was an attempt to determine whether NLR can predict the occurrence of MAS. The present study included 101 children with meconium-stained amniotic fluid. They comprised 22 patients who developed MAS and 79 neonates who didn't have the condition. All neonates were subjected to careful analysis of maternal and perinatal history in addition to thorough clinical assessment and radiological and laboratory evaluation. Blood samples from the umbilical cord were collected at birth and were used to obtain complete blood counts and C-reactive protein (CRP) assay. Univariate analysis revealed that elevated CRP levels, increased NLR, and 5-minute Apgar score of <7 were significant risk factors for the occurrence of MAS. Multivariate analysis revealed that low 5-minute Apgar score and increased NLR remained as significant risk factors of MAS. Receiver operating characteristic curve analysis showed good performance of NLR in prediction of MAS. NLR is useful in prediction of MAS in term neonates with meconium-stained amniotic fluid.


Introduction
Meconium aspiration syndrome (MAS) is a neonatal lung injury induced by meconium aspirated into the lung and airways. 1 It is associated with significant mortality 2 and morbidities including persistent pulmonary hypertension and pneumonitis 3,4 particularly in developing countries. [5][6][7] It is crucial to identify infants at high risk of acquiring MAS and to distinguish cases with severe disease. This constitutes the cornerstone of effective prevention and treatment strategy in low-resource setting. 8 It is thought that fetal systemic inflammation is an important pathological mechanism in the development of MAS. 9 Labora-tory markers investigated to assess the role of inflammation in MAS included C-reactive protein (CRP) levels, immature-tototal neutrophil (IT) ratio, 10 and toll-like receptors levels. 11 Neutrophil to lymphocyte ratio (NLR) is a novel marker of inflammation that was extensively investigated in a wide range of medical conditions affecting adults 12-15 and children. [16][17][18][19] In neonates, increased level of NLR was related to patency of patent ductus arteriosus in preterm infants, 20 low survival in patients with solid tumors, 21 neonatal sepsis, 22 and neonatal necrotizing colitis. 23 The present study aims to assess the value of NLR in the prediction of MAS and its relation to disease severity.

Abstract
Meconium aspiration syndrome (MAS) is a serious neonatal condition. Prediction of MAS is challenging particularly in low-resource setting. Neutrophil to lymphocyte ratio (NLR) is a new simple index used for diagnosis of many inflammatory conditions. The present study was an attempt to determine whether NLR can predict the occurrence of MAS. The present study included 101 children with meconium-stained amniotic fluid. They comprised 22 patients who developed MAS and 79 neonates who didn't have the condition. All neonates were subjected to careful analysis of maternal and perinatal history in addition to thorough clinical assessment and radiological and laboratory evaluation. Blood samples from the umbilical cord were collected at birth and were used to obtain complete blood counts and C-reactive protein (CRP) assay. Univariate analysis revealed that elevated CRP levels, increased NLR, and 5-minute Apgar score of <7 were significant risk factors for the occurrence of MAS. Multivariate analysis revealed that low 5-minute Apgar score and increased NLR remained as significant risk factors of MAS. Receiver operating characteristic curve analysis showed good performance of NLR in prediction of MAS. NLR is useful in prediction of MAS in term neonates with meconium-stained amniotic fluid.

Materials and Methods
The present study was a prospective case-control study. It was conducted at Pediatric Department, Mansoura General Hospital, Mansoura, Egypt. All singleton term neonates with meconium-stained amniotic fluid (MSAF) at delivery in the period from January, 2013 through December, 2017 were included in the study. Among them, neonates with MAS were diagnosed on the basis of clinically manifest respiratory distress within 24 hours after birth and radiologically evident pneumonitis or air-trapping. Neonates with congenital anomalies and those with risk factors or evidence of neonatal sepsis were excluded from the study. All neonates were subjected to careful analysis of maternal and perinatal history in addition to sophisticated clinical assessment and radiological and laboratory evaluation. Blood samples from the umbilical cord during the 1st hour after delivery were used to obtain complete blood counts and CRP assay.
All the 117 neonates included in the study had MSAF at recruitment. However, 16 of those neonates were excluded from the study because they had one or more of the exclusion criteria. Among the remaining 101 neonates, those who later developed MAS (n ¼ 22) were considered as the study patients, while the 79 neonates who didn't have the condition served as controls. Patients with MAS were classified as having severe disease if they needed assisted ventilation for more than 48 hours or nonsevere disease if they required such intervention for less than 48 hours. 24 Informed consent was obtained from the legal guardians of all participants and the study was conducted according to the guidelines of the Declaration of Helsinki and was approved by the local ethical committee.
Statistical analysis was achieved using SPSS, version 22 (IBM, Armonk, New York, United States). Categorical variables were expressed as number and percent, while continuous data were represented as mean and standard deviation. Student's t-test was used for continuous data comparisons, while Fisher's exact test was used to compare categorical data. Logistic regression analysis was performed to reveal predictors of MAS. Only significant factors in univariate analysis were advanced into multivariate analysis. Receiver operating characteristic (ROC) curve analysis was utilized to assess the diagnostic value of NLR. A p-value less than 0.05 was considered statistically significant.

Results
The present study included 22 neonates with MAS and 79 neonates with MSAF. The latter group served as control group. Comparison between both groups regarding the basic laboratory data is illustrated in ►Table 1.

Discussion
The present study provides the first report of using the simple NLR in the prediction of MAS in absence of concomitant septicemia. In our study, NLR showed significant value in prediction of MAS both in univariate and multivariate analysis with a good sensitivity and specificity. In comparison, the work of Hofer et al 10 assessed the relationship between absolute neutrophil count and IT ratio in addition to CRP and MAS. They found significant association between elevated IT ratio and CRP levels and MAS severity. However, their study   didn't include control group and so, the diagnostic value of these markers wasn't assessed. Use of NLR in the diagnosis of inflammatory neonatal complications in the absence of microbial infection was previously reported. In the study of Kurtul et al, 25 neonates with retinopathy of prematurity showed significantly higher NLR when compared with controls.
The lower lymphocyte counts in MAS patients in our study may be explained by the exaggerated response to the steroid surge of labor 12,26 in which the role of lymphocyte corticosteroid receptors was implicated. [27][28][29] The diminished lymphocyte population could result in enhanced inflammatory process by reducing expression of intereukin-10; the main anti-inflammatory cytokine detected in patients with MAS and rise of the proinflammatory cytokines including intereukin-6, tumor necrosis factor α, and interferon gamma. 30 However, these mechanisms remain to be elucidated.
The present study has the strength of its prospective casecontrol design and long study period. However, our conclusions are limited by the relatively small sample size. From the practical point of view, performing differential leucocytic count is a widely available investigation even in low-resource settings and its use to distinguish neonates with MAS in the critical window of the first postnatal hour would provide a paramount help to the decision making in these situations. Findings of the present study are limited by the lack of cord blood gases analysis.

Conclusion
NLR is a useful tool for early prediction of MAS in term neonates with MSAF in the absence of sepsis/infection.

Funding
None.