Discussion

High NGAL levels in body fluids have been associated with many diseases especially acute kidney injury.(8,9,10) The risk of acute kidney injury (AKI) is higher in neonates than in other groups.(11,12,13) For this reason, early detection of AKI in neonates is vital. Current biomarkers in use are too late to show kidney injury. Studies have shown that NGAL can be used as a biomarker for early detection of AKI.(14) In addition, it was found valuable in other cases with ischemia and related tissue damage.
In the study of Krawczeski et al.(15),urine NGAL levels of neonates were significantly increased at the second hour after cardiopulmonary bypass surgery, while there were no changes in serum creatinine levels. If the cutoff value was taken as 185 ng/ml, the sensitivity and specificity of urine NGAL for AKI were 100% and 93%, respectively. It was stated that urine NGAL was an early and reliable marker in the diagnosis of neonatal AKI compared to serum creatinine. In another study conducted in critically ill neonates, serum NGAL levels increased earlier than serum creatinine in neonates who developed AKI. It was shown that, with or without sepsis, NGAL could be used as an early marker in neonatal AKI cases.(16) However, in a more recent study, Reiter et al.(17) stated that plasma and urine NGAL levels were not reliable markers for developing AKI in neonates after cardiac surgery with cardiopulmonary bypass. In our study, there was no patient diagnosed with AKI. They attributed increased NGAL levels to inflammation following cardiac bypass. As supported by these studies, NGAL increases in ischemic and inflammatory events, and this is only noticed when organ functions are affected. However, NGAL can be used in the early detection of organ damage. In our study, there was no statistically significant difference, such as low birth weight, prematurity and low Apgar score, and umbilical cord blood NGAL levels.
Sepsis is one of the major causes of AKI in neonates. In a study conducted by Pynn et al.(18), urine NGAL was pointed out as a non-invasive biomarker with high negative predictive value at the time of late-onset sepsis assessment in neonates. According to a study conducted by Parravicini et al.(4), on 91 very low birth weight infants, urine NGAL is a promising candidate as an early biomarker for sepsis and it was also shown that urinary NGAL levels was an early biomarker to detect sepsis. In our study, there was no statistically significant difference between the risk factors of sepsis, such as male gender, gestational age below 37 weeks and umbilical cord blood NGAL levels; however, there was a statistically significant difference between PROM, which is also a risk factor in sepsis, and umbilical cord blood NGAL levels. (18)
In a group of neonates with intrauterine hypoxia, Essajee et al.(20) found that urine NGAL is a predictor of mortality and hypoxic encephalopathy. Similar results were found in another study conducted by Fiala et al. (21). According to this study, NGAL has the potential to be a good marker for perinatal hypoxia and has high sensitivity and specificity. In our study, there was no statistically significant difference between the risk factors of asphyxia, such as cesarean section, low birth weight and preterm labor, and umbilical cord blood NGAL levels.
In a study conducted by Chen et al. (22) on 24 preterm and 38 term infants, it was found that there was no statistically significant difference between gestational age and birth weight and urine NGAL levels in preterm infants. The same study found that urine NGAL values of the female term infants were higher compared to male term infants. Another study reported that NGAL concentrations were higher in preterm female infants and decreased with higher gestational age.(23) In our study, there was no statistically significant difference between gestational age, gender, birth weight and umbilical cord blood NGAL levels.
In clinical practice, there is always a need for markers that predict complications and divide patients into risk categories so that they can be diagnosed and treated early. If NGAL takes its place in routine use as a diagnostic biomarker, it will contribute greatly to the development of new treatment approaches. In our study, the desired number of patients could not be reached in some groups. Also, the limited number of similar studies on this biomarker reduces the comparability of our study. In order to accurately determine the effects of specific perinatal risk factors on umbilical cord blood NGAL levels, multivariate analyses and comprehensive studies in large numbers of neonates with specific risk factors isolated are required.
In this study, the relationship between umbilical cord blood NGAL levels and neonatal diseases was examined. As there are only a few studies in the literature on umbilical cord blood NGAL levels, this study was compared with studies that examined urine and serum NGAL levels and their relationship to certain diseases. However, further studies on larger patient populations are needed.
Table 1: The relationship between demographic characteristics and NGAL levels