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