Determination of reference values for urinary neutrophil gelatinase-associated lipocalin in premature infants

Evaluation of uNGAL and TIMP-2*IGFBP7 as early biomarkers of Acute Kidney Injury in Caucasian term and preterm neonates: a prospective observational cohort study

BACKGROUND

Early diagnosis of Acute Kidney Injury (AKI) in neonates is a complex challenge. Novel urinary biomarkers such as uNGAL and TIMP-2*IGFBP7 may be helpful for predicting AKI earlier than changes in serum creatinine (sCr) and urinary output (UOP) in the neonatal period. uNGAL is a marker of tubular injury and its concentration rises immediately after AKI, while the proteins TIMP-2 and IGFBP7 jointly participate in the G1 phase cell cycle arrest processes and their tubular expression and urinary excretion increase in response to kidney damage. The aim of this study is to determine urinary concentrations of uNGAL and TIMP-2*IGFBP7 in term and preterm newborns and to evaluate their predictive role of AKI.

METHODS

Forty-two heathy term neonates and twenty-six preterm infants were prospectively recruited at the NICU of Policlinico in Bari, Italy. uNGAL and TIMP-2*IGFBP7 were measured in fresh urinary samples collected via perineal bag either before discharge (term neonates) or over the first week of life (preterm neonates).

RESULTS

In term neonates median uNGAL and TIMP-2*IGFBP7 concentrations were 41.40 ng/ml (IQR 20.25-74.5) e 0.22 (ng/ml)2/1000 (IQR 0.14-0.34), respectively. In preterm infants without AKI, uNGAL median concentrations over the first week of life ranged between 10 and 16 ng/ml, whereas median concentration of TIMP-2*IGFBP7 ranged between 0.05 and 0.08 (ng/ml)2/1000. Preterm infants who developed AKI during the first week of life had significantly higher uNGAL median concentrations compared to preterm infants without AKI (148.5 vs. 10.0, p = 0.04; 324.0 vs. 15.75, p = 0.02; 318.0 vs. 16.0 ng/ml, p = 0.04). Conversely, TIMP-2*IGFBP7 did not significantly increase in preterm infants with AKI. Preterm female neonates without AKI had significantly higher uNGAL than male neonates (46.5 vs. 10.0 ng/ml; Mann-Whitney U-test, p =0.013).

CONCLUSIONS

Our data show that uNGAL could be more useful than TIMP-2*IGFBP7 for early detection of AKI in preterm newborns. Further studies are needed to evaluate the role of both biomarkers during AKI and their relationship with gender, gestational age and birth weight.

Urine neutrophil gelatinase-associated lipocalin concentration in healthy newborns during the first three postnatal days

Introduction

Urine neutrophil gelatinase-associated lipocalin (uNGAL) is a biochemical marker significant for early prediction of acute kidney injury in adults. However, it has not been examined sufficiently among the infant population, particularly newborns in terms of reference values. The aim of our study was to determine the concentration of uNGAL in healthy term newborns and to determine if there was a difference in uNGAL concentration according to gender, postnatal age and birth weight.

Materials and methods

Our study involved 81 healthy term newborns birth (≥ 37 weeks, Apgar score ≥ 8 in the first minute after birth, CRP < 5 mg/L). Urine NGAL was measured using chemiluminescent microparticle immunoassay (CMIA) within 72 hours after birth, on Architect plus ci8200 analyser (Abbott, Chicago, USA). Data were analysed using Statistica software.

Results

The median concentration of uNGAL in the whole study group of healthy term newborns was 27.1 ng/mL (16.5-56.0 ng/mL) (newborn girls, 27.1 ng/mL (15.8-47.9 ng/mL); newborn boys, 27.9 ng/mL (16.5-61.0 ng/mL), P = 0.941). Median uNGAL concentration according to postnatal age expressed in days was 28.2 ng/mL (11.7-57.2 ng/mL) 1^st day, 28.9 ng/mL (16.5-64.2 ng/mL) 2^nd day and 23.9 ng/mL (20.2-46.6) 3^rd day, P = 0.863. Regarding birth weight for newborns < 3500 g, median concentration was 25.0 ng/mL (16.5-45.4 ng/mL) and for weight ≥ 3500 g 30.6 ng/mL (16.5-64.2 ng/mL), P = 0.455.

Conclusions

There were no significant difference in uNGAL concentration in relation to gender, postnatal age and birth weight.

Urine biomarkers for monitoring acute kidney injury in premature infants

Background

Premature infants are at high risk for acute kidney injury (AKI). Serum creatinine (Cr) has limitations for evaluating kidney function in premature infants. We evaluated whether urine biomarkers could be used to monitor AKI in premature infants.

Methods

A prospective cohort study was conducted among infants born at < 37 weeks. Urine biomarkers and serum Cr were measured on postnatal days 1, 3, 5, 7, 10, and 14. Infants were divided into 3 groups according to gestational age (GA); < 28, 28 to < 32 and 32 to < 37 weeks.

Results

AKI occurred in 17 of 83 (20.5%) recruited infants at a median age of 7 (interquartile range 5–10) days. While the most common cause of AKI was hemodynamically significant patent ductus arteriosus (53.8%) in infants of GA < 28 weeks, necrotizing enterocolitis was the leading cause (50.0%) in infants of GA 28 to < 32 weeks. Urinary levels of neutrophil-gelatinase-associated lipocalin/Cr were higher and epidermal growth factor/Cr were lower in AKI group before the onset of AKI in infants of GA < 28 weeks. In infants of GA 28 to < 32 weeks, urinary interleukin-8/Cr levels were higher in AKI group at approximately the time of AKI onset.

Conclusion

Several urine biomarkers were significantly different between AKI and no AKI groups, and some had changed before the onset of AKI. These groups were distinct according to causative factors of AKI and GA. Urine biomarkers could be useful for monitoring the development of AKI in premature infants.

Drug-induced renal injury in neonates: challenges in clinical practice and perspectives in drug development

Acute kidney injury (AKI) is frequently diagnosed in the neonatal population, especially in those admitted to intensive care units, and poses several challenges for clinicians mainly because of difficulties in timely identification of renal impairment and the need to administer drugs with potential nephrotoxicity. In this context, research on biomarkers is growing for their implication in the early detection of renal damage and their higher sensitivity in monitoring renal activity, but also as an important tool for drug development. Areas covered: We described the tools currently used to detect renal damage in neonatal settings, their limits and applicability, as well as the role of drugs on renal toxicity occurrence. Subsequently, we discuss current knowledge on new biomarkers for the detection of kidney injury and drug-induced kidney injury in neonates, and the qualification programs developed by regulatory agencies for biomarkers intended as tools in drug development. Expert opinion: Some molecules are emerging as potential biomarkers for early detection of AKI: promising data has demonstrated higher sensitivity and accuracy compared with tools currently used in the clinical setting. In addition, novel techniques (e.g. high power magnetic resonance imaging) to assess long-term consequences of AKI in neonates are in early steps of development.

Urinary Neutrophil Gelatinase-Associated Lipocalin Levels in Neonates

BACKGROUND

Acute kidney injury (AKI) is common in preterm infants and is associated with high mortality and morbidity. New biomarkers for the early detection of AKI have been identified. Specifically, urinary neutrophil gelatinase-associated lipocalin (uNGAL) is a new and powerful biomarker for AKI and sepsis. Our study evaluated the reference range of uNGAL in healthy neonates in Taiwan.

METHODS

This study examined 24 preterm and 38 term infants without clinical complications. Urine samples were collected and the uNGAL values were measured at postnatal age (PNA) 3 days, 7 days, 14 days, and 21 days in the preterm infants and at PNA 3 days in the term infants. The uNGAL values were tested using enzyme-linked immunosorbent assay.

RESULTS

The median uNGAL values in the preterm infants at PNA 3 days, 7 days, 14 days, and 21 days were 41.52 ng/mL, 35.82 ng/mL, 43.79 ng/mL, and 30.85 ng/mL, respectively. The median value at PNA 3 days in the term infants was 88.1 ng/mL. No significant differences associated with gestational age, birth body weight, or PNA were observed among the preterm infants. However, the uNGAL values in the female term infants were higher than those in the male term infants (p = 0.003).

CONCLUSION

This study presents preliminary data on uNGAL levels in neonates in Taiwan. A large-scale study investigating the correlations between uNGAL and with gestational age, birth body weight, sex, and PNA is recommended.