The role of urine neutrophil gelatinase associated lipocalin as an early marker of Aki in sick neonates admitted into the special care baby unit of University of Port Harcourt Teaching Hospital

Abstract

Background: Neonatal acute kidney injury (NAKI) is relatively common, with increasing incidence globally. Infants with NAKI are at increased risk of long-term chronic kidney disease, or death.

Although serum creatinine is still presently used as an index of renal function, it is an insensitive  and poor marker of renal injury. The use of serum creatinine leads to delay in the detection and intervention in the early periods of renal injury when appropriate management strategies can be instituted before irreversible renal damage occurs.

Urine NGAL is presently the most expressed protein in the kidney following ischemia and has  been found to be a very sensitive and specific early marker of AKI before renal failure sets in.

Early diagnosis of NAKI using urine NGAL will aid in earlier institution of measures which will  improve clinical outcome in patients with AKI. This study will establish the role of urine NGAL as an early marker of NAKI in our setting.

Materials and methods: Two hundred and thirty ill neonates greater than 34weeks gestational age admitted into the special care baby unit of UPTH were consecutively recruited into the study. Serum for creatinine estimation was obtained on the third and fifth day of life respectively. Neonatal acute kidney injury (NAKI) was defined as an increase in serum creatinine by >26umol/l within 48hours.

Spot urine obtained in the first 48 hours of life was used for urine NGAL assessment. NAKI was defined as an increase in urine NGAL > 210ng/ml on the urine sample within the first 48hours of life.

Results: Urine NGAL detected more neonates with NAKI in the first 48 hours of life, before there was a rise in serum creatinine between the 3rd and 5th day, giving an incidence of NAKI of 38.3% and 23.5% using urine NGAL and serum creatinine respectively. Area under the curve (AUC) =0.722; 95% confidence interval: 0.644 – 0.799; p value= 0.0001 Urine NGAL of > 210ng in the first 48 hours of life in at risk neonates had a relatively significant diagnostic performance with a sensitivity of 70% and specificity of 72%. Although the positive predictive value of urine NGAL was relatively low (43%), the negative predictive value was high (89%) which implies that a urine NGAL of <210ng/ml as early as the first 48hours of life significantly excludes the diagnosis of NAKI in at risk new-borns.

Conclusion; Tertiary care facilities caring for critically ill new-borns such as those with severe birth asphyxia should routinely screen as early as the first 48hours of life using urine NGAL to exclude neonatal acute kidney injury.