Creatinine at Birth Correlates with Gestational Age and Birth Weight: Another Factor of the Imbroglio in Early Neonatal Life.

BACKGROUND

Serum creatinine (Scr) in early neonatal life (first week of life) displays extensive variability; hence, a better understanding is needed to use Scr as a diagnostic biomarker for acute kidney injury (AKI).

OBJECTIVE

The objective of this study was to explore Scr trends and its covariates in early neonatal life.

METHODS

Analysis of a rich, pooled Scr dataset (enzymatic assay) of 4,509 Scr observations in 1,181 neonates in the first week of life with birth weight, gestational age (GA), and postnatal age as covariates was conducted. Descriptive data were summarized as median and range. The Spearman rank correlation test was used to examine Scr, while the Mann-Whitney U test was used to determine the differences between the different GA (≤32, 33-36, or ≥37 weeks) categories.

RESULTS

The median Scr at delivery was 55.7 (range 28.3-194.5) µmol/L, correlating with birth weight (r = 0.088) or GA (r = 0.183) for the full dataset. At birth, the median Scr was highest in term (≥37-week) neonates. In early neonatal life (median Scr values), there was a gradual increase to attain a peak Scr by day 2-3, highest and most delayed in neonates ≤32 weeks GA. This is followed by a blunted decrease when ≤32-week neonates were compared to those of 33-36 or ≥37 weeks GA.

CONCLUSIONS

The Scr pattern in early neonatal life is complex, with the highest Scr at birth in full-term neonates, while those ≤32 weeks GA displayed the highest and delayed peak Scr with a subsequent blunted decrease. Knowledge of these patterns is crucial to explore the utility of Scr as an AKI biomarker.