The overlooked subgroup: preterm neonates with elevated serum creatinine outside neonatal AKI criteria.

BACKGROUND

To characterize risks and outcomes of preterm neonates with elevated serum creatinine (SCr) not meeting acute kidney injury (AKI) criteria.

METHODS

This cohort study included neonates <31 weeks' gestation admitted to a university hospital. Elevated SCr was defined as exceeding the 95th percentile for postnatal age without meeting standard AKI criteria in neonates <28 or 28-30 weeks. Perinatal/neonatal risks and discharge outcomes were compared among elevated SCr, SCr-AKI, and no SCr-AKI subgroups.

RESULTS

Among 810 infants, 156 had SCr-AKI, 623 had no SCr-AKI, and 31 had elevated SCr. Compared to no SCr-AKI, the elevated SCr subgroup had lower birthweight, higher rates of small-for-gestational-age, respiratory distress, hemodynamic instability, prolonged invasive ventilation, lower anthropometric z-scores, and higher mortality, despite similar gestational age. Compared to SCr-AKI, they had higher gestational age and higher rates of small-for-gestational-age, with similar mortality. Adjusted models showed elevated SCr (adjusted relative risk [aRR], 3.74) and SCr-AKI (aRR, 3.95) predicted higher mortality versus no SCr-AKI.

CONCLUSION

Gestational age-specific SCr references are critical for identifying preterm neonates with elevated SCr levels outside AKI criteria, who face neonatal risks and distinct mortality outcomes.

IMPACT STATEMENT: The risks and outcomes of preterm neonates with elevated serum creatinine (SCr) levels that do not meet Kidney Disease: Improving Global Outcomes (KDIGO) acute kidney injury (AKI) criteria require further investigation. These neonates have distinct exposure profiles compared to those with KDIGO SCr-AKI and a poorer prognosis than those without SCr-AKI. They also have higher mortality than neonates without SCr-AKI. Our findings highlight the importance of gestational age-specific SCr reference values in neonatal care to better identify at-risk preterm infants beyond KDIGO criteria, enabling early intervention and improved outcomes.