Cystatin C as a Renal Function Marker for Neonates

ABSTRACT

The prediction of acute kidney injury (AKI) is important in the management of neonates, and several renal biomarkers have been tested for clinical application. Cystatin C (CysC) is a promising marker of renal function, and its application in neonatal care showed several benefits. First, CysC levels are not affected by endogenous substances such as bilirubin, hemoglobin, and ketones in laboratory tests. Second, its level is not influenced by inflammation (e.g., sepsis), muscle mass, age, gender, or nutritional status. Third, CysC is not transmitted through the placenta. Fourth, standardized automated measurement methods are available. Fifth, CysC was shown to reflect renal maturation better than creatinine. Lastly, CysC was reported to change with a wider amplitude than creatinine, which allows a more sensitive detection of renal deterioration. Recently, several reference CysC levels for neonates, including premature infants, were reported. In the present review, we summarized information on serum CysC reference values from different studies. Few studies investigated the usefulness of CysC for predicting AKI in neonates with various diseases such as neonatal respiratory distress syndrome, sepsis, and neonatal asphyxia. Recent studies showed an association between serum CysC level and cardiovascular diseases or Alzheimer's disease, indicating that CysC may play a role as a marker for various diseases in the future. Although the use of CysC as a marker in neonatal care showed several benefits, reliable and detailed reference ranges need to be established, including those for neonates with diseases. In addition, other novel renal markers need to be tested in neonates.