Measuring cystatin C to determine renal function in neonates

The incidence of acute kidney injury in neonates is high and associated with up to a 50% mortality rate. The purpose of this review was to determine the feasibility of using serum cystatin C measurements to assist clinicians in making early and accurate diagnoses of acute kidney injury in neonates.

We searched for the following seven key words within the PubMed database and the Cochrane Database of Systematic Reviews: cystatin C, neonates, newborn, preterm, premature, kidney failure, and kidney injury.

The selected studies included neonates within their study populations and were published in English. We reviewed literature published between January 1990 and May 2012.

Ten studies had conducted serum cystatin C measurements in neonates.

The cystatin C level in neonates is not influenced by the maternal level and is highest at birth. In most studies, cystatin C levels on day 1 of life ranged between 1 and 2 mg/L, gradually declined during the first year and then remained relatively stable thereafter. Cystatin C levels did not differ between male and female infants, and no significant gestational age-dependent differences were found. Cystatin C levels were increased in cases of sepsis, acute kidney injury, and congenital renal abnormalities.

Cystatin C has all of the theoretical properties needed to be an ideal marker of renal function. It can be used to determine baseline renal function on day 1 and is increasingly being used to determine renal function in sick neonates. In the majority of studies, the day 1 cystatin C level ranged between 1 and 2 mg/L, which gradually declined in the first year of life. However, the number of available studies evaluating cystatin C in sick neonates is currently limited, and there are also no studies linking cystatin C levels in sick babies with short-term and long-term outcomes.