Reference values for serum cystatin C in very low-birthweight infants: From two centres of China

Aim: To determine the level of cystatin C (Cys-C) values in preterm babies for the purpose of becoming a good endogenous marker of renal function. Methods: A total of 366 very low-birthweight infants (including 70 extremely low-birthweight babies) with gestational age <37 weeks born in two centres were studied. Results: In very low-birthweight infants, the mean level of Cys-C was 1.96 +/- 0.44 mg/L in blood samples taken on day 1, 1.78 +/- 0.49 mg/L on day 7 and 1.71 +/- 0.47 mg/L on day 28. In extremely low-birthweight infants, the mean level of Cys-C was 2.00 +/- 0.49 mg/L on day 1, 1.63 +/- 0.38 mg/L on day 7 and 1.62 +/- 0.55 mg/L on day 28, respectively. Compared to serum creatinine and blood urea nitrogen, Cys-C level was independent of birthweight and gestational age. Conclusion: Cys-C is regarded as an alternative for assessing renal function in very low-birthweight infants, but its advantages over serum creatinine and blood urea nitrogen has not been fully proved yet. Hence, larger sample study is still necessary.