Continuous reference intervals for plasma cystatin C and creatinine in Vietnamese children.

Background: Serum (plasma) creatinine and cystatin C are widely used in pediatric clinical practice to assess glomerular filtration rate. Both markers have limitations due to the low index of individuality, which affects the clinical sensitivity of population-based reference intervals, especially when wide age ranges are considered. This study aimed to establish age-related reference intervals for plasma cystatin C and creatinine in Vietnamese children. Methods: A total of 454 children, equally divided between boys and girls, aged from 1 day to 18 years, were recruited from the outpatient clinic of Vietnam National Children's Hospital. None of the participants had kidney or infectious diseases. Plasma samples were analyzed for cystatin C and creatinine using standard clinical chemistry methods. Using the the Lambda-Mu-Sigma method, we derived centile charts showing dynamic changes in these biomarkers. Results: In this cohort, plasma creatinine levels were high at birth, declined to their lowest point between ages of 2 and 3 years, and then gradually increased until adulthood. Plasma cystatin C levels were also elevated at birth, decreased to a steady state around age of 2 year, and remained stable until age of 10 years. From ages 10 to 14 years, cystatin C levels slightly increased, followed by a decrease from ages 15 to 18 years. Conclusions: Accurate assessment of glomerular filtration in children requires reliable laboratory tests and age-specific reference intervals. Providing serum (plasma) cystatin C and creatinine reference intervals with appropriate age partitions is crucial for improving the clinical sensitivity for detecting renal dysfunction, especially during the first few years of life.