Reference ranges for 24-h urinary protein/creatinine ratio and urinary microalbumin/creatinine ratio in Chinese children.

Background: The purpose of this study was to investigate the age and gender characteristics of 24-h urinary protein/creatinine ratio (24hUPCR) and urinary microalbumin/creatinine ratio (UMACR) among Chinese children and other related factors, and to establish preliminary reference ranges.

Methods: A total of 200 healthy children aged 2-15 years were enrolled. We divided the subjects into twelve groups according to age. Kruskal-Wallis one-way ANOVA test and Spearman correlation analysis were used to compare 24hUPCR and UMACR with other variables and 95% reference range was used to establish the reference range.

Results: 24hUPCR and UMACR showed correlation with age, height, weight, and body mass index (BMI) (p < 0.001), and females had higher levels than males among all healthy children (p < 0.01). 6 and 8 years of age were the critical nodes in the change of 24hUPCR and UMACR levels, respectively. The reference ranges established based on the 200 Chinese children in this study are as follows: 24hUPCR: < 24.34 mg/mmol (male) and < 43.04 mg/mmol (female) for ≥ 2-6 years; < 17.60 mg/mmol (male) and < 22.80 mg/mmol (female) for ≥ 6-15 years.

Umacr:  < 1.53 mg/mmol (male) and < 1.74 mg/mmol (female) for ≥ 2-8 years, < 1.13 mg/mmol (male) and < 3.48 mg/mmol (female) for ≥ 8-15 years.

Conclusions: 24hUPCR and UMACR in children were correlated with age, gender, height, weight, BMI, and ethnicity. Establishing the right pediatric cutoff values that account for age, gender, and ethnicity can guarantee the sensitivity and specificity needed for clinical applications.