Kidney function reference values in US adolescents: National Health And Nutrition Examination Survey 1999-2008.

BACKGROUND AND OBJECTIVES: Few data are available on kidney function in normal US adolescents. This study characterizes the distribution of kidney function measures and associated factors. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Serum creatinine, cystatin C, and urinary albumin-to-creatinine ratios were measured in US adolescents (aged 12 to 17 years; n = 5575) in the cross-sectional National Health and Nutrition Examination Survey 1999-2008. The reference population was defined as healthy adolescents with BP <120/80 mmHg and a Z-score for weight-to-height ≤1.645, without self-reported diabetes or hypertension, not using prescription medications in the preceding 30 days, not pregnant or currently menstruating.
RESULTS: were analyzed by age, gender, race, ethnicity, body mass index, and BP; estimated GFR (eGFR) was calculated using the original and revised Schwartz formulas. Results Mean values for eGFR(Schwartz original formula), serum creatinine, and serum cystatin C were 147 ml/min/1.73 m(2), 0.71 mg/dl, 0.82 mg/L, respectively. The median urinary albumin-to-creatinine ratio was 6.8 mg/g creatinine. In the reference population (n = 2881), eGFR differed significantly using the two Schwartz formulas; values were higher using the original formula (median values 143 versus 96 ml/min/1.73 m(2)). Serum creatinine level (0.7 versus 0.72 mg/dl), but not cystatin C level (0.82 versus 0.82 mg/L), was lower in the reference population than in a nonreference population of adolescents.
CONCLUSIONS: These findings provide important demographic information and highlight the need for confirmatory testing of the revised Schwartz formula by comparison to measured GFR in healthy US adolescents.