Pediatric GFR Estimating Equations Applied to Adolescents in the General Population

Background and objectives We examined the distribution of estimated GFR (eGFR) in a healthy cohort of adolescents to inform clinical and research use. Design, setting, participants, & measurements Various creatinine-based (n = 3256) and/or cystatin C-based (n = 811) equations, including the recently developed complete and bedside equations from the Chronic Kidney Disease in Children (CKiD) study, were applied to U.S. adolescents 12 to 17 years of age participating in the 1999-2002 National Health and Nutrition Examination Survey (NHANES). Results The median serum creatinine and cystatin C were 0.7 mg/dl and 0.83 mg/L, respectively. The distribution of eGFR varied widely, with the median GFR ranging from a low of 96.6 ml/min per 1.73 m² (CKiD) to a high of 140.0 ml/min per 1.73 m² (original Schwartz). The proportions of participants with eGFRs <75 ml/min per 1.73 m² are as follows: bedside CKiD 8.9%, Counahan 6.3%, Leger 0.4%, original Schwartz 0%, Filler 1.3%, Grubb 3.1%, Bouvet 2.5%, CKiD 1.8%, and Zappitelli 5.6%. By any equation examined, no group of participants with eGFR ≤10th percentile had an increased prevalence of comorbid conditions consistent with a low measured GFR. Conclusions Most pediatric-specific GFR estimating equations resulted in 25% to 50% of the participants having an eGFR <100 ml/min per 1.73 m². However, participants with eGFR in the lower ranges did not have an increased prevalence of morbidities associated with chronic kidney disease. Clinical validation of creatinine- or cystatin C-based estimated GFRs in healthy children is needed before it is possible to screen the general population for chronic kidney disease.