Metabolic abnormalities associated with elevated serum cystatin C in adults with an estimated GFR ≥ 60 ml/min/1.73m 2

Elevated serum cystatin C may represent an early stage of kidney disease. It is unclear whether metabolic abnormalities typically seen in advanced chronic kidney disease are present in adults with estimated glomerular filtration rate ≥ 60 ml/min/1.73m 2 and elevated cystatin C. Participants of the Third National Health and Nutrition Examination Survey (n=6722) were categorized into three groups: estimated glomerular filtration rate ≥ 60 ml/min/1.73m 2 and cystatin C <1.09 mg/L (normal cystatin C); estimated glomerular filtration rate ≥ 60 ml/min/1.73m 2 and cystatin C ≥ 1.09 mg/L (elevated cystatin C); and estimated glomerular filtration rate of 15-59 ml/min/1.73m 2 (stage 3 or 4 chronic kidney disease). Among those with normal cystatin C, elevated cystatin C, and stage 3 or 4 chronic kidney disease, the age, race-ethnicity, sex standardized prevalence of serum hemoglobin <12 g/dL (<13 g/dL for men) was 4.3%, 8.2%, and 13.8%; serum uric acid ≥ 5.9 mg/ dL ( ≥ 7.4 mg/dL for