Cystatin C and creatinine in an HIV cohort: The Nutrition for Healthy Living Study

Background: Human immunodeficiency virus (HIV)-infected persons have an increased risk of chronic kidney disease (CKD). Serum creatinine level may underestimate the prevalence of CKD in subjects with decreased lean body mass or liver disease. Level of serum cystatin C, an alternative kidney function marker, is independent of lean body mass. Study Design: Cross-sectional. Setting & Participants: 250 HIV-infected subjects on highly active antiretroviral therapy in the Nutrition for Healthy Living (NFHL) cohort; 2,628 National Health and Nutrition Examination Survey (NHANES) 2001-2002 subjects. Predictors & Outcomes: Comparison of serum creatinine levels in NFHL to those in NHANES subjects; comparison of CKD in NFHL subjects ascertained using serum creatinine versus cystatin C levels. Measurements: Standardized serum creatinine, serum cystatin C, glomerular filtration rate (GFR) estimated from serum creatinine and cystatin C levels. Results: Creatinine levels were lower in NFHL than NHANES subjects despite greater rates of hepatitis, diabetes, and drug use (mean difference, -0.18 mg/dL; P < 0.001 adjusted for age, sex, and race). Of NFHL subjects, only 2.4% had a creatinine-based estimated GFR less than 60 mL/min/1.73 m(2), but 15.2% had a cystatin-based estimated GFR less than 60 mL/min/1.73 m(2). Limitations: GFR was estimated rather than measured. Other factors in addition to GFR may affect creatinine and cystatin C levels. Measurements of proteinuria were not available. Conclusions: Serum creatinine levels may overestimate GFRs in HIV-infected subjects. Kidney disease prevalence may be greater than previously appreciated.