Abstract
OBJECTIVES: Creatinine, the current clinical standard to detect chronic kidney disease (CKD), is biased by muscle mass, age and race. The authors sought to determine whether cystatin C, an alternative marker of kidney function less biased by these factors, can identify elderly Mexican Americans with CKD who are at high risk for death and cardiovascular disease. DESIGN: Longitudinal, with mean follow-up of 6.8 years. SETTING: Sacramento Area Latino Study of Aging (SALSA). PARTICIPANTS: One thousand four hundred and thirty five Mexican Americans aged 60 to 101. MEASUREMENTS: Estimated glomerular filtration rate (eGFR, mL/min per 1.73 m(2)) was determined according to creatinine (eGFRcreat) and cystatin C (eGFRcys), and participants were classified into four mutually exclusive categories: CKD neither (eGFRcreat ≥60 mL/min per 1.73 m(2); eGFRcys ≥60 mL/min per 1.73 m(2)), CKD creatinine only (eGFRcreat <60 mL/min per 1.73 m(2); eGFRcys ≥60 mL/min per 1.73 m(2)), CKD cystatin only (eGFRcreat ≥60 mL/min per 1.73 m(2); eGFRcys <60), and CKD both (eGFRcreat <60 mL/min per 1.73 m(2); GFRcys <60 mL/min per 1.73 m(2)). The associations between each CKD classification and all-cause death and cardiovascular (CV) death were studied using Cox regression. RESULTS: At baseline, mean age was 71 ± 7; 481 (34%) had diabetes mellitus, and 980 (68%) had hypertension. Persons with CKD both had higher risk for all-cause (HR = 2.30, 95% confidence interval (CI) = 1.78-2.98) and CV disease (CVD) (HR = 2.75, 95% CI = 1.96-3.86) death than CKD neither after full adjustment. Persons with CKD cystatin C only were also at greater risk of all-cause (HR = 1.91, 95% CI = 1.37-2.67) and CV (HR = 2.56, 95% CI = 1.64-3.99) death than CKD neither. In contrast, persons with CKD creatinine only were not at greater risk for CV death (HR = 1.39, 95% CI = 0.71-2.72) but were at higher risk for all-cause death (HR = 1.95, 95% CI = 1.27-2.98). CONCLUSION: Cystatin C may be a useful alternative to creatinine for detecting high risk of death and CVD in elderly Mexican Americans with CKD.