Comparison of measured GFR, serum creatinine, cystatin C, and beta-trace protein to predict ESRD in African Americans with hypertensive CKD

Background: Identification of persons with chronic kidney disease (CKD) who are at highest risk to progress to end-stage renal disease (ESRD) is necessary to reduce the burden of kidney failure. The relative utility of traditional markers of kidney function, including estimated glomerular filtration rate (eGFR) and serum creatinine level, and emerging markers of kidney function, including cystatin C and beta-trace protein (BTP) levels, to predict ESRD and mortality has yet to be established.

Study design: Randomized clinical trial followed by an observational cohort study.

Setting & participants: 865 African American individuals with hypertensive CKD enrolled in a clinical trial of 2 levels of blood pressure control and 3 different antihypertensive drugs as initial therapy and subsequently followed by an observational cohort study.

Predictors: Quintile of measured GFR (mGFR) by iothalamate clearance, serum creatinine, serum creatinine-based eGFR, cystatin C, and BTP values.

Outcomes & measurements: Incidence of ESRD and mortality.

Results: 246 participants reached ESRD during a median follow-up of 102 months. The incidence rate of ESRD was higher with higher quintiles of each marker. The association between higher BTP level and ESRD was stronger than those for the other markers, including mGFR. All markers remained significantly associated with ESRD after adjustment for mGFR and relevant covariates (all P < 0.05), with BTP level retaining the strongest association (HR for highest vs lowest quintile, 5.7; 95% CI, 2.2-14.9). Associations with the combined end point of ESRD or mortality (n = 390) were weaker, but remained significant for cystatin C (P = 0.05) and BTP levels (P = 0.004).

Limitations: The ability of these markers to predict ESRD and mortality in other racial and ethnic groups and in individuals with CKD due to other causes is unknown.

Conclusions: Plasma BTP and cystatin C levels may be useful adjuncts to serum creatinine level and mGFR in evaluating risk of progression of kidney disease.