Estimating time to ESRD using kidney failure risk equations: results from the African American Study of Kidney Disease and Hypertension (AASK)

Abstract

Background: Planning for renal replacement therapy, such as referral for arteriovenous fistula placement and transplantation, often is guided by level of estimated glomerular filtration rate (eGFR). The use of risk equations might enable more accurate estimation of time to end-stage renal disease (ESRD), thus improving patient care.

Study design: Prospective observational study.

Setting & participants: 1,094 participants in the African American Study of Kidney Disease and Hypertension (AASK) cohort.

Predictor: Age, sex, urine protein-creatinine ratio ≥ 1g/g, APOL1 high-risk status, and 3-year antecedent eGFR decline.

Outcome: Cumulative incidence of ESRD from 5 different starting points: eGFR of 30 and 15mL/min/1.73m(2) and 1-year ESRD risk of 5%, 10%, and 20%, estimated by a published 4-variable kidney failure risk equation.

Results: 566 participants developed eGFR of 30mL/min/1.73m(2), 244 developed eGFR of 15mL/min/1.73m(2), and 437, 336, and 259 developed 1-year ESRD risks of 5%, 10%, and 20%, respectively. The 1-year cumulative incidence of ESRD was 4.3% from eGFR of 30mL/min/1.73m(2), 49.0% from eGFR of 15mL/min/1.73m(2), 6.7% from 5% ESRD risk, 15.0% from 10% ESRD risk, and 29% from 20% ESRD risk. From eGFR of 30mL/min/1.73m(2), there were several risk factors that predicted ESRD risk. From eGFR of 15mL/min/1.73m(2), only level of proteinuria did; median time to ESRD was 9 and 19 months in those with higher and lower proteinuria, respectively. Median times were less variable from corresponding ESRD risk thresholds. For example, median times to ESRD from 20% ESRD risk were 22 and 25 months among those with higher and lower proteinuria, respectively.

Limitations: Relatively homogeneous population of African Americans with hypertensive kidney disease.

Conclusions: Results of the present study suggest the potential benefit of incorporating kidney failure risk equations into clinical care, with selection of a specific threshold guided by its intended use.

Keywords: African American Study of Kidney Disease and Hypertension (AASK); End-stage renal disease (ESRD); clinical decision making; disease progression; disease trajectory; estimated glomerular filtration rate (eGFR); hypertensive kidney disease; kidney failure risk equations; prognosis; proteinuria; risk.

Figure 1

Cross-sectional distribution of eGFR and 1-year probability of end-stage renal disease at the first visit at which an AASK participant crosses the threshold of 5% 1-year ESRD risk (black circles), 10% 1-year ESRD risk (red circles), and 20% 1-year ESRD risk (green circles)

Figure 2

Cumulative incidence of end-stage renal disease and death prior to end-stage renal disease from eGFR 30 ml/min/1.73 m², eGFR 15 ml/min/1.73 m², and 5%, 10%, and 20% 1-year risk of end-stage renal disease† † Curves reflect cumulative incidence of ESRD and pre-ESRD mortality, where each outcome is treating as a competing event for the other. Confidence intervals were calculated by a boot-strap method using 10,000 repetitions. Models were adjusted to eGFR 30 and 15 ml/min/1.73 m2 in the eGFR threshold analyses and 5%, 10%, and 20% 1-year ESRD risk in the kidney failure risk threshold analyses. Solid circles represent incidence at 1 year.

Figure 3

Median (25^th percentile – 75^th percentile) times to end-stage renal disease, by patient characteristic, from five starting points: eGFR 30 ml/min/1.73 m², eGFR 15 ml/min/1.73 m², and 5%, 10%, and 20% 1-year risk of end-stage renal disease† †Times to end-stage renal disease estimated accounting for the competing risk of death and adjusting to eGFR 30 or 15 ml/min/1.73 m² in analyses from eGFR thresholds and 5%, 10%, and 20% 1-year end-stage renal disease (ESRD) risk in analyses from ESRD risk thresholds. Dashed lines represent an imputed interquartile range and are truncated at the last observed follow-up time.