September 20, 2022
3 min read
Ku announces ownership interest in Edison Company; Received research grants from CareDx, Natera, and NIH; and serves as Associate Editor and Advisory to the American Kidney Fund Health Equity Coalition.
In a theoretical context, the 2021 creatine-based Chronic Kidney Disease Epidemiology Collaboration equation reduced racial disparities in preventive waiting time more than using the creatinine-cystatin equation, this study shows.
Therefore, the race-free, creatinine-based eGFR equation could reduce race differences to preventive wait times, the researchers wrote.
As Healio previously reported, Elaine Ku, MD, MAS, from the University of California, San Francisco, and colleagues found that including race in the eGFR equations resulted in a shorter time to kidney failure in black patients. This study found a similar time to kidney failure in black and white patients when using the new race-free equation.
In this retrospective cohort study, Ku and colleagues evaluated black-and-white patient data from the Chronic Renal Insufficiency Cohort (CRIC) study to determine whether the 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations measuring eGFR and eligibility for preventive treatment. The waiting list would correlate with racial differences in the accumulation of waiting times.
Two theoretical cohorts of patients potentially eligible for preventive wait time credit were created using either the CKD-EPI creatinine equation 2021 or the combined creatinine-cystatin C equation 2021 CKD-EPI to measure GFR .
All patients reported at least one eGFR less than 25 mL/min per 1.73 m2 and a subsequent eGFR of at least 20 mL/min per 1.73 m2 during their participation in the CRIC study using the 2021 CKD-EPI equations.
Researchers ran Weibull models of accelerated downtime and cause-specific hazards to identify the relationship between race and time to kidney failure from the qualifying visit when a patient’s eGFR dropped to at least 20 mL/min per 1.73 m2. In addition, the researchers used the 2021 creatinine or creatinine-cystatin C-based equation through a bootstrapping approach to assess differences in the time ratios of models.
A total of 472 patients were eligible for waitlist enrollment when the creatinine equation was used, and the potential preventive wait time was similar for black and white patients. In contrast, when the creatinine-cystatin C equation was used, 441 patients were eligible for waiting-list enrollment, and the potential waiting time was 20% shorter for Black patients than for White patients.
Using the creatinine equation, the mean waiting time that could occur for black patients was 23 months versus 22 months for white patients; whereas the median latency that could be incurred for black versus white patients using the creatinine-cystatin C equation was 21 months and 26 months, respectively.
Bootstrapping showed a significant difference in the time ratio of models using the creatinine vs. creatinine-cystatin C equation.
“We believe the results of our study are helpful in providing some preliminary data on how using the various GFR estimation equations would theoretically affect the waiting time before starting dialysis,” Ku said in the press release. “We found that the new creatinine-based equation appeared to be associated with a similar latency period compared to using the cystatin-C-based equation that could potentially be incurred, but our results require further validation in larger patient populations.”
In an accompanying editorial Rhiannon D Reed, MPH, DrPH, Assistant Professor at the Heersink School of Medicine and Jayme E Locke, MD, MPH, FACS, FAST, a transplant surgeon and director of the Department of Transplant Surgery at the University of Alabama at Birmingham and director of the Comprehensive Transplant Institute at the university, wrote: “We commend the authors for this well-designed study, which encourages future work to explore the costs and policy implications of wide availability of cystatin C and genetic lineage testing; the need for data on the impact of the race-free equation in other areas of clinical decision-making based on renal function; and further refinement of formulas that leverage existing clinical measurements, minimize bias and maximize accuracy.”