Raceless Equation Underestimates Glomerular Filtration Rates in African Americans

By Will Boggs MD

March 18, 2020

NEW YORK (Reuters Health) - Removing race from the guideline-recommended glomerular filtration rate (GFR)-estimating equation for adults results in significant underestimation of GFR in African Americans, researchers report.

"As recommended by current guidelines, we should continue to use the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation as the first test, with the African American coefficient for patients who self-identify as African American, and without the African American coefficient for patients who do not (including mixed race combinations) or if race is not specified," Dr. Andrew S. Levey of Tufts Medical Center, in Boston, told Reuters Health by email.

Some have suggested eliminating race from the equation because race is a social rather than a biological construct and people self-define their race in so many different ways that any single category is flawed.

Dr. Levey's team used data from 8,254 individuals, 2,601 of whom were African Americans, who had measured GFR values to compare estimated GFR with and without including patient race in the analysis.

Eliminating the race coefficient in the CKD-EPI equation resulted in an underestimation of measured GFR throughout the range of GFR estimated by creatinine level for African Americans.

Moreover, a new equation that substituted height and weight for race was associated with worse performance overall and more so in African Americans than in others, the researchers report in JAMA Internal Medicine.

"We are concerned that the strategy of eliminating race from the equation may have unintended consequences in African American individuals, such as inappropriate early transplant or dialysis initiation, overdiagnosis of CKD, overestimation of the association of the risk of adverse outcomes with reduced GFR, inadequate dosing of drugs excreted by glomerular filtration (e.g., some antibiotics and cancer chemotherapy), and limited access to tests (e.g., some imaging procedures) and treatments that require a higher level of GFR (e.g., metformin, sodium-glucose cotransporter 2 inhibitors, bisphosphonates), including living kidney donation," the authors write.

"The goal should be to maintain and improve accuracy of GFR estimates and to avoid disadvantaging any racial group," Dr. Levey said. "Use of filtration markers in addition to serum creatinine, such as cystatin C, can allow less reliance of race in GFR estimation without loss of accuracy."

"Going forward," Dr. Levey said, "it would be preferable to avoid using race in GFR estimation."

Dr. Anders Kallner of Karolinska University Hospital, in Stockholm, who has argued that the large interindividual biological variation in GFR typically results in underestimation of GFR by most algorithms, told Reuters Health by email, "The idea of eGFR is fundamentally wrong - statistics is irreversible, meaning that an average cannot be applied to an individual with any reasonable confidence."

"Physicians around the world have been fooled by the false simplicity of the eGFR," said Dr. Kallner, who was not involved in the study.

SOURCE: https://bit.ly/38QjbDL JAMA Internal Medicine, online March 16, 2020.