Researchers who compared the 2009 equation used in British Columbia for estimating kidney function to a newer version have discovered the newer version estimates higher kidney function. The results, published in
Kidney International Reports, may hold important implications for determining a person’s stage of kidney disease and how they should be monitored.
To estimate a person’s kidney function, BC laboratories commonly use the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) 2009 equation, which accounts for the person’s age, sex, race and serum creatinine. In 2021, a modified version of the equation was released that does not account for race, and the researchers wanted to learn how the two different equations compare as estimating tools.
To explore this question, Mohammad Atiquzzaman, a research scientist with BC Renal, and his colleagues analyzed data from more than 11,600 kidney patients in British Columbia. They inputted the same data from each person into the two respective equations to estimate kidney function.
Both equations provide an estimated glomerular filtration rate (eGFR) that represents estimated kidney function. The results of the study show that the 2021 equation provides higher estimates of GFR than the 2009 equation. On average, the 2021 equation resulted in an eGFR of 2.7 ml/min per 1.73 m2 higher, with variation generally higher among men than women.
The researchers then looked at how the higher kidney function estimated by the 2021 equation would change how individuals are staged by kidney disease severity.
“Interestingly, what we found is that 17 percent of our patients in BC would be reclassified to a category with higher eGFR, which means more kidney function is preserved,” explains Atiquzzaman. “So their treatment strategy, their monitoring would be changed.”
He emphasizes how much these classifications mean for patients’ treatment strategies, determining everything from how often their blood work is monitored to when dialysis is initiated. For example, switching to the 2021 equation for estimating kidney function would mean 1 in every 4 patients with current eGFR less than 15 ml/min per 1.73 m2 would have blood work drawn every two months, instead of monthly.
When the researchers looked at the outcomes of patients over a two-year period, it did appear that the 2021 equation was more predictive of who went on to dialysis. However, more research – and particularly a prospective study with a gold standard comparison group – is needed to understand which equation is truly more accurate.
“Both equations are just estimates,” Atiquzzaman emphasizes. “Before we suggest province-wide implementation of the newer equation, we need a future study that uses the gold standard to measure the eGFR, and then we can say which equation is closer to the truth.”
