Kidney Function: What to Do with an Isolated Finding of Low eGFR
Estimated glomerular filtration rate, or eGFR, measures kidney function based on a calculation utilizing serum creatinine, age and sex. Occasionally a lab panel results in an isolated finding of low eGFR. But does this result of a low eGFR, or a high creatinine result, really indicate kidney dysfunction? Perhaps not. CRL research suggests current underwriting guidelines may foster too much concern for a low eGFR because of the following:
- If the serum glucose is low (almost always from initial sample handling), the measured creatinine value may also be falsely elevated and needs to be adjusted downward thereby increasing the eGFR. Or, the sample needs to be tested using “enzymatic creatinine.” Click here for more details included in this On the Risk article.
- The now commonly used CKD-EPI method to calculate eGFR may generate values substantially lower than earlier methods including the Rule (Mayo Clinic) calculation, but some insurer cut-offs for rating eGFR have not been adjusted to reflect this change in algorithm. Click here to read more from this On the Risk article.
- Many eGFR guidelines and rating tables do not fully consider the progressive decline in eGFR seen in normal healthy individuals with aging. They may also be based on risk data where those with proteinuria or diabetes had not been excluded. Those combo situations are easy; what we need to know is if eGFR is an isolated finding. Click here to get more information from this On the Risk article.
We found that below age 50, isolated eGFR values less than 70 mL/min may have increased risk, but the risk cut-off decreases to as low as 60 mL/min for ages 50–69 and 50 mL/min for age 70+. At the older ages, values close to the cut-off may still fit within typical risk limits of a standard pool even if any preferred class is restricted.
Review the OTR articles linked above if you have a question about a lab result or rating based on eGFR, or if you have guidelines that may need updating. Contact ILSblog@crlcorp.com with any additional questions.
About the Author
Michael Fulks, MD, Consulting Medical Director, is board-certified in internal and insurance medicine. After leaving practice, he served as a medical director, creating or editing several underwriting manuals and preferred programs. For the past 13 years, Dr. Fulks has consulted for CRL, participating in its mortality research on individual tests and all laboratory test results, BP and build in combination. He is also involved in the development and implementation of automated screening tools for non-laboratory data.