Common metric may not accurately assess kidney function of Indian patients

A common metric for monitoring kidney health may not accurately represent the kidney function of Indian patients. However, tweaks to an older assessment formula may better measure kidney health in this patient population, according to new research presented today at the 2019 American Physiological Society (APS)/American Society of Nephrology (ASN) Conference, Control of Renal Function in Health and Disease in Charlottesville, Va.

Glomerular filtration rate (GFR) is a measure of how well the kidneys remove waste from the blood. It is used in clinical settings as an indicator of chronic kidney disease. The gold standard to measure GFR requires use of radioisotopes. Because of that, doctors usually test patients' blood for a waste product called creatinine and then enter those results into a formula with other factors such as age, sex and weight to determine an estimate of GFR. There are multiple formulae to estimate GFR, but the most common are based on data from Western populations.

Noting that many developing populations have higher fat-to-muscle tissue ratios for a given body mass index, researchers sought to determine the more accurate method to estimate GFR in Indians. They used the gold standard radioisotope method to measure GFR in 24 healthy Indian volunteers, 11 men and 13 women. They then evaluated different estimation formulae based on the radioisotope results. This included variations of the formulae using measures of lean mass in place of body weight. They determined lean mass via dual-energy X-ray absorptiometry (DEXA) scan. DEXA scans measure tissue density and are also commonly used to measure bone density and test for osteoporosis.

The researchers found the closest agreement to the radioisotope results came from the Cockcroft–Gault formula, with a substitution of lean mass in place of weight. The Cockcroft–Gault formula was developed in 1973 and is less used today than two newer formulae called the Chronic Kidney Disease Epidemiology Collaboration equation and the Modification of Diet in Renal Disease equation, neither of which provided results that were as accurate in this study as the modified Cockcroft–Gault formula.

The researchers note that a larger study is necessary to fully validate this method, especially considering the added use of a full-body scan. However, "use of body composition parameters for estimating GFR may improve clinical practice in Indian patients," they said.

Anjali Kulkarni, MD, of BARC Hospital in Mumbai, India, will present the poster "Improvement in estimates of GFR by using lean mass as compared to body weight in Indians: pilot study" on Tuesday, June 25, 2019, in Pavilion III of the Boar's Head Resort in Charlottesville, Va.