Glomerular filtration rate (GRF) is a test used to determine whether the kidneys are functioning properly and is used in the diagnosis of chronic kidney disease (CKD). In addition, GRF is an independent predictor of all-cause and cardiovascular mortality and renal failure. According to clinical guidelines, physicians are advised to report estimated GFR when measuring serum creatinine levels.

The researchers said:

"The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation more accurately estimates GFR than the Modification of Diet in Renal Disease (MDRD) Study equation using the same variables [age, sex, race, and serum creatinine level], especially at higher GFR, but definitive evidence of its risk implications in diverse settings is lacking."

In order to assess if estimated GFR calculated by the CKD-EPI equation predicts risk for adverse outcomes more accurately than the MDRD Study equation in a broad range of populations, Kunihiro Matsushita, M.D., Ph.D., of the Johns Hopkins University, Baltimore, and colleagues conducted a meta-analysis using data from 13 CKD cohorts, 25 general population cohorts, and 7 high-risk cohorts (of vascular disease).

The researchers examined data from 1.1 million individuals aged 18+ from 40 countries or regions of Asia, North America and South America, Europe, Oceania, and the Middle East. Data transfer and analyses were carried out between March 2011 and March 2012.

The primary adverse outcomes the researchers examined were:

• end-stage renal disease (ESRD) (7,644 events from 21 cohorts)
• all-cause mortality (84,482 deaths from 40 cohorts
• cardiovascular mortality (22,176 events from 28 cohorts)

Furthermore, the the researchers found that around 0.6% of patients were reclassified to a lower category. Participants who were reclassified to a lower category (0.7%) had a higher risk of mortality and ESRD than patients who were not reclassified even after adjusting for different factors, while those who were reclassified to a higher category had lower risks.

According to the researchers, the prevalence of CKD stages 3 to 5 (

The researchers explained:

"Net reclassification improvement based on estimated GFR categories was significantly positive for all outcomes. Net reclassification improvement was similarly positive in most subgroups defined by age (diabetes and hypertension. The results in the high-risk and CKD cohorts were largely consistent with the general population cohorts."

They conclude:

"Overall, the CKD-EPI creatinine-based equation more accurately classified individuals with respect to risk of mortality and ESRD compared with the MDRD Study equation.

Given more accurate GFR estimation, lower CKD prevalence estimates, and better risk categorization by the CKD-EPI equation without additional laboratory costs, its implementation for estimated GFR reporting could contribute to more efficient and targeted prevention and management of CKD-related outcomes."

In an associated report, Kamyar Kalantar-Zadeh, M.D., M.P.H., Ph.D., of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, Calif., and Alpesh N. Amin, M.D., M.B.A., of the University of California-Irvine Medical Center, explained that:

"Even though CKD staging using the more conservative CKD-EPI equation seems valid because it produces more meaningful risk profiles, it is premature to conclude that the ultimate tool for estimated GFR accuracy has been found."

They continue:

"An even more conservative and accurate equation may be developed eventually, perhaps by these same investigators who first developed and advocated the MDRD equation (that is still in use in many estimated GFR laboratory reports) and who have now advanced the CKD-EPI equation to replace its MDRD predecessor.

Some inherent limitations of the MDRD equation remain essentially unchanged in the CKD-EPI equation, in particular the reliance on creatinine as a single suboptimal filtration marker that not only is a close correlate of skeletal muscle mass but also probably varies with the magnitude of ingested meat and nutritional status.

To date no single circulating biomarker meets the desired criteria of the ideal renal filtration marker. It is possible that a panel of several filtration markers, including cystatin C, for instance, combined with some surrogate markers of nutritional status and body composition, will provide a more accurate and clinically meaningful estimate of GFR."

Written By Grace Rattue
Copyright: Medical News Today
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