Time for change in CKD assessment, treatment

To improve the detection and management of the growing number of patients with chronic kidney disease, the formula commonly used for diagnosis and staging needs to be refined, according to a session at the American Society of Hypertension scientific meeting in Chicago last month.

"We need to address the issues of estimating glomerular filtration rate and quantifying albuminuria/proteinuria," said Matthew R. Weir, MD, one of the speakers and director of the division of nephrology at the University of Maryland School of Medicine in Baltimore.

Experts complained that the Modification of Diet in Renal Disease -- or MDRD -- formula used to estimate the GFR is not as accurate at the earlier stages of chronic kidney disease or for patients who are older. The tool is too reliant on creatinine, which can be affected by a person's size and muscle mass. The laboratory assays for this waste product are not standardized, although the issue is one on which the National Kidney Disease Education Program is working.

"It's very good for GFRs below 60, but there's a lot of imprecision in people with GFRs above 60," said Edgar R. Miller, MD, PhD, who also spoke at the session and is an associate professor of medicine in the division of general internal medicine at Johns Hopkins University in Baltimore.

A paper suggesting a revised formula incorporating cystatin C, an indicator of renal function, is expected to be published sometime over the next year or so, although many experts feel it will take far more than just one additional marker to improve the formula's utility.

"There has not been great confidence that cystatin C alone will improve estimating GFR, but it is being talked about," Dr. Miller said. "I'm sure cystatin C will be become part of an assessment."

On the management end, experts also are advocating treatment approaches, such as the use of angiotensin-converting enzyme inhibitors, that better protect the heart of these patients.

"The sicker the kidney, the greater the advantage of ACE inhibition," Dr. Weir said. "The kidney and the heart are very closely tied together by the same pipes, and it's clear that once that GFR starts to fall, the [cardiovascular disease] events increase. These are people who need global CVD risk reduction measures."

These medications often are used with hesitation as kidney disease progresses, although experts said they could be used safely if nonsteroidal anti-inflammatories and foods high in potassium were avoided.

"There's anxiety about treating people with higher creatinine with ACE inhibitors," Dr. Weir said. "It's not justified." He said his advice applied to most CKD patients except those who were in the end stages of their disease.