New Tests Could Spot Which Kidney Patients Will Do the Worst

MONDAY, April 11, 2011 (HealthDay News) -- Researchers have come up with two new tests that seem better able to predict which patients with chronic kidney disease are more likely to progress to kidney failure and death.

This could help streamline care, getting those patients who need it most the care they need, while perhaps sparing other patients unnecessary interventions.

"The new markers provide us with an opportunity to address kidney disease prior to its terminal stage," said Dr. Ernesto P. Molmenti, vice chairman of surgery and director of the transplant program at the North Shore-Long Island Jewish Health System in Manhasset, N.Y. "Such early treatment could provide for increased survival, as well as enhanced quality of life."

"The main problem right now is the tests we use currently just are not very good at identifying people's progressing to either more advanced kidney disease or end-stage kidney disease, so this has big implications in trying to determine who will progress," said Dr. Troy Plumb, interim chief of nephrology at the University of Nebraska Medical Center in Omaha.

But, he added, "there are going to have to be validated clinical trials" before these new tests are introduced into clinical practice.

Both studies will appear in the April 20 issue of the Journal of the American Medical Association, but were released Monday to coincide with presentations at the World Congress of Nephrology, in Vancouver.

Some 23 million people in the United States have chronic kidney disease, which can often progress to kidney failure (making dialysis or a transplant necessary), and even death. But experts have no really good way to predict who will progress to more serious disease or when.

Right now, kidney function, or glomerular filtration rate (GFR), is based on measuring blood levels of creatinine, a waste product that is normally removed from the body by the kidneys.

The first set of study authors, from the San Francisco VA Medical Center, added two other measurements to the mix: GFR measured by cystatin C, a protein also eliminated from the body by the kidneys; and albuminuria, or too much protein in the urine.

They then compared the three markers together with the current standard of creatinine-based GFR alone.

Indeed, combining the three markers more accurately predicted which of 26,643 patients were more likely to progress to kidney failure and death.

The next best predictor for end-stage renal disease was cystatin C plus albuminuria. And, in fact, various organizations have already been lobbying for new guidelines that would add albuminuria to testing protocols. The current standard was introduced in 2002.

For the second study, researchers from Tufts Medical Center in Boston combined data from several commonplace lab tests to come up with a model that accurately predicted the short-term risk of kidney failure (needing dialysis or a transplant) in people who already had moderate-to-severe kidney disease.

Overall, the test was developed and confirmed in two groups of Canadian patients totaling nearly 8,500 men and women with kidney disease.

A model that took into account the eight variables -- age, sex, estimated GFR, albuminuria as well as blood levels of calcium, phosphate, bicarbonate and albumin -- was more accurate than a four-factor model, which only took into account age, sex, GFR and albuminuria.

The authors were excited enough by the findings that they have already developed an online calculator and smart phone application so doctors can use the model in practice, said study author Dr. Navdeep Tangri.

"These are lab tests that are collected on every doctor's visit, so it's broadly applicable," he said. "We're gearing up for wider use."

But, an accompanying editorial urged caution in immediately implementing the tests without further validation.

Plumb also noted that the test developed by Tangri's team would be easier to implement because it relies on regularly done tests, while a cystatin C test is not readily available and usually needs to be sent out for analysis.

More information

The National Kidney Foundation has more on chronic kidney disease.