Emory study shows new type
of kidney function test is faster, easier and more precise than traditional
method
Determining how well a patient's
kidneys are functioning is a key part of evaluating various urological
conditions. But this can be a cumbersome task, since the traditional
method of measuring kidney function requires patients to collect their
own urine over a 24-hour period.
Emory urology researchers
say a new type of kidney test is more precise than the traditional 24-hour
creatinine clearance method - and it only takes five minutes.
In a study to be presented
Sunday, April 30, at the American Urological Association's 95th Annual
Meeting in Atlanta, the researchers compared the effectiveness of evaluating
kidney function via the MAG3 nuclear renal scan versus the traditional
method of urine creatinine clearance.
The nuclear scan involves
injecting a solution of MAG3 into the bloodstream. MAG3, short for mercaptoacetyltriglycine,
is a small group of amino acids "labeled" with a radioactive isotope
of the element technetium, commonly used in medical tests. This radioactive
marker allows doctors using a gamma camera to track the solution of
MAG3 as it progresses through the body.
"One can see it as it enters
the kidney, goes through the kidney and then drains into the bladder,"
explained Emory radiology professor Andrew Taylor, M.D., who designed
the study. Taylor is co-director of nuclear medicine at Emory.
The 24-hour creatinine clearance
method measures the level of the protein creatinine in urine. Normal
kidneys filter creatinine out of urine; thus, its presence in urine
indicates a possible problem. By determining the amount of creatinine
in the urine, doctors can calculate kidney function.
The latter method can be
an ordeal for the patient, who must collect and refrigerate the urine
samples before rushing them to the hospital for analysis. The samples
can be easily contaminated, invalidating the results.
"The MAG3 scan is much more
pleasant to the patient," said Emory urologist Muta Issa, M.D. Issa
is chief of urology at the Veterans Affairs Medical Center in Atlanta.
The study showed the MAG3
scan also is more precise than creatinine clearance in terms of evaluating
changes in kidney function over time, an important aspect of monitoring
patients.
"With renal function, it's
often important to know whether it's stable, getting worse or getting
better," Dr. Taylor said. "If it's getting worse, that indicates the
need for a change in therapy."
Researchers concluded that
the MAG3 scan may be a superior method for measuring sequential renal
function.
The study was supported by
Mallinckrodt Medical Inc., a medical equipment company specializing
in imaging.
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