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Blood test can accurately diagnose
heart failure in patients with kidney dysfunction
NT-proBNP test results comparable
to those of BNP blood test in patients with kidney disease
BOSTON - December 14, 2005 - A large-scale analysis has shown
that a blood test previously found useful in diagnosing or ruling
out heart failure in emergency room patients remains effective in
patients with chronic kidney disease. The study also demonstrates
that the test for a marker called NT-proBNP can identify patients
at a higher risk for death, independent of kidney dysfunction. The
report from investigators at the Massachusetts General Hospital
(MGH) will appear in the January 3, 2006 Journal of the American
College of Cardiology and is receiving early online release.
"It is well understood that kidney disease reduces the usefulness
of testing for both NT-proBNP and a related biomarker called BNP,
and the conventional understanding was that NT-proBNP was the more
affected of the two," says James Januzzi Jr., MD, of the MGH
Cardiology Division, the paper's senior author. "However,
while kidney disease did lead to higher values of NT-proBNP in our
study, what really matters is clinical performance; and at optimal
cut-points, no matter how hard we looked, we found the relationship
between chronic kidney disease and the diagnostic accuracy of NT-proBNP
was no different than that of BNP. Our findings thus directly contradict
observations based on smaller, less characterized patient populations."
Congestive heart failure, which occurs when an impaired heart muscle
cannot pump blood efficiently, is a growing health problem and major
cause of cardiac death. The diagnosis of heart failure may be challenging
because its symptoms can overlap those of other conditions. Missing
a heart failure diagnosis can put patients at high risk of serious
problems, including death, but overdiagnosis may lead patients to
receive unnecessary treatment.
Published earlier this year, the
PRIDE study showed NT-proBNP to be highly sensitive and specific
for the diagnosis of acute heart failure in patients with shortness
of breath and to strongly predict patient deaths. A major concern
about the widespread use of the marker had been previous assertions
that kidney disease - very common in patients with heart failure
- might confound the results of NT-proBNP testing, since levels
of the marker were higher among those with reduced renal function.
Some researchers in the field argued that BNP was less affected
by chronic kidney disease than was NT-proBNP. "We found no
difference in our results when you examine them side-by-side with
those for BNP," says Januzzi. "When you consider the data
in totality, there just does not seem to be much difference between
these two markers with respect to their diagnostic usefulness in
patients with kidney disease. While kidney disease modestly reduces
the diagnostic accuracy of both markers, when used in the appropriate
manner, both tests appear to return identical information."
Besides the diagnostic value of NT-proBNP, the analysis evaluated
the prospective value of NT-proBNP testing for predicting death
within 60 days. "In fact, NT-proBNP measurement was an even
stronger predictor of death in breathless patients with significant
renal insufficiency, emphasizing the fact that the marker is likely
detecting a true signal of cardiac disease in these patients,"
said Januzzi, an assistant professor of Medicine at Harvard Medical
School. "This is a big step forward in the understanding of
the optimal application of NT-proBNP measurement, as it removes
one of the biggest obstacles that remained for the marker."
Co-authors of the study include first author Saif Anwaruddin, MD,
now a fellow in cardiology at the Cleveland Clinic Foundation; Aaron
Baggish, MD, Annabel Chen, MD, and Claudia Chae, MD, MPH, of MGH
Cardiology; Donald M. Lloyd-Jones, MD, MsC, Northwestern University;
Daniel Krauser, MD, New York Hospital; and Roderick Tung, MD, Cedars-Sinai
Hospital, Los Angeles. The study was supported by a grant from Roche
Diagnostics, which manufactures the NT-proBNP assay studied.
Massachusetts General Hospital, established in 1811, is the original
and largest teaching hospital of Harvard Medical School. The MGH
conducts the largest hospital-based research program in the United
States, with an annual research budget of nearly $500 million and
major research centers in AIDS, cardiovascular research, cancer,
cutaneous biology, medical imaging, neurodegenerative disorders,
transplantation biology and photomedicine. In 1994, MGH and Brigham
and Women's Hospital joined to form Partners HealthCare System,
an integrated health care delivery system comprising the two academic
medical centers, specialty and community hospitals, a network of
physician groups, and nonacute and home health services.
Media Contact: Sue
McGreevey, MGH Public Affairs
Physician Referral Service: 1-800-388-4644
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