Could a blood test predict heart risk?

A blood test could predict stroke and MI risk in CHD patients. Sanjay Tanday Reports

Levels of protein NT-proBNP increase when the heart is under stress
Levels of protein NT-proBNP increase when the heart is under stress

What is the story?

A simple blood test has been developed that could accurately predict a heart patient's risk of serious illness or death, according to media reports.

US researchers designed the blood test after finding that men and women with high levels of the amino terminal fragment of the prohormone brain-type natriuretic peptide (NT-proBNP) in their blood were more likely to suffer a heart attack, stroke or heart failure and were at a greater risk of dying than those with low levels.

The amount of the protein NT-proBNP indicates levels of a hormone known as brain type natriuretic peptide (BNP). When the heart wall over-expands because of high blood volume, or is damaged by lack of blood flow to the heart, levels of BNP increase along with the levels of NT-proBNP.

The papers said that those with the highest levels of NT-proBNP were almost eight times more at risk of having a cardiovascular event or dying than those with the lowest levels. 

What is the research?

The reports are based on a US researched paper that assessed the association of plasma NT-pro-BNP levels with subsequent cardiovascular events and mortality in 804 men and 183 women, with stable CHD.

To determine the value of NT-proBNP as an independent predictor of cardiovascular outcomes, other traditional risk factors including systolic and diastolic dysfunction and exercise capacity were adjusted for.A blood sample was provided by each patient and was tested for NT-proBNP levels using an immunoassay.

Medical history and smoking status were determined by a questionnaire and creatinine clearance was calculated from urine samples.Patients were then divided into four quartiles depending on their NT-proBNP levels and they were followed for an average of 3.7 years.

Annual telephone interviews were conducted with the participants, who were asked about any hospitalisation for heart trouble.

A total of 26 per cent of patients died or were hospitalised with a cardiovascular event during the study.

Those in the highest quartile were more likely to have clinical risk factors for adverse cardiovascular events, including a history of hypertension and lower creatinine clearance, than those in the lowest quartile.

The researchers found that each increasing quartile was associated with a greater risk of cardiovascular events or death. Patients in the quartile with the highest levels of NT-proBNP with levels greater than 460pg/ml, were eight times more likely to die or have a cardiovascular event than the patients in the group with the lowest levels, 8.06-73.95 pg/ml.

What do the researchers say?

Lead researcher Dr Mary Whooley, associate professor of medicine at the University of California, San Francisco, said: ‘The NT-proBNP marker is picking up something that could not be detected with standard tests like echocardiography.'

However, Dr Whooley warned that the test should only be used on patients who were known to have heart disease, as using it on every patient would lead to more false positive results than true positive results.

The test might be of limited value because patients at risk of cardiovascular disease will be using medicines to prevent cardiovascular events, she said.

‘The best the test can do is to help identify patients for more aggressive therapy.'

What do researchers say?

Kent GP Dr Rubin Minhas, CHD lead for Medway PCT, said that the development of a blood test to detect BNP wanot new and he used a different test.

‘We know that increases in BNP levels are associated with a greater risk of cardiac events. We have been measuring patients' BNP levels here in Medway.'

More research needed to be done to attach practical significance to these findings, he said.

Joe Korner, director of communications at the charity Stroke Association, welcomed the news of the blood test saying that it was a valuable tool to help identify the risk of having a stroke. He added that a high BP remained the biggest risk for stroke and CHD patients should have regular BP checks.

  • A blood test has been developed to detect the levels of the protein NT-proBNP in patients with CHD.
  • NT-proBNP levels increase when the heart is under stress.
  • Those with the highest levels of NT-proBNP were eight times more at risk of cardiovascular events than those with the lowest levels
  •  The value of the blood test has been questioned.

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