New blood test to detect heart attack risk

Researchers, led by an Indian-origin scientist, have developed a new high-sensitivity blood test that could quickly identify patients at high risk of heart attack.
Using the blood test, researchers identified the optimal level of a protein called troponin that could rule out a diagnosis of heart attack for two-thirds of people attending the emergency department.
"Until now there were no quick ways to rule out a heart attack within the emergency department," said lead author Dr Anoop Shah from the University of Edinburgh in the UK.
"We have identified a cardiac troponin concentration (less than 5 nanograms per decilitre, 5 ng/L) below which patients are at very low risk of heart attack either during the admission or in the ensuing 30 days.

"These findings could dramatically reduce unnecessary hospital admissions and provide substantial cost savings for health-care providers," said Shah.
One of the most common causes of hospitalisation worldwide is acute chest pain. International guidelines recommend that individuals presenting with chest pain are admitted to hospital for testing for very high levels of troponin - a sign that a heart attack has occurred.

Current approaches for assessing patients with suspected heart attacks either require admission into hospital or lengthy stays in the emergency department for repeat testing.
Until now, whether new high-sensitivity cardiac troponin tests could identify very low-risk patients who may be suitable for immediate and safe discharge from the emergency department was unknown.

The test used in this study is more sensitive than the standard version and can detect far lower levels of troponin in the blood.
Using this test, troponin levels were measured in over 6,000 patients with chest pain admitted to four hospitals in Scotland and the US.
Shah and colleagues prospectively evaluated the negative predictive value (the probability that patients were not at risk) of heart attack or subsequent death from a heart condition after 30 days for a range of troponin concentrations.
The researchers found that a troponin threshold of 5 ng/L at presentation identified around two-thirds (61 per cent) of patients at very low risk of heart attack and may have been eligible for early, safe discharge - with a high negative predictive value of 99.6 per cent.

This high negative predictive value persisted irrespective of age, sex, cardiovascular risk factors, or prior cardiovascular disease, researchers said.
At one year, these patients had a three times lower risk of heart attack and cardiac death than those who had troponin levels 5 ng/L or higher.
The research was published in The Lancet journal.