Rapid blood test could speed up myocardial infarction diagnosisBMJ 2017; 358 doi: https://doi.org/10.1136/bmj.j4502 (Published 27 September 2017) Cite this as: BMJ 2017;358:j4502
A new blood test could potentially help to rule out myocardial infarction more quickly than the current troponin tests, finds a study in Circulation.1
The new test analyses concentrations of a biomarker called cardiac myosin binding protein C (cMyC). Concentrations of this protein increase more rapidly after a myocardial infarction and to a higher extent than troponin, which means the test could potentially rule out myocardial infarction in a higher proportion of patients straight away.
Over two thirds of people who attend hospital emergency departments with chest pain have not had a myocardial infarction. The UK researchers said that this new biomarker could mean such patients could be sent home more quickly, so freeing up beds and saving the NHS money.
Currently patients suspected of having a myocardial infarction are assessed by electrocardiogram (ECG) and a blood test to measure high troponin concentrations, which is repeated after three hours. The National Institute for Care and Health Excellence issued guidance in 2016 recommending that all patients with acute chest pain who are assessed as being at medium or high risk of a myocardial infarction be given the newer high sensitivity troponin blood tests rather than standard troponin tests.23 Depending on the type of troponin test used, up to 85% of people will need to remain in hospital for further tests to rule out a myocardial infarction.
The latest study, funded by the British Heart Foundation, included 1954 unselected patients with acute chest pain presenting to emergency departments in nine hospitals around Europe. The median age of the patients was 62 years, 31% were women, and 36% had a prior history of coronary artery disease. Concentrations of cMyC and high and standard sensitivity cardiac troponins were measured at presentation.
An acute myocardial infarction was diagnosed in 340 (17%) of the patients. The diagnostic accuracy of the cMyC test was similar to that of the standard and sensitive troponin tests in the entire cohort. But it was found to be superior to troponin tests in giving the all clear to patients who presented within the first three hours of experiencing chest pain.
The cMyC test correctly triaged more patients to “rule out” or “rule in” groups than either troponin test, leaving a much smaller proportion who needed to remain in an observation group. The cMyC test correctly classified 443 patients (32.4%) as not having a myocardial infarction (ruled out), whereas the high sensitivity troponin test ruled out 348 (25.4%) and the standard troponin test 206 (15.1%).
Tom Kaier, one of the lead researchers, funded by the British Heart Foundation at St Thomas’ Hospital, London, said, “Our research shows that the new test has the potential to reassure many thousands more patients with a single test, improving their experience and freeing up valuable hospital beds in A&E departments and wards across the country.”
Mike Marber, professor of cardiology at King’s College London and head of the UK side of the research, said, “We’ve shown that this test is not only just as good as the current test for working out who has had a heart attack, but it’s also much better at working out who hasn’t.
“We would love to see this new test rolled out in hospitals in the next five years.”