A blood test to predict a heart attack? Don’t hold your breath

    21 June 2016

    Headlines have claimed that a blood test can reveal the likelihood of a patient developing coronary heart disease in the next five years.

    The claim was based on a study published in EBioMedicine. Its key finding was that people with high levels of certain types of antibodies were less likely to have heart issues.

    Researchers at the National Heart and Lung Institute re-examined data from the monitoring of 1,753 subjects over five years. Those with the highest levels of immunoglobulin G were 58 per cent less likely to have a heart attack and 38 per cent were less likely to suffer from a stroke.

    Immunoglobulin levels were not previously considered an indicator of cardiovascular disease risk, but there is new evidence that they are linked to the risk of atherosclerosis, the build-up of fat in the arteries.

    Dr Ramzi Khamis, the study’s lead author, told the Independent: ‘This test, once confirmed in other studies as well, will significantly improve cardiac risk stratification.

    ‘As the current ways of determining risk are quite inaccurate, this means that more patients will be classified appropriately either at risk or not.

    ‘Therefore, hopefully fewer patients will be on treatment inappropriately and more patients who were missed in the past will be on appropriate treatment and monitoring.

    ‘If we can be better at selecting the right patients who need close monitoring and preventative therapies, we will for sure prevent heart disease leading to heart attacks.’

    Instant analysis
    Researchers re-examined data from the ASCOT study, which followed 19,000 people with high blood pressure, and, in a particular subgroup, compared those who developed a cardiac event with those who did not.

    Its focus — on people with high blood pressure — was specific and thus limits the potential to generalise about the wider population.

    Researchers sought to test the hypothesis that higher levels of antibodies — specifically immunoglobulin G and M anti-MDA-LDL antibodies — were associated with a lesser rate of cardiovascular events. In animal models, high levels of these markers have been linked to a lesser development of atherosclerosis (furring of the arteries).

    Researchers also looked at two other blood markers: CRP, a marker for inflammation and infection commonly, and NT-pro BNP, a hormone secreted in the heart when the heart is overloaded and overworked. 

    The data from the study does appear to show that a slightly higher level of IgG and IgM for anti-MDA-LDL was associated with a lower rate of cardiovascular event.

    However, there is a caveat: patients with inflammatory and rheumatological conditions would have elevated levels of these markers which would not preclude them from developing cardiovascular disease. 

    And, looking at the raw figures prior to the authors’ analysis, the differences (particularly in the serum samples) are small. I will not hold my breath for this to be transferred to general practice. I wonder, too, what extent laboratory error might have had an effect. Despite the researchers’ optimism, I think this is something for a fair few years into the future.

    The Q-Risk score is the test currently recommended by NICE to calculate the risk of a cardiovascular event in the next 10 years.
    Research score: 2/5