Heart attack risk: Is expanded cholesterol testing warranted?

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Some specialists say screening is needed to detect ‘bad cholesterol’ linked to heart attacks in younger people, but the RACGP is cautious.

Current standard cholesterol testing does not include lipoprotein(a).

Heart disease experts recently called for wider testing of lipoprotein(a) – or Lp(a) – the ‘bad cholesterol’ thought to lead to sudden heart attacks in younger people, warning that an estimated 20% of Australians may have mild or high levels but may not be aware of them.

Elevated levels of Lp(a) have been shown to increase the risk of the inherited genetic condition atherosclerosis which causes hardening of the arteries. In addition to some lifestyle factors, increased levels are mainly due to genetic variations in the LPA gene, while the other ‘bad’ cholesterol, low-density lipoprotein, is linked to lifestyle factors.

These factors lead to calls for expanded screening, with the Royal College of Pathologists of Australasia making a submission to the Medical Services Advisory Committee (MSAC) for Medicare funding of Lp(a) testing as an independent predictor of cardiovascular disease (CVD) .

However, the RACGP does not support the application for Lp(a) testing at this stage, saying more evidence is needed to justify its benefits becoming part of standard practice.

In an October 2022 submission to MSAC, the college states that several risk modifiers will be included in the revised Australian CVD Risk Calculator that have ‘significant overlap’ with indications for Lp(a) testing, making the proposed test ‘redundant ‘ make.

Instead, the RACGP recommends that the new draft Australian CVD Risk Calculator should form the basis of screening.

Professor Mark Morgan, chair of RACGP Expert Committee – Quality Care, believes there is a need for caution to avoid ‘confusion or implied recommendation’ for Lp(a) testing.

“There is a big difference between population screening activities and the clinical effects of selected patients who are at particularly high risk,” he told newsGP.

Using examples of population screening, including mammography and FOBT for bowel cancer, Professor Morgan cites the World Health Organization’s (WHO) version of Wilson and Jungner’s principles of screening, recommending that there should be a recognizable ‘latent or early symptomatic’ phase be and an accepted treatment’ for patients with recognized disease.

“These principles effectively state that Lp(a) screening should only be considered if there is proven beneficial treatment available for abnormal results detected by the screen,” he said.

‘Much remains to be learned about the biology of Lp(a) and the genetics that underlie the biology.

‘PCSK9 [Proprotein convertase subtilisin/kexin type 9] Inhibitors have been shown to reduce Lp(a) levels, but it is not clear where they fit in primary prevention of patients’ first cardiovascular event.’

Currently, Medicare does not cover any of the costs of Lp(a) testing. However, experts calling for testing expansion say patients with a family history of early heart disease, those who have had multiple heart attacks or strokes despite treatment, and people who developed heart disease before age 65 should receive subsidized access.

Speaking to The Age, Professor Jason Kovacic, Executive Director at the Victor Chang Cardiac Research Institute, said it was important to raise awareness of the risks of elevated Lp(a) and increase access to testing.

“We have long wondered why healthy people with low cholesterol levels and seemingly no other major risk factors such as smoking or diabetes can have heart attacks,” he said.

‘But we now understand that high levels of Lp(a) may be responsible for many of these events.’

Professor Morgan says these comments highlight a subset of people who have high Lp(a) as an ‘often inherited’ risk factor.

“There will need to be an application of WHO screening principles and some modeling to determine whether there should be a screening program for this inherited risk factor,” Professor Morgan said.

“It would be wrong to jump in with ad hoc opportunistic testing without examining harms, costs and benefits of new treatments.”

Professor of General Practice at the University of Tasmania Mark Nelson, who has led extensive research into statins, agrees that although GPs should be aware of the risks of high Lp(a) levels and to consider treating people who show any symptoms , to test, more evidence is needed before extensive screening is introduced.

“There is good evidence for Lp(a) as a significant risk factor,” he told newsGP.

‘However, this is not standard selection or rebate as such. The critical thing at the moment is for GPs to adopt risk algorithms and treat accordingly.’

Professor Nelson recommends following the new algorithm included in the updated guidelines for the management of absolute cardiovascular disease risk, which will be released this year.

Appropriate screening principles and further modeling are needed to determine whether screening for Lp(a) should become standard, says Professor Mark Morgan, expert in quality care.

The RACGP Red Book, which is being revised ahead of the release of its 10th edition, states that absolute CVD risk assessment should be carried out ‘at least every two years’ in all adults over 45 years (> 35 years for Aboriginal and Torres Strait Islander) Islanders) who are not known to have CVD or to be at ‘clinically determined high risk’, by the patient’s:

age gender smoking status total and high-density lipoprotein cholesterol systolic blood pressure other existing conditions.

“In adults with a low absolute CVD risk, blood test results can be used for revision of absolute CVD risk within five years, unless there are reasons to the contrary,” the Red Book states.

It also identifies that ‘increased frequency and early onset’ of premature ischemic heart disease or sudden cardiac death ‘may suggest’ the presence of genetically determined diseases.

Professor Morgan says that along with the updated Red Book, GPs should await the updated version of the CVD risk guidelines to see if there is a recommendation to check Lp(a), but he stresses that equivalent international guidelines do not currently recommend the test not.

“For people in their 40s to 70s who don’t have medical history that immediately puts them in a high-risk category, there will be an updated risk tool that is expected to be better able to assign a risk category to inform preventive lifestyle and treatments. than the existing absolute cardiovascular risk calculator,’ he said.

“For people who have a strong family history of premature heart disease and high cholesterol levels, there is a need to consider familial hypercholesterolemia, which is underdiagnosed and undertreated.”

The RACGP’s Genomics in General Practice also includes guidance on screening and clinical decision-making for familial hypercholesterolaemia.

Until further clinical updates and evidence emerge, Professor Morgan advises that further research supporting Lp(a) testing is needed.

“In the 2021 scientific statement from the American Heart Foundation, it is clear that there are significant priority areas for more research,” he said.

‘The statement emphasized that the reference ranges and tests for Lp(a) are not standardized and that there is a poorly established impact of ethnicity on Lp(a) levels which is a priority for further research.

‘Before doing any test, it’s worth asking: “How will the test change my driving recommendations?”

‘For Lp(a) this question has not been clearly answered.’

cholesterol levels CVD risk heart attack lipoprotein (a) preventive care

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