Millions of people check their cholesterol every year with a simple blood test, and doctors especially use the value of LDL, popularly known as “bad cholesterol”, to decide whether treatment is needed. But a new study by researchers at Northwestern Medicine suggests that this analysis may not give the whole picture of cardiovascular risk.
Another measurement, apolipoprotein B (apoB), could more accurately identify people who need more aggressive treatment to reduce the risk of heart attack and stroke.
LDL measures cholesterol, apoB counts the particles that carry it
Cholesterol is transported through the blood with the help of particles called lipoproteins. Some of these can contribute to the formation of atherosclerotic plaques, deposits that build up on artery walls and restrict blood flow.
Currently, doctors mainly use two values to assess risk: LDL cholesterol and non-HDL cholesterol.
LDL estimates the amount of cholesterol carried by particles considered atherogenic, while non-HDL includes several types of particles that can contribute to plaque build-up.
Apolipoprotein B (apoB) approaches the problem from a different perspective: it measures the number of particles that can cause these accumulations.
“Research strongly shows that apolipoprotein B is more effective in identifying people at risk because it counts the total number of harmful particles in the blood”explained Ciaran Kohli-Lynch, lead study author and assistant professor of preventive medicine at Northwestern University Feinberg School of Medicine.
In other words, two people can have the same LDL value, but a different number of apoB particles, and the cardiovascular risk can be different.
The study compared three methods of cholesterol assessment
Northwestern Medicine researchers published the analysis in the journal JAMA, using a computer model that simulated health outcomes for about 250,000 adults in the United States who were eligible for statin treatment but who did not already have cardiovascular disease.
The model compared three treatment decision strategies:
- using LDL cholesterol, with a target below 100 mg/dl;
- the use of non-HDL cholesterol, with a target below 118 mg/dl;
- using apoB, with a target below 78.7 mg/dl.
In scenarios where patients did not reach the goal, treatment was intensified by taking stronger statins and, if necessary, by adding the drug ezetimibe.
The researchers followed long-term the number of heart attacks, strokes, life expectancy, quality of life and medical costs.
The researchers’ conclusion was that the apoB-based strategy performed better than those based on LDL or non-HDL.
More heart attacks could be prevented with the same treatment strategy
According to the study authors, using apoB to guide treatment could prevent more cardiovascular events than current practice and would have a favorable cost-benefit ratio for medical systems.
A cardiologist explained what the normal cholesterol value is: “Below this threshold, atherosclerosis starts to regress”
“We found that testing apoB to boost cholesterol-lowering medication would prevent more heart attacks and strokes than current practice,” Kohli-Lynch said.
The researchers say this is the first large-scale analysis showing that using apoB to establish treatment is both medically and economically effective.
Why isn’t the apoB test done on a large scale already?
Although the evidence for the utility of apoB is growing, the test is not yet routinely used for most patients.
One reason is that the test usually requires an additional blood draw compared to standard cholesterol tests, which can mean higher costs for the patient.
“Our study asked the question: Is it worth spending extra money to use apoB instead of LDL to guide treatment intensification?”Kohli-Lynch said.
The researchers’ conclusion is that, in many situations, the additional information provided by apoB could justify these costs.
New cholesterol guidelines increase the importance of more accurate assessment
The study comes at a time when more cholesterol-lowering treatments are available to doctors than in the past.
Earlier this year, the American Heart Association and other medical organizations published updated guidelines on cholesterol management that emphasize earlier identification of people at high risk.
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For specialists, this development makes the question more important: how exactly are people identified who have the most to gain from intensive treatment?
If two people have the same LDL value, but one has more circulating apoB particles, the new type of analysis could give doctors a closer picture of the real risk.
What it means for patients
The new study doesn’t mean LDL testing becomes useless. LDL cholesterol remains an important indicator and is widely used in the assessment of cardiovascular risk.
The message from the researchers, however, is that LDL doesn’t always tell the whole story.
For certain people, especially those at high cardiovascular risk, with multiple risk factors, or with unclear results, measuring apoB may provide additional information to help the physician choose the right treatment.
The decision to do such a test or to change treatment should be made with the doctor, depending on each patient’s history and individual risk.
