Who really needs a coronary calcium scan?

The scan measures the amount of calcium in the walls of the coronary arteries. Calcium is a marker of atherosclerosis, the build-up of fatty plaque that can narrow arteries and lead to a heart attack. Unlike a CT coronary angiogram, a calcium score does not need contrast dye. It does involve a small dose of radiation, which is one reason it should only be done when the result is likely to be useful.

A score of zero means no calcium was seen. Higher numbers mean more calcified plaque and, in general, a higher risk of future heart attack or stroke. The scan does not show soft plaque that has not yet calcified, and it does not show whether an artery is narrowed, so a zero score does not rule out all heart disease and a high score does not mean a heart attack is inevitable.

Researchers at Northwestern University followed more than 6,000 adults in the United States, aged 45 to 79, for 10 years. Each person had a calcium scan and a standard risk estimate from PREVENT, the American Heart Association's risk calculator. Over the decade, 6% of them had a heart attack or stroke.

Across the whole group, adding the calcium score improved the risk prediction only slightly. The picture changed for people whose standard estimate put them in a borderline or intermediate risk range. For them, the scan gave a clearer indication of who was more likely, and who was less likely, to go on to have a heart attack or stroke.

The researchers also pointed out the downsides of scanning the wrong people. In people at low risk, routine scans may mean unnecessary radiation, further tests and cost without a clear benefit. In people at high risk, a statin is usually recommended whatever the scan shows. The study was carried out in the United States using an American risk calculator, so its findings may not translate exactly to the tools used in the UK.

In the UK, NICE recommends using the QRISK3 calculator to estimate a person's risk of heart attack or stroke over the next 10 years. It draws on information such as age, blood pressure, cholesterol, smoking and diabetes. Calcium scoring is not part of NICE's recommended routine risk assessment, and according to the British Heart Foundation it is currently used mainly in private practice.

European guidance takes a similar view. The European Society of Cardiology's prevention guidelines say calcium scoring may be considered to improve risk classification in selected people, rather than recommending it for everyone. In practice, that means the scan is most helpful when your risk sits close to the point where a decision about treatment, such as starting a statin, could go either way.

A calcium scan is unlikely to help if you are at clearly low risk, because the result is unlikely to change anything, or at clearly high risk, because treatment is usually recommended anyway. It adds little if you already have known coronary artery disease, have had a heart attack, or have had a stent or bypass surgery.

It is also not a test for symptoms. If you have chest pain, NICE recommends a different CT scan, a CT coronary angiogram with contrast dye, as the usual first test for suspected stable angina. Chest pain that is severe, lasts more than a few minutes, or comes with sweating, sickness or breathlessness needs urgent attention: call 999.

A calcium score refines risk; it does not replace a full assessment. A score of zero is reassuring but does not give lifelong protection, and a high score is a reason to take risk factors seriously rather than a reason to panic. Stopping smoking, controlling blood pressure and cholesterol, staying active and eating well remain the foundations of prevention, whatever the scan shows.

At The Cardiology Clinic, a cardiac risk assessment can help decide whether a calcium scan would add anything in your case, and Dr Khambekar can arrange one where it is likely to change your care. This article is general information and not a substitute for individual medical advice.

This article draws on a 2026 study by researchers at Northwestern University published in JAMA, NICE guidance on cardiovascular risk assessment and on the assessment of chest pain, the European Society of Cardiology guidelines on cardiovascular disease prevention, and British Heart Foundation information on CT scans of the heart.