CAC vs CTCA: which heart scan should you have, and what happens with the result?
A coronary calcium score (CAC) and a CT coronary angiogram (CTCA) can both show whether plaque is building in your heart’s arteries. They see different things — and the scan matters less than what your doctor does with the result.
Most people who ask us about a heart scan have no symptoms at all. They have a parent who had a heart attack in their fifties, or cholesterol that has crept up, or a raised Lp(a) on a recent screen. They want to know one thing: is plaque building up in my arteries?
There are two CT scans that can answer that, and they see different things. A coronary calcium score (CAC) is a quick scan without contrast dye that picks up hardened, calcified plaque. A CT coronary angiogram (CTCA) uses contrast dye to show both calcified plaque and the soft plaque that has not yet hardened, along with how narrowed each artery is.
At Advantage Medical Group in Singapore, a CAC score costs $360 and a CTCA $1,220, before GST. If you are not sure which to have, a consultation with one of our doctors is the place to start. For most people we recommend a CTCA, because a normal calcium score does not rule out soft plaque.
But the scan is not the end point. Under the 2026 ACC/AHA cholesterol guideline, your scan result can be used to set a personalised target for your LDL cholesterol — the more plaque the scan shows, the lower the target. Your doctor can use your result to set that target, alongside everything else we know about your risk.
If you have chest pain or get breathless on exertion, a screening scan may not be the right first test. Please see a doctor for a proper review first.
- A calcium score only sees calcified plaque. A score of zero is good news, but it does not rule out soft plaque — which turned up in about one in ten people with a zero score, in a pooled analysis of 37,808 people without symptoms.
- A CTCA shows calcified and soft plaque, how severe any narrowing is, and whether the plaque has features linked to later heart attacks.
- Under the 2026 ACC/AHA guideline, a calcium score sets an LDL target: below 2.6 mmol/L for a score of 1–99, below 1.8 for 100–299, and below 1.4 for 1,000 and above. For 300–999, where the guideline gives no target, our doctors use below 1.8 mmol/L.
- The guideline also recommends measuring lipoprotein(a) at least once in every adult.
- Neither scan is a test for chest pain. Symptoms need a test of how the heart copes under stress.
What a calcium score shows
Think of a calcium score as a single snapshot of any calcium sitting in the walls of your heart’s arteries. It is a plain CT scan, with no dye and no needle, and it turns what it finds into a number called the Agatston score. Zero means no calcium was seen. The higher the number, the more there is.
It works because calcium shows up brightly on CT. The catch is that soft tissue does not. Plaque starts soft and only calcifies over time, so a calcium score sees the older, hardened plaque well and cannot see the newer, soft plaque at all.
That still makes a zero score genuinely useful. In people being investigated for stable chest pain, a calcium score of zero ruled out a narrowing of 50% or more in 98.1% of cases. Most of the time, a zero can be trusted.
What a zero cannot tell you is that there is no plaque at all. A recent review pooled 37,808 people without symptoms who all had a calcium score of zero. When they went on to have a CT coronary angiogram, about 10% had soft plaque — and in the studies that measured it, about 1.1% had soft plaque that was already narrowing an artery significantly.
None of this makes a calcium score a bad test. It is a limit of what it is built to see. A calcium score answers one question well — how much calcified plaque is there — and it does so quickly and at a much lower cost.
What a CT coronary angiogram shows
A CTCA goes further. A contrast dye is injected into a vein in your arm, and as it flows through the heart’s arteries, the scanner can see both the channel the blood travels through and the wall around it. That means it picks up soft plaque as well as calcified plaque, and shows exactly how narrowed each artery is.
It can also show us what the plaque looks like — and that matters. Some plaque has features that tend to come before a heart attack: a low-density core, a wall bulging outwards, a ring-like appearance, small flecks of calcium. When researchers looked back at plaques that later caused a heart attack, these features had been visible on CT beforehand.
The SCOT-HEART trial found that soft, low-density plaque seen on CTCA predicted later heart attacks more strongly than standard risk scores, the calcium score, or how narrowed the arteries were. In other words, the type of plaque tells us something the amount alone does not.
A CTCA is a more involved test, and it is fair to know that upfront. It needs the contrast dye, carries a higher radiation dose than a calcium score, and usually needs a tablet to slow your heart rate so the images come out clearly. Overall it takes about 10–30 minutes longer. And because the dye is cleared through the kidneys, our usual practice is to check your kidney function with a blood test from within the last 30 days before the scan.
Which scan we usually recommend, and why a calcium score still has a place
For most people, our doctors recommend a CTCA, because it can see the soft plaque that a calcium score cannot. It also shows us where the plaque is. If a CTCA finds narrowing in several segments of the arteries, or in a critical spot, that can be a reason to see a cardiologist even when you feel perfectly well. A calcium score cannot show any of this — it tells us how much calcium there is, not where the narrowing sits or how severe it is.
A calcium score still has a real place, and it is usually far better than having no test at all. Here is why. Take someone with no symptoms whose LDL cholesterol comes back at 2.9 mmol/L. On a standard blood test, that might look acceptable. But if a calcium score then came back at, say, 150, the 2026 guideline would put their LDL target below 1.8 mmol/L — a very different conversation. Without the scan, nobody would know.
At $360 against $1,220 before GST, with no dye involved, a calcium score is a sound test within the limits above. If cost matters, it is a reasonable choice. The right scan depends on your risk factors and on what the result would change, which is exactly the conversation to have with your doctor.
What happens with the result: a personalised LDL target
This is the part that changed this year. The 2026 ACC/AHA guideline on managing cholesterol, published on 13 March 2026, replaced the 2018 guideline. One of its changes is to use your calcium score to set your LDL cholesterol target, if your scan shows plaque.
The idea is simple: the more plaque you already have, the lower your LDL should be.
| Calcium score | LDL target | Where it comes from |
|---|---|---|
| 0 | No target set by the scan | — |
| 1–99 | Below 2.6 mmol/L | 2026 ACC/AHA guideline |
| 100–299 | Below 1.8 mmol/L | 2026 ACC/AHA guideline |
| 300–999 | Below 1.8 mmol/L | AMG clinical practice |
| 1,000 and above | Below 1.4 mmol/L | 2026 ACC/AHA guideline |
You may notice a gap. The guideline sets no target for scores between 300 and 999. For that range, our doctors use below 1.8 mmol/L. That is our clinical practice, not the guideline’s.
The guideline also uses a target of below 1.8 mmol/L if your score is at or above the 75th percentile for your age and sex, even when the number itself is under 100.
Your doctor can use your scan result to set your personalised target, and will talk it through with you alongside your blood pressure, blood sugar, family history and Lp(a). A score of zero means the scan itself does not set a target — but your other results still count.
How to reach your target is a conversation for your consultation. This article explains the thinking behind it; it is not a treatment plan.
Why Lp(a) belongs in the same conversation
The 2026 guideline recommends measuring lipoprotein(a) — Lp(a) — at least once in every adult. Lp(a) is mostly inherited and stays much the same throughout life, so for most people one test is enough. A raised Lp(a) is one of the things your doctor weighs up when setting your target. Our article on Lp(a) explains what it is and what your result means. If heart disease runs in your family, see screening for family history.
Who the guideline suggests scanning
The 2026 guideline suggests considering a calcium score for men over 40 and women over 45 whose 10-year risk of heart disease is borderline or intermediate — where the result would help decide on treatment. That is the guideline’s position. Whether a scan makes sense for you depends on your own risk factors, and that is a question for your doctor.
If you have symptoms, you need a different kind of test
Neither a calcium score nor a CTCA is a test for chest pain. If you get chest pain, tightness, or breathlessness when you exert yourself, what matters is whether your heart is getting enough blood when it is working hard. That needs a different kind of test — such as an exercise ECG, a stress echocardiogram, a stress MRI, or an invasive angiogram. Scans like CAC and CTCA show the structure of the arteries; stress tests show how well blood flows through them. They answer different questions. If you have symptoms, please see a doctor promptly rather than booking a screening scan.
It works the other way too. Passing a treadmill stress test tells you there is no narrowing severe enough to restrict blood flow — usually more than 70%. It does not tell you there is no plaque. It is quite possible to pass a stress test and still have a fair amount of plaque that simply has not narrowed the artery yet.
How one scan changed a treatment plan
A man in his sixties came in for a health screen. He had no chest pain, no breathlessness and no family history of heart disease, and he had never smoked. He was overweight, his LDL cholesterol was around 3.2 mmol/L, and his blood sugar had been creeping up, though never far enough to be diagnosed or treated.
He had recently passed a treadmill stress test — his heart handled the exercise normally. As part of his screen at AMG, he chose to have a CT coronary angiogram after discussion with our doctors due to his underlying risk factors.
The scan found a calcium score of over 400, with calcification across several arteries. None of the narrowing was more than 50% — not enough to restrict blood flow during exercise, which is why the stress test was normal. But it showed that plaque had been building quietly for years.
That changed the plan. On its own, an LDL of 3.2 might simply be watched. With the scan result, his doctor started lipid-lowering treatment with a specific target: LDL below 1.8 mmol/L, the target our doctors use for a calcium score in his range. A follow-up scan was planned to check the plaque stays stable.
The stress test and the scan were both right. The stress test looked for narrowing severe enough to limit blood flow, and found none. The scan looked for plaque, and found it. They answer different questions.
Anonymised case story; individual outcomes vary. General information, not medical advice.
Find out what your arteries show — and what to do about it
Our doctors look at your risk factors, advise which scan suits you, and use the result to set your personalised targets. We see patients at Bukit Timah, Marine Parade and Jurong West.
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References
- Blumenthal RS, Morris PB, Gaudino M, et al. 2026 ACC/AHA/AACVPR/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Dyslipidemia. J Am Coll Cardiol. 2026;87(19):2624–2757.
- Williams MC et al. Low-Attenuation Noncalcified Plaque on Coronary Computed Tomography Angiography Predicts Myocardial Infarction: Results From the Multicenter SCOT-HEART Trial. Circulation. 2020;141(18):1452–1462.
- Motoyama S et al. Computed tomographic angiography characteristics of atherosclerotic plaques subsequently resulting in acute coronary syndrome. J Am Coll Cardiol. 2009;54(1):49–57.
- Sama C, Abdelhaleem A, Velu D, et al. Non-calcified plaque in asymptomatic patients with zero coronary artery calcium score: A systematic review and meta-analysis. J Cardiovasc Comput Tomogr. 2024;18(1):43–49.
- Wang X et al. A zero coronary artery calcium score in patients with stable chest pain is associated with a good prognosis, despite risk of non-calcified plaques. Open Heart. 2019;6(1):e000945.
Educational content. Not medical advice. Please discuss any health concerns with your doctor.