CT angiogram or calcium score: which and when

The calcium score and the CT coronary angiogram are cousins, and people often confuse them, but they answer different questions.

A calcium score is the simpler of the two: a low-dose scan with no injection that measures calcified plaque and gives you a risk number. It is the right first step when the question is about risk, when you sit in a grey zone and want to know whether to act.

A CT coronary angiogram, or CTCA, goes further. It uses a contrast dye injected into a vein to light up the coronary arteries in detail, showing not just calcium but soft plaque too, and whether any narrowing is significant. It is the right test when the question has moved on from risk to the arteries themselves: where symptoms suggest the flow might be limited, where a calcium score has come back high and you want to see what is going on, or where a doctor needs to rule out meaningful narrowing.

The trade is more than radiation. The CTCA involves a contrast injection and a higher dose than the calcium score, so it is kept for when the fuller picture is needed. It is good at ruling disease out, so a clean scan is reassuring. Where it finds a narrowing it is less certain, because a tight-looking narrowing on the scan proves significant only about half the time. That matters, because a positive finding can lead on to further tests, including an invasive angiogram, a fine catheter passed into the heart's own arteries, which carries its own small risks, and occasionally to a stent. Not every narrowing that shows up needs treating. So a finding can commit you to a pathway, and that is the part to weigh before the scan rather than after. Most people who want a heart look start with the calcium score, and only some need the CT angiogram at all.

Both are arranged with our imaging partners, and a doctor will talk through which one fits your question, and what each could lead to, before anything is booked. You decide how far to take it.

Ready to start? Choose the check that fits your question and tell us a little about yourself. A doctor reviews it, arranges what you need, and explains what it means. Most of it is done online, with the clinic there if you would rather be seen.