Our approach to CT calcium score

In primary prevention, CT calcium scoring is sometimes useful in decision making surrounding statin use.

Some of the underlying concepts are somewhat complex and have been covered in our symposiums.

The screening paradigm remains that of matching the intensity of preventive efforts with the individual’s absolute risk.

The appropriateness of CT calcium scoring for an individual patient depends on

-       patient’s pretest probability of atherosclerotic cardiovascular disease

-       potential benefits of preventive therapies

-       negative aspects and risks of preventive therapies

-       patient preference

In many cases, “patient preference” is the main influencing factor in determining if CT calcium scoring is useful.

-       On one end of the spectrum, patients may be very risk averse and would prefer to be on preventive therapies despite lowish absolute risk of cardiovascular disease.

-       On the other end of the spectrum, patients may be very medication averse and would prefer NOT to be on preventive therapies despite highish absolute risk of cardiovascular disease

The probability of a non-zero CT calcium score is the critical parameter. it prompts clinicians and patients to carefully consider what to do with the CT calcium score results. From the predicted probabilities, one often arrives on a sensible primary prevention strategy without performing such test. In other situations, one may find the probabilities of needing treatment vs. not needing treatment as toss-up, which reinforces the need for the CT calcium score test.

To simply the process for everyone, here is our approach.

1. Use this simple calculator to calculate the probability of a non-zero CT calcium score and the predicted calcium score for an individual patient prior to the CT test, based on age, gender, and ethnicity alone, from the MESA cohort data.

2. If the non-zero score probability is close to 50%, the patient is likely to benefit from the calcium score test, as it essentially says that there is a 50% chance that statins would not be needed.

3. If the non-zero score is close to 80-100%, the patient is unlikely to benefit from the calcium score test, as coronary artery disease is likely present, and one should be aggressive with primary prevention, including statins. Functional tests. such as exercise treadmill should be used, if there is any hint of cardiac sounding symptoms.

4. If the non-zero score probability is close to 0-20%, the patient is also unlikely to benefit from the calcium score test. Many scans would be performed for each positive scan, potentially exposing patients to unnecessary radiation risk. Of note, young patients may not have time to develop calcium in their coronary arteries, hence, false negative calcium score test is likely despite high their lifetime cardiovascular risk. (Case example: 20F with familial hypercholesterolaemia would almost certainly have a zero calcium score, but has very high lifetime cardiovascular risk.)

5. You could adjust the probabilities based on how strong the family history is, and whether there are other risk factors (e.g. diabetes). Family history should take into account the age of onset of the coronary artery disease. Usually the odds ratio for diabetes is around 2.0.

Feel free to contact to team @ Cardiology Institute if you have specific queries about your individual patients.

As further case examples, try considering these scenarios using the calculator and decision algorithm above

(a) 65M, Caucasian, who is risk averse, and would like statins unless he has a calcium score of 0;

(b) 45F, Chinese, who is treatment averse, and would not want to be on a statin if at all possible.

Author: Dr Andrew To