However, ordering CTs on younger, seemingly healthy individuals solely to get a CAC score would increase the economic burden on our already financially strained health-care system and expose more patients to harmful radiation.
Recognizing this, the research team used their findings to build a prediction model to determine the likelihood of having CAC before the age of 56 based on traditional risk factors such as age, race, gender, education, smoking history, cholesterol, body mass index and blood pressure.
Using the model, the researchers were able to group patients into low or high risk. Applying their model to the data from CARDIA, and proposing that CTs be used only for those with a risk at or above the median value, they found that they would be able to reduce the number of individuals screened by 50%, while still capturing 77% of all participants with CAC scores higher than 1 and 95.5% of participants who had had a coronary event.2
Should we start using their prediction model to determine who should get a screening CT? Not yet. More research is needed to determine the downstream effects of applying such a prediction model to the general population. We also need to determine whether widespread testing would curb outcomes without increasing other risks, such as the risk for cancer from the additional radiation exposure.
In the meantime, an alternative strategy suggested by the authors would be to standardize CAC reporting on conventional chest CTs ordered for other reasons. This approach may have some merit.
One study, published in December 2000 by Dr Mettler at the University of New Mexico, found that 19% of all patients seen in his department had had at least one CT scan, and 36% of all patients had had a prior CT scan. Further, he found that the highest percentage of scans was done in patients age 36 to 50.3 While only 9% of those CTs were chest CT scans, the finding supports that it may be reasonable to obtain CAC scores from existing data for precisely the age group that we are interested in risk-stratifying.
This approach, coupled with a more traditional evaluation of modifiable risk factors, could help identify younger individuals who are at risk for adverse atherosclerotic events and prompt earlier prevention. It may trigger earlier lifestyle modifications and possibly even drug therapy — all without exposing individuals to additional radiation exposure.
- Friedman, GD, et al. “CARDIA: Study Design, Recruitment, and Some Characteristics of the Examined Subjects.” Journal of Clinical Epidemiology. 1988. 41(11):1105-1116.
- Carr JJ, et al. “Association of Coronary Artery Calcium in Adults Aged 32 to 46 Years With Incident Coronary Heart Disease and Death.” JAMA Cardiol. 2017. doi: 10.1001/jamacardio.2016.5493. [Epub ahead of print]
- Mettler FA, et al. “CT Scanning: Patterns of Use and Dose.” Journal of Radiological Protection. 2000. 20(4):353-359.