Reference: JAMA. 2023 May 23;329(20):1768-1777
Practice Point: Coronary calcium scores may be slightly better than pooled cohort equations for appropriately classifying risk of coronary heart disease, but that doesn’t mean everyone should get a coronary CT.
EBM Pearl: Area under the curve (AUC) is often used to display data for prediction tools. The graphical representation of the information can be worth a thousand words.
The only thing worse than pooled cohort equations (PCE) such as the Framingham Risk Score or ASCVD calculator is a coronary calcium score (CCS). There, I said it. The thought behind coronary calcium scoring is that coronary artery calcium is a marker of subclinical atherosclerosis in healthy-appearing adults which can predict future clinical coronary heart disease (CHD), allowing the opportunity to intervene and potentially prevent major coronary events. However, the clinical utility of CCSs for patients with any score higher than zero has been consistently questioned in clinical studies. This hasn’t stopped patients from wanting them or providers from ordering them, even if they aren’t covered by insurance and the order in the EHR literally states “CT heart cash-and-carry” like it does at my institution. However, a study just published in JAMA makes a case for adding CCSs to PCEs to improve precision when estimating CHD risk. Coronary CTs for everyone, then?
The authors took prospective cohort data from the MESA (n = 1991) and Rotterdam Studies (n = 1217) of White European adults (median age 65) without clinical CHD who were not on a statin and estimated participants’ baseline 10-year CHD risk based on several PCEs, with and without a CCS. The median predicted 10-year CHD risk was 6-7%. Participants were followed for about 15 years for development of clinical CHD, which occurred in 8-9%. The primary outcome essentially measured whether adding the CCS to PCEs did a better job at classifying CHD risk. According to this study, it did. But we already knew that PCEs overestimate risk of CHD, so it’s not all that surprising that CCS would improve the accuracy. Again I ask, coronary CTs for everyone, then?
Please, no.
First of all, let’s be clear that a CCS is not recommended for anyone with established CHD. Second, a coronary CT isn’t for people with acute anginal symptoms as it’s not great at detecting coronary artery stenosis. Best case scenario, it’s for people at low- to intermediate- CHD risk who for whatever reason are on the fence about a statin or need more motivation (than your advice) to eat healthier and exercise. And for what it’s worth, those statin fence-sitters have a point, given they and 499 of their friends would need to take a statin daily for 5 years to prevent one more of their deaths. (The NNT for statins to prevent one cardiovascular death over 5 years is 500 for a person with a 10-year ASCVD risk of 10%, so it isn’t the magic pill people think it is.)
So if this study is telling us that adding CCS to PCEs slightly improves CHD risk classification, please forgive us if we say “so what?” A cath would help estimate CHD risk too, but that doesn’t mean we should do it. Doing more coronary CTs would be one more example of overuse to do a slightly better job at (over)estimating CHD risk. At the risk of sounding like a broken record, maybe tell your patients to spend the money they would have spent on their cash-and-carry CT on a gym membership instead.
For more information, see the topic Coronary Artery Calcium (CAC) Scoring and Clinical Use in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Katharine DeGeorge, MD, MS, Deputy Editor at DynaMed and Associate Professor of Family Medicine at the University of Virginia. Edited by Alan Ehrlich, MD, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School; Dan Randall, MD, Deputy Editor at DynaMed; Nicole Jensen, MD, Family Physician at WholeHealth Medical; Vincent Lemaitre, PhD, Senior Medical Writer at DynaMed; Elham Razmpoosh, PhD, Postdoctoral fellow at McMaster University; and Sarah Hill, MSc, Associate Editor at DynaMed.