Risk-Benefit of Coronary Calcium Scores May Preclude Inclusion from Traditional Risk Assessments

Kathy Bell, PhD

Although the benefit of coronary artery calcium (CAC) scans has been touted by a multitude of studies in recent years, new data suggests the addition of CAC score (CACS) to traditional cardiovascular disease (CVD) risk assessments provide did not provide clinical value.

A systematic review and meta-analysis of half a dozen cohort studies, results of the study demonstrate CAC scoring provided a modest gain in incremental value when added to traditional cardiovascular risk assessments, but this was often be outweighed by costs, rates of incidental findings, and radiation risks as most patients reclassified as intermediate or high risk by CAC score did not have a cardiovascular event during follow-up.

“Although a CACS may have a role for refining risk assessment in selected patients, which patients would benefit remains unclear. At present, no evidence suggests that adding the CACS to traditional risk scores provides clinical benefit,” wrote investigators.

In 2018, the US Preventive Services Task Force recommendation statement on CACS proclaimed insufficient evidence existed to assess the benefits versus harms of including CACS to traditional risk assessments for CVD in asymptomatic adults. Led by Kathy Bell, PhD, of the School of Public Health at the University of Sydney, the current study was conducted with the intent of assessing whether data published since the end of the USPSTF review for their 2018 recommendation statement might provide further clarity on the value of CAC scans when added to traditional risk assessments

Investigators performed a multiple iteration citation search to identify relevant studies for inclusion. Using the initial systematic review conducted by USPSTF statement authors, investigators performed an initial backward and forward citation search of the systematic review. From their searches, investigates identified 2772 articles for potential inclusion. After exclusion of duplicates and further screening, 6 cohort studies were deemed eligible for inclusion.

Studies were considered eligible if they were cohort studies conducted in primary prevention populations that assessed and reported incremental discrimination with CACS for estimating the risk of a future cardiovascular event against a CVD risk calculator recommended by national guidelines. For the purpose of analysis, cardiovascular risk calculators of interest were the Framingham Risk Score, QRISK, pooled cohort equation, NZ PREDICT, NORRISK, and SCORE.

The 6 studies deemed eligible for inclusion included 17,961 participants with 1043 CVD events. Studies ranged in size from 470 to 5185 participants with a range of mean ages of 50±10 to 75±7.3 years and mean follow-up of 5.1 to 10.0 years. Investigators noted 3 studies were conducted in US patients and the 3 remaining studies representing patients from the Netherlands, Germany, and South Korea. Investigators also pointed out most of the studies included were at low risk of bias, with the exception of 1 study, which was rated as being at high risk of bias due to nonrepresentativeness of the study sample.

Results of the investigators’ analyses suggested the C statistic for CVD risk models without CACS ranged from 0.693 (95% CI, 0.661-0.726) to 0.80 (Not reported) and the pooled gain in C statistic from adding CACS was 0.036 (95% CI, 0.020-0.052) with moderate heterogeneity (I2=56%). According to investigators, the heterogeneity may partially explained by the outcome measures, with the gain in C statistic appearing larger when using coronary heart disease events (gain in C statistic, 0.049 [95%CI, 0.036-0.062]; I2=0)as the outcome rather than CVD events (gain in C statistic, 0.029 [95% CI, 0.011- 0.047]; I2=39%), but tests for interaction demonstrated the apparent difference was not statistically significant (P=.08).

Additionally, when assessing those who were reclassified from low risk to intermediate or high risk by CACS, results indicated the range of those experiencing a CVD event during follow-up was 3.6% to 14.5%, with the range of those not experiencing a cardiovascular event at 85.5% to 96.4%. Among those reclassified from intermediate or high riskto low risk by CACS, the proportion of patients without a CVD event during follow-up ranged from 91.4% to 99.2%.

In a related editorial, Robert Gallo, MD, of the Stanford School of Medicine, and David Brown, MD, provide perspective on the clinical applicability of the data from the study’s investigators and its addition to the current knowledge base surrounding CACS.

“The work by Dr Bell and colleagues adds an important update to the literature on the limited influence of CACS on model discrimination and contributes to existing questions and concerns regarding its role in primary prevention screening,” Gallo and Brown wrote. “Until ongoing outcomes studies indicate a clinical benefit of CACS screening to counterbalance its potential harms, we agree with the US Preventive Services Task Force and believe that adherence to the ancient medical dictum, primum non nocere, should dictate a pause in adding CACS screening to standard clinical risk models for primary prevention of CVD.”

This study, “Evaluation of the Incremental Value of a Coronary Artery Calcium Score Beyond Traditional Cardiovascular Risk Assessment,” was published in JAMA Internal Medicine.