The American Journal of Managed Care August 2014
Does CAC Testing Alter Downstream Treatment Patterns for Cardiovascular Disease?
To assess if coronary artery calcium (CAC) scans influence treatment patterns as reflected by subsequent rates of cardiac imaging and therapeutic interventions, and their effect on ischemic events downstream.
Longitudinal observational study from January 1, 2005, through August 31, 2011, using a large managed-care medical and pharmacy claims database.
Two cohorts were evaluated: CAC patients who received CAC testing, and Reference patients, subject to preauthorization, who were denied CAC scans. Patients were adults less than 65 years old. Index date was CAC scan date for CAC and pre-authorization request date for Reference. Patients were stratified into high-risk and non–high-risk categories; outcomes were analyzed only for non–high-risk where CAC scores could potentially modify risk classification. Cardiac imaging, coronary revascularizations, and pharmaceutical interventions were evaluated for 6 months post index and adverse ischemic events were assessed using all available follow-up time.
The study included 2679 CAC and 1135 Reference patients. Among non–high-risk patients, similar proportions of both groups received an imaging test within 6 months (23.2% vs 23.8%, respectively; P = .5); revascularization rates and pharmaceutical utilization were similar. Adverse events were rare. Age-sex adjusted incidence rate ratio for adverse events was 1.1 (95% CI, 0.36-3.38) among CAC relative to Reference. High-risk patients, considered inappropriate for CAC testing, represented 20.2% and 23.5% of CAC and Reference, respectively (P <.05).
Patients having CAC scans were not associated with fewer downstream ischemic events nor with reduced subsequent imaging and therapeutic interventions among non–high-risk patients. Results also indicated inappropriate testing of high-risk patients.
Am J Manag Care. 2014;20(8):e330-e339
This is the first study to compare downstream differences post scan in the rates of additional diagnostic testing, therapeutic interventions, and ischemic events between patients who received coronary artery calcium (CAC) scans, and controls, who were denied CAC scans because their health plans did not cover the procedure, within a large, real-world, managed-care population.
The findings in this study, consistent with those of prior, largely clinical studies, indicated that there were no significant differences in treatment patterns or ischemic events during the post scan, follow-up period.
- While questions about the value of CAC scans persist, they are still being ordered for asymptomatic patients, raising policy questions that may be resolved by additional studies in larger patient populations and for longer durations.
An estimated 33% of the adults in the United States are affected by coronary artery disease (CAD),1,2 and along with such high prevalence have come substantial and increasing rates of morbidity.1 While relative mortality rates attributable to cardiovascular disease (CVD) declined 33% in the United States from 1999 to 2009, disease burden remained high. CVD was associated with 1 of every 3 United States deaths in 2009, 32% of the 2.4 million overall. Of 2009 deaths, coronary heart disease alone caused approximately 1 in every 6, and stroke 1 in every 19. The total direct and indirect cost of CVD and stroke was estimated at $312.6 billion in 2009.3 These sizable and growing burdens have driven efforts to evaluate and better understand cardiac risks in asymptomatic patient populations.4-11
Coronary artery calcium (CAC) scanning, a screening tool that detects subclinical coronary disease in asymptomatic populations, is noninvasive; it can be performed in a few minutes while the patient is fully dressed.4-9,12-14 A number of older studies suggest that CAC scores are directly correlated with coronary atherosclerosis, and may represent a marker for plaque burden.15-19 CAC identifies with calcified plaque,20 and CAC score is considered a predictor of coronary death and nonfatal myocardial infarction (MI).21 Furthermore, some studies have reported high sensitivity (true positive for the presence of coronary artery disease), greater accuracy and reproducibility when CAC is measured with coronary computed tomography (CT).15,18,19 CAC utilizes radiation, and accumulating evidence about radiation exposure and cancer risk remains a concern, especially in women and middle- aged and younger persons.20,22-24 However, results from recent studies suggest that advanced scanning tools may reduce effective radiation doses.25,26
The primary policy concern regarding CAC scanning is whether it provides—on its own, and/or when added to existing tests—a better assessment of future risk of cardiac events than do scoring methods such as the Framingham Risk Score (FRS)14,27 and the National Cholesterol Education Panel (NCEP) Adult Treatment Panel (ATP) III guidelines,28 and whether it leads to improved outcomes for patients.
Anand et al reported, after following 510 asymptomatic patients for an average of slightly more than 2 years, that CAC scores were a better predictor of ischemic events and related short-term cardiovascular outcomes than established measures of cardiovascular risk factors such as the FRS.29 Similarly, based on data from the multi-center prospective longitudinal trial, Multi-Ethnic Study of Atherosclerosis (MESA), Detrano et al concluded that CAC scores yielded better predictive information relative to the FRS.12 Using data from the MESA trial, Polonsky et al added CAC scores to FRS risk factors to examine the prediction of incident CHD (including soft events such as revascularizations). The authors concluded that the addition of CAC scores produced significant net reclassification improvement, an indicator of the amount of adjustments between risk categories.30 Similar reclassification rates were observed in a study by Erbel et al that added CAC scores to both the FRS and the NCEP ATP III scores when predicting hard events (ie, nonfatal myocardial infarction and coronary death).31
CAC testing, however, may not be useful for everyone. For high-risk patients, CAC scoring does not produce any improvement in event prediction, management, or outcomes. 5 The 2010 American College of Cardiology Foundation/ American Heart Association (ACCF/AHA) Task Force on Practice Guidelines indicated that CAC measurements were reasonable for the assessment of cardiovascular risk among asymptomatic adults at intermediate risk, defined as 10%to 20% risk of a cardiac event within 10 years.6,12,14 The guidelines also indicated that the measurement of CAC may be appropriate for patients at low to intermediate risk, defined at 6% to 10% risk of a cardiac event within 10 years.6,14,32 The guidelines indicated, however, that CAC was not appropriate for individuals at low (6% or lower) risk of experiencing a cardiac event within 10 years.4,6,12,14