CardioExchange Archive

Imaging tests for cardiovascular risk assessment hold great promise.  Both coronary artery calcium (CAC) scanning and carotid intima-media thickness (CIMT) testing have been shown in multiple prospective studies to predict cardiovascular outcomes and, more recently, to improve risk reclassification based upon the Framingham Risk Score.  Coupled with frustrations about the performance of the Framingham Risk Score as well as the movement towards personalized medicine, it is understandable why there is great enthusiasm for broader implementation of these tests.  This enthusiasm has taken tangible form in the Texas Atherosclerosis Imaging Bill, HB 1290, which was passed by the Texas Legislature in 2009 mandating insurance coverage for CAC scanning or CIMT testing every 5 years in an accredited laboratory for men aged between 45 and 75 years and women aged between 55 and 75 years who also have diabetes or “a risk of developing coronary heart disease, based on a score derived using the Framingham Heart Study coronary prediction algorithm, that is intermediate or higher.”

The question is: in our intention to do something, are we sure we know what it is we are doing?  And more importantly, is our understanding of these tests and their full implications for population level implementation at a stage where legislative action is warranted? In a recent editorial, I tried to address these issues by taking a closer look at Texas HB 1290.

While some have argued that legislative coverage mandates are never warranted, there are some prerequisite questions that should reasonably be asked before considering such tools: How many people will this affect?  What are the costs?  What are the risks?  How many lives can we save or CVD events can we prevent?  Is there agreement on how to use these tests and interpret the results?  What do the experts say about how we should use these tests? What do patients think? Insurers? Public health officials?

To the extent that these data are available in public testimony and records, it seems that most of these questions were either not addressed or not in sufficient detail commensurate with such a novel bill with broad implications.  In my calculations, if all people in the designated age range and risk category specified by the bill were scanned, this group would comprise 2.4 million individuals with an initial cost of $480 million.  Those are astounding figures that alone should give us pause to ask “what are we getting in return?” To be sure, there would almost certainly be a large number of patients at high risk for CVD events who would be detected (~285,000 by my calculations), and intensifying preventive therapies in this group may globally improve cardiovascular outcomes.

However, this later point has several caveats.  First of all, the majority of patients in age and risk category would already have an indication for statin therapy, and it is unclear what additional benefit is gained from intensification of statins in primary prevention.  In addition, as we move closer to “treat all” (as we are likely to see additional groups recommended for lipid lowering therapy in the upcoming ATP IV), the utility of these tests from a population level are diminished. Finally, the reduction in CV events would have to be balanced against the radiation risks and incidental findings in this asymptomatic population.  It is possible (or even probable) that these atherosclerosis imaging tests would still end up favorable, but these calculations were certainly warranted before seeking a legislative mandate.

Many detractors of atherosclerosis imaging tests have focused on the lack of randomized clinical trials evaluating the impact of these tests on improving clinical outcomes.  While a critical point, there are several other more proximal issues that need to be clarified before pondering a legislative mandate.  For example, the “intermediate risk” group is a very logical target based upon a Bayesian approach, but this group can be defined in many different ways.  Just shifting this group from 10-20% 10-year risk to 6-20% 10-year risk would add several hundred thousand additional Texans for screening eligibility.  In addition, focusing on the 10-20% risk group would shortchange the potential utility of these scans in women as there are few “intermediate risk” women in the population, and more than four times as many men compared with women are eligible for atherosclerosis imaging under HB 1290.  In addition, there is still no universal consensus on the appropriate interpretation of and response to specific test results.  In my personal practice, I have assumed the care of patients that were previously treated as if they have a “disease” when they have small amounts of coronary calcium at a younger age, and others who were told they were just fine with the same findings.

I have two disclosures for this blog: 1) I am a Texan 2) I order coronary artery calcium scans.  For the former, I felt the need to look closely at this legislation to evaluate its global ramifications for people in this state.  For the latter, I have detailed discussions with each patient about the risks and benefits and how we may change our management based upon the results before we order these tests. But the leaps of evidence and understanding required for individual patient-doctor decisions, to population screening, to legislative mandates are vast and we must tread carefully before we invoke legislative action.