February 28th, 2011

What is the Role of CV Screening Tests in Medicine and Legislation?

Three papers in Archives of Internal Medicine scrutinize the role of cardiovascular screening tests not only in medicine but in legislation. In the first article, Nicholas Wald and Joan Morris introduce a new interactive tool that determines the detection and false-positive rates of screening tests. The authors illustrate the value of the tool with the examples of CRP, coronary calcification, glycated hemoglobin, and the QRISK score.

In an accompanying editorial, Thomas Wang writes that the tool “illustrates just how poorly most risk markers perform as screening tests.” He notes the inherent limitation of most screening tests, since “use of these tests requires that the screening threshold be set so low that most who screen positive for events will never have one, or so high that most cases of disease will be missed.”

In a separate commentary, Amit Khera discusses the “broad implications” of a 2009 Texas law mandating insurance coverage for imaging tests used for CV screening. Khera writes that the bill was passed based on input from the controversial Society for Heart Attack Prevention and Education (SHAPE), with no input or support from the AHA or ACC, and with no basis in evidence derived from randomized and controlled clinical trials. “The added costs and potential risks of these imaging tests necessitate a higher level of evidence before considering a broad legislative mandate,” Khera writes.

In an editor’s note, Rita Redberg writes that “at a time when states are facing crises in health insurance spending and cutting lifesaving treatments, and when Texas leads the nation in the percentage of residents without health insurance, it is remarkable that Texas has chosen this path.”


One Response to “What is the Role of CV Screening Tests in Medicine and Legislation?”

  1. Clinicians out to prove their point see what they are looking for; objective physicians see what they are looking at. During a time when more Americans die from coronary disease than all cancers combined and while traditional risk factors fail miserably at identifying risk; it is remarkable that Redberg continues to wage war against atherosclerosis imaging, technology that could make a real difference.

    Apparently the Texas Legislature is unhappy with the tragic statistics of coronary disease in this country even if some of the “medical thought leaders” resist change. SHAPE is controversial only if you think that we should not be doing better than our current pathetic track record of predicting and treating coronary vascular risk. 25% of Americans over age 45 are taking statins. 14% of subjects presenting with their first MI were taking statins. Considering that statin reduces events by <40%, it is clear that there is almost no distinction of statin usage based on real risk.

    SHAP is not the ACC or AHA however it is composed of highly credible cardiologists and researchers who have done exhaustive research on heart attack and stroke prevention and deserve more respect that Khera gives them. To criticize SHAPE due to “no basis in evidence derived from randomized and controlled clinical trials” is a foolish criticism as our use of Framingham risk stratification is also without basis in evidence derived from randomized controlled trials.

    Wang is correct that risk markers are poor; this is fact, not opinion. Coronary calcium imaging is not a risk marker; it is a measure of disease with amazing accuracy. There are essentially no false positive coronary calcium scores. The only thing more predictive of heart attack risk than the initial calcium score is the rate of change in the calcium score over time.

    Coronary calcium is superb as a screening test as illustrated in MESA with normal LDL subjects who were determined to be at risk by HS-CRP (Jupiter equivalents). Coronary calcium determined the 50% with calcium scores of 0 and almost no risk who could only be injured by statin therapy. Coronary calcium also identified the top 25% with calcium scores above 100 and therefore the highest risk who needed secondary prevention. Those “Jupiter like” subjects with a calcium score between 1 and 100 could be treated with diet, exercise and statin reserved for those in the top quartile by age and gender. A follow up calcium score could determine who needs more aggressive therapy.

    It is penny wise and pound foolish to be concerned about the cost of atherosclerosis imaging considering that in America, the combined medical and non-medical economic consequences of coronary disease is over 400 billion dollars annually. I submit that with appropriate application of atherosclerosis imaging, we could reduce this cost by 90% for an investment of less than 4 billion dollars annually.

    Competing interests pertaining specifically to this post, comment, or both:
    Using EBT coronary calcium imaging and carotid ultrasound, I have been able to dramatically reduce heart attacks and coronary death in my internal medicine practice including 500 subjects over age 65, many with co-morbidities. 0 heart attacks and 0 strokes in 2010.