This story reports that testing generally healthy people for the presence of calcium deposits on the walls of their coronary arteries may provide clues about who is more likely to die over the following 15 years. That’s an interesting finding that was well worth writing about. However, the story then runs beyond the evidence to feed speculation that coronary artery calcification (CAC) scans could help improve treatments, something this study did not look at. We also have some concerns about the story’s description of the physiological aspects of heart disease.
Tests are really only useful when the results make a difference, such as by matching people with appropriate treatments. While this study indicated that, in one group of patients, those with high coronary artery calcification scores were more likely to die over the following 15 years, it did not (and was not capable of) showing that such testing could make any difference in their treatment. News reports should make clear the vital distinction between a test result that can lead to useful action (such as fecal occult blood testing that can help identify treatable colon cancer) and a number like age, that merely predicts the risk of death without offering anything people can do about it.
The story helpfully notes that the CAC test costs about $100, which matches price quotes from other sources, though the price may be higher in some parts of the country. The story would have been even more useful had it noted that the cost of the test may not be covered by insurance.
The story reports that CAC testing can provide health benefits, but that’s not what the study looked at.
The story includes a claim by an expert that this study confirms the usefulness of CAC testing for determining the best treatment of people who do not have symptoms of heart disease, but do have high cholesterol or a family history of heart problems. However, the research article cautions that, “Despite evidence of increased risk, current effectiveness evidence does not support targeted treatment of patients with high-risk CAC scores to improve outcomes.” In other words, even if people in this study who had higher scores were more likely to die, this study does not provide any evidence that more or different treatment would extend their lives.
The story also quotes a researcher saying that telling someone they have a high CAC score “can be a very potent motivator” for changing lifestyle or sticking with treatment. However, once again, the actual text of the research article undercuts this claim, noting that any effect of CAC test results on patient behaviors “cannot be quantified”. What’s more, health behavior literature generally indicates that test results by themselves tend to have little effect on people’s behavior, unless ongoing support is provided.
Lastly, the story describes a 68% increase in risk of death for those with small amounts of CAC and a risk that was “6 times greater” for those with another group. But these are relative comparisons that are difficult to interpret. It would have been easier and more informative to simply give the absolute rate of death in each group as the study did — these rates were 3% in the zero CAC group, 6% for those with small amounts of CAC, and 28% for those with large amounts of CAC.
The story does not discuss any potential harms of CAC testing. It fails to tell readers that the researchers noted in their article that for every 10,000 people screened, about 12 would develop cancer. That means that subjecting 100 million adults to this test would be expected to result in 120,000 additional cancers.
Even if that cancer burden were deemed acceptable, patients sent for additional testing (such as catheter imaging) or prescribed drugs or procedures would be exposed to the risks and costs of those tests and treatments.
The story portrays the study as more ambitious and powerful than it actually was. The study compared results from a single test to death records. There was nothing in the study that would support conclusions about how to improve treatment or whether the results could be used to improve health outcomes, yet the story tells readers that the study points the way to such benefits. The story needed a nod to the fact that more research is needed to show that CAC scores can be used clinically to provide these health benefits. As the researchers pointed out, “Because
we are presenting observational data, causality with regard to influencing outcome cannot be inferred.”
There was also no discussion of other study limitations. For example, because all the patients in this study came from a single center connected to a military healthcare system, the results may not apply to the general population.
The story blurs the line between a risk factor and a disease. This study merely documented that people with very high CAC test scores have a higher risk of death over the next 15 years. It does not prove either that coronary artery calcium deposits caused those early deaths or that testing and treatment could extend lives, yet the story portrays high CAC scores as a health problem that demands action.
Of course, we’ve already mentioned this concern, and we might have given the benefit of the doubt here if the story had better connected the calcium deposits to the study outcomes. Instead, there are several errors in the description of what happens in heart disease that may serve to mislead or confuse readers about the impact of coronary calcium: 1) Coronary arteries carry blood to the heart muscle (they feed the muscle), not away from the heart as the story states; and 2) The problem with coronary plaque buildup isn’t that it causes the heart to “work harder to pump blood through the body” as the story states; it is that narrowing in the coronary arteries deprives the heart muscle of blood, causing angina (chest pain), and 3) Clots in coronary arteries don’t break off and cause strokes in the brain; the rupturing of plaque leads to blockage in the coronary arteries, again depriving the heart muscle of blood (causing a “heart attack” or myocardial infarction).
The story goes a long way toward satisfying this criterion by including comments from an expert who was not connected to the research. But it fails to tell readers that some of the researchers receive funding from General Electric Healthcare, which sells scanners used for CAC tests, or from pharmaceutical companies who stand to garner more patients if CAC testing is expanded.
The story mentions the importance of eating right, exercising, and taking medication to treat heart risk factors for improving heart health — which is important to reiterate. However, treatment of heart disease was not the primary point of the study. One of the main reasons for doing this study was to compare the predictive power of CAC tests to some other risk factor assessments, and the story does not mention those other methods.
It is clear from the story that CAC testing is widely available.
The story specifically notes that CAC testing is not new, and that previous research hasn’t assessed long-term health risks associated with CAC.
The story includes an independent expert and has quotes not included in the Emory University news release about this study.