Should you get a calcium score or cardiac CTA?
Everyone in the medical field knows that it’s pretty common to get medical questions from friends and family.
Often these questions are hyper-specific and impossible to answer without a lot more information about the clinical context.
These questions are also frequently about skin issues, and most of you would probably be appalled to learn how little most doctors know about rashes.
I had a question from a friend the other day, asking if his mom should get a stress test or a CT angiogram, because a friend of theirs recently went for a stress test that she “passed” but then ultimately need to have three stents after a CT angiogram showed her severe blockages.
Obviously, this is an impossible question to answer specifically without a lot more information. If a doctor gives a blanket recommendation that every person get a specific test regardless of their individual characteristics, that’s at best an oversimplification and at worst just plain wrong.
But there are some general principles that we can use to frame how we think about diagnostic testing.
What information are you trying to get with testing?
The most common reason that we do a medical test on someone is to figure out why they are having some type of symptom.
After all, the goal of medical care should be to either make you live longer or feel better.
If you don’t feel unwell in the first place - read: you have zero symptoms - then the bar for testing or treating becomes quite a bit higher.
Using a bar like that for testing eliminates a huge amount of what is done in the medical system, and you can certainly make the case that doctors often over test and overtreat (I know that I have made that case before).
Most medical tests for asymptomatic people aren’t going to easily clear the hurdle of something that obviously makes you live longer.
It is really hard to show that something saves lives of healthy people because you need to study them for so long that a high quality clinical trial often becomes too expensive or impractical to conduct.
To give an example: a coronary artery calcium (CAC) score is a hugely common test to detect asymptomatic heart disease via CT scan.
But there’s never been a clinical trial to show that obtaining a calcium score prevents heart attacks or cardiac death.
We know that higher calcium scores are linked to elevated risk, but there isn’t actually any proof that acting on a calcium score lowers risk of heart disease.
There is another reason that I can think of to get testing done: if it influences long term medical treatment or lifestyle choices
If there isn’t evidence that calcium scores reduce heart disease risk, then why do I order them for patients?
Let me make the case:
If you think about the timeline of heart disease, you recognize this disease takes decades to happen rather than months or years.
A high calcium score helps to better personalize a risk assessment by providing additional information about a patient’s anatomy and risk of heart attacks
Seeing coronary calcium on a CT scan (literally hardening of the arteries) influences treatment decisions and lifestyle choices.
If you look at a more comprehensive screening program for cardiovascular disease, my read of the evidence is that it supports cardiovascular screening.
Plus, the evidence is compelling that lifelong low blood pressure and cholesterol numbers means much lower heart disease risk:
But truthfully, often the more compelling reason to get testing done is because people want to understand their own disease risk.
In this case, testing can be motivating when it comes to lifestyle.
What impact does diagnostic testing have ?
The test is only as useful as what you do with it.
No diagnostic test changes outcome in the absence of a change in treatment or a lifestyle change.
I’ve had patients who have been motivated to exercise more, eat better, or take their medications more regularly after a cardiac risk assessment showed that they have higher risk than might be expected based on looking at traditional risk factors like blood pressure and cholesterol.
But there’s a flipside to the “knowledge is power” argument.
The first counter argument is the stress argument - knowing that you have the early stages of heart disease can transform regular people into anxious patients.
Suddenly the knowledge of a high calcium score makes every ache or pain worrisome. It can lead to other tests, emergency room visits, and lots of stress.
The second counter argument is the fact that these tests are imperfect and you can have a heart attack even with a calcium score of zero.
Plus, the lifestyle actions that we’re talking about - regular exercise, not smoking, a healthy diet - have lots of benefit regardless of what your calcium score is.
And that brings us to the question about what we do medically with an abnormal screening test.
Be honest with yourself about what the test will change
I had a patient come to me recently who told me that she wanted to do any test that would help to understand her heart disease risk and then she would do everything she could do reduce it.
She had heard about a calcium score on a podcast and thought that she should have one done.
But then when I told her that I would almost certainly recommend medications if her calcium score was over zero, she thought that suggestion was beyond the pale - why would I prescribe her medications if she’s never had a heart attack and doesn’t have symptoms?
This gets to a disconnect between how people often perceive medical decision making versus how doctors perceive it.
Most doctors won’t order a test unless they know how they’re going to respond to a result - I wouldn’t order a calcium score for a patient unless it was either going to change my management or my advice to them.
But sometimes patients are not considering the full spectrum of possibilities when it comes to the decision about what to do next.
If a test result isn’t going to change your treatment, then why would you bother getting the test in the first place?
And the corollary for patients: if an abnormal test result is not going to persuade you to take medications that are recommended, then why would you want to expose yourself to the radiation, stress, and interruption to your schedule that comes with testing?
The first principle is that you must not fool yourself and you are the easiest person to fool
This is a great quote from Richard Feynman that I often find myself thinking about when discussing preventive care with patients.
We are all guilty of telling stories to ourselves about what we’re going to do to be better people - we’ll eat better, we’ll prioritize our sleep, we’ll exercise more, we’ll start a meditation program.
And some of us take action, but many of us don’t.
While untreated risk factors for chronic disease like high blood pressure, high cholesterol, and metabolic syndrome certainly can be fixed with lifestyle changes, the data suggests that most people aren’t going to implement these things in a sustainable way.
Quite often I have a patient tell me that they’re about to start exercising and eating better and so we shouldn’t start a blood pressure medication or a statin and give them a chance to do things without phamaceuticals.
This aversion to medications - either because of concern about side effects or because of a variation of the naturalistic fallacy - is understandable and reasonable.
But too many people fool themselves into thinking that they’ll be able to get their risk factors under control without medications and end up with years or decades of untreated medical issues that increase the risk of heart attack and stroke.
And so I’ll conclude this with a recommendation that I give to my patients all the time (which is exactly what I told my friend about his mom’s testing): you should only get a test done that you’re willing to act on, and if the test is going to make no difference the ultimate clinical decision making, then there isn’t much point in doing the test in the first place.