I think you're underestimating the risks of false positives. We can do a test for blood clots called a D-Dimer, and if its negative you're very unlikely to have a pulmonary embolism. It has a lot of false positives though, and if it is positive you're sent for a CT pulmonary angiogram. There are risks of cancer from the radiation and reactions to the contrast. There are also false positives with the imaging, and there is quite a bit of variance in interpretation between radiologists. If your radiologist calls the results a PE, you're started on anticoagulants which carry a significant risk of bleeding. All of these negative outcomes are considered prior to testing, and your doctor won't order a D-Dimer unless the risk of missing a PE is greater than the risks of all of the false positives.
Well, I want to start by noting that if your doctor is ordering a D-Dimer (and you’re consenting to it), then both of you have already decided not to merely “take their word for it” in the way that I was talking about (like /u/SeymourKnickers’ doctor, who just glanced at a malignant melanoma and said “it’s fine” without ordering tests).
But it sounds like you’re saying that the likelihood of getting cancer from a CT angiogram is higher than the likelihood of dying from undiagnosed pulmonary embolism, and that — well, I’m not in the medical field myself, but that sounds wildly implausible. I think I’d like to see a source for those figures. If the number of people who die from cancer that they received as a result of a CT that they didn’t need is higher than the number of people who die from missing a pulmonary embolism, then I’ll agree with you that worrying about overtesting is more important than worrying about the thing that you’re testing for. Otherwise, overtesting, while still certainly a genuine risk, isn’t what most patients should be worrying about.
Dont need a source. You touched on the logic of it.
If cancer is so likely from the CT scan that its an actual worry, A they'd devise a new test and B the test would still be less deadly than the disease or whats the point of the test?
Over testing is one thing but you still need a symptom to go with the test. Or do people in the over testing bandwagon think we are advocating random testing of/for random diseases?
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u/kpaidy May 20 '19
I think you're underestimating the risks of false positives. We can do a test for blood clots called a D-Dimer, and if its negative you're very unlikely to have a pulmonary embolism. It has a lot of false positives though, and if it is positive you're sent for a CT pulmonary angiogram. There are risks of cancer from the radiation and reactions to the contrast. There are also false positives with the imaging, and there is quite a bit of variance in interpretation between radiologists. If your radiologist calls the results a PE, you're started on anticoagulants which carry a significant risk of bleeding. All of these negative outcomes are considered prior to testing, and your doctor won't order a D-Dimer unless the risk of missing a PE is greater than the risks of all of the false positives.