Hi MJ,
"Calcium scam machines" was my smart-mouth way of referring to the electron beam CT machines made by IMAT (now GE). Of course, now there are several kinds of CT machines, and probably they are superior technologically to the old electron beam CT units.
I got involved in the research end of calcium scanning before IMAT even had a product on the market. My involvement there is now minimal, but I more or less try to keep up with things. I have seen lots, I could write a book (but nobody would believe it!). You are right, mainstream medicine continues to be very skeptical, and with very good reason: despite the marketing hype, there is little or no evidence that in the vast majority of cases, calcium scanning does anything more than enrich those selling scans. Worse, there is evidence they can do harm in various ways.
The notion that if only you can detect disease early, that will lead to better outcomes is intuitively attractive, and appeals to those who operate on hope (i.e., most in the medical profession, and most of their patients). The problem is, this often not only doesn't work as planned, but sometimes leads to quite the opposite result. I won't go into exactly why, but suffice it to say that diagnostic testing itself exposes the patient to risk, and can of itself lead to harm. This phenomenon is widely underappreciated, but very fascinating when you delve into the exact reasons why. When you understand something about this, it makes sense, but it is astonishing because it is so paradoxical and ironic, even counter-intuitive.
Here's an example. Some years back, there was a clinical screening study in Poland, in a region where lung cancer rates were very high. They wanted to try to detect lung cancer earlier, and so lead to more effective treatment, which would be expected to decrease mortality rates. I might have some of the details wrong here, but as I recall, they took a group of people and did chest x-rays every 6 months. Another group of people they just let go their merry way and get chest x-rays or whatever as if they weren't part of the study. So these latter were the control group.
They did detect lung cancer at higher rates, and earlier, in the group that got chest x-rays every 6 months. But much to everyone's surprise, they discovered after carefully following all the participants that the group who did NOT get chest x-rays every six months got about the same amount of lung cancer, but did much better in terms of survival.
So, early detection did not lead to better survival, in fact it had exactly the opposite effect.
This sort of thing occurs much more commonly than one might imagine. And, it continues to be underappreciated. But the moral of the story is that you can not assume that early detection of itself is a good thing. You must look at how patients fare in the long-term. And that is only the beginning. There are numerous things that must be analyzed before you can confidently conclude you are helping people.
And, with calcium scanning, such analyses have simply not been done, nor is there even any motivation to do so for the most part, because there is nothing to gain, and lots to lose. There is zero evidence that calcium scanning in any group of patients whatsoever improves long-term outcomes. If you are selling calcium scans, and telling people you can detect this or that at a very early stage, do you really want to spend millions of dollars on a clinical trial to find out if your patients are doing better or worse as a result of calcium scanning? What happens to you if it turns out they are not benefitting? Or worse, if they are being harmed? And since this has been the case many times in the past under similar circumstances with many other diagnostic/prognostic screening tests, there is a very real chance this will be the case with calcium scanning. Do you really want to go down that road? Why not just let sleeping dogs lie?
I think eventually we may find that in small, very selected patient groups, calcium scanning might have a beneficial effect. But this is only a guess, and to the best of my knowledge even this notion has no support from evidence. I think it is virtually a foregone conclusion that calcium scanning applied to the population at large will have a net detrimental effect on a significant proportion of the population. A minute fraction will be helped, but this number will be totally overwhelmed by the vast majority who either derive no benefit at all, or who are harmed by the test.
T |
