The argument is that some blood tests aren't that effective and you get false positives. For certain tests that might be true. However, aren't we still better off if we can perform all tests more cheaply and on a more regular basis? Having a few tests that aren't effective does not invalidate the entire goal.
>The effectiveness of screening for a given disease before signs and symptoms appear depends on a host of conditions... including whether there’s an effective treatment for whatever is found...
There are so very few ways to even think about, treat, or even test for the earliest stages of a disease precisely because we don't have data about the early stages. Getting that data would certainly provide for data upon which to design better early-stage therapies. The use of measuring PSA (as mentioned) works great in more advanced stages of prostate cancer, and probably doesn't work well for early stages - but if we had good and regular testing we could find an indicator for those early stages.
So which comes first, the readout, or the therapy? Of course, it's the readout. Just because we don't have those new early-stage-targeting therapies yet doesn't mean a new array of (accurate and reliable) testing wouldn't be extraordinarily helpful.
Blood tests are a single evidence point in a chain of thinking.
You do a blood test to confirm your initial theory, not as an exploratory exercise. You need it to be accurate, because otherwise you'll have to do it multiple times. (which unless the number of tests required is cheaper than the original, its pointless)
I agree with your comment. Beyond the false premise, I think that this fivethirtyeight piece is extremely dangerous because it seems to prefer shocking headlines over actually depth. i.e. "We Don’t Need More Blood Tests" and the infographic "How accurate tests can be mostly wrong."
What false premise? Fivethirtyeight is not wrong. In this case, with seemingly reliable tests (>90% accuracy), only 27% of positive tests are correct. If you're talking about something that has an invasive next step, like a biopsy, and you decide to increase the number of tests done each year, then you are going to also be increasing the number of unnecessary invasive procedures each year as well.
Take mammograms. It's a fairly non-invasive test for breast cancer. Everyone wants to reduce breast cancer, right? Unfortunately, the data is very much like fivethirtyeight's example. In a 10 year period, 1 in 2 women are harmed by a false positive and 1 in 5 were harmed by an unnecessary surgical procedure. What about the lives saved? None.[0] Screening mammograms only end up harming patients.
While it may make sense intuitively that more screening must be better, the data generally fails to back it up.
If an exploratory test is done for a condition sufficiently rare that a positive is quite likely to be a false positive, then a positive result should not, in the absence of other evidence, lead to an invasive procedure. What action should be taken depends on the particulars of the condition, but just monitoring for actual symptoms of the condition or maybe trying a different test would almost certainly be more sensible options.
The article seems to be decrying additional testing, which is basically just additional information gathering, on the basis that some people might make dumb decisions based on the information. That's probably true, but I don't think it means that more information is a bad thing.
The case of mammography is often brought up for this argument, but is a cherry picked example. Furthermore, it isn't a blood test, so it isn't even what is being argued against by fivethirtyeight.
There is no harm done by extremely accurate testing for HIV. and less accurate tests should be used in screening by medical professionals that know how to proceed from a positive result. Again, blanket statements like "We Don’t Need More Blood Tests" are dangerous
given how 538 seemed to want to be positioned in the market place, I'm pretty disappointed with how similar their model of 'shocking headlines over actual depth' is to what are generally dismissed as low brow competitors
What do you consider cheap? I can get a basic metabolic panel of 26 tests (lipids, glucose, CBC, electrolytes, organ functions) for around $50 as an individual. This includes drawing the blood, shipping and third part profit margins. Imagine the actual costs which are probably around $15 or so. I'm guessing a lot of these basic tests have been automated so they can be done cheaply. So I don't think costs are the main issue with the current technology. There are tests which are much more expensive but those may have manual labor involved and I don't think Theranos can make them any more cost effective.
That's exactly what I was thinking. Sure, if we look at a population then maybe we don't see a remarkable result. But surely we've helped SOMEONE here.
From the article: "which means that only 27% of positive test results are right"
Yes, 27% is not great, but that's still more than 1/4 of the people that had a good result and will live longer or better or whatever. 1/4 of the people got some kind of benefit. Sure, we'd rather see 75% but 27% is SOMETHING and that's worth, well, something I guess. Does the cost mean it's worth it?
For those in the 27% they are sure as heck going to say yes, right?
In the specific case of prostate testing, all they can do is repeat the test. And it likely comes back with the same results.
Many men in their 40s and 50s have high test results. Those same men can live 30, 40 more years with the condition. Or they can die of prostate cancer in 3 years. Or they could get treatment, and lose all use of their prostate for the rest of their life.
It seems like prostate cancer testing is the poster child for "the test tells you something, but often you statistically don't want to act on the test...".
what do you say to the 73% whose lives got negatively impacted? Prostate screening is a great example. Elevated PSAs are indicative of cancer, which people want to get rid of. So they have a procedure done, which often leaves them incontinent. But the reality is that, the majority of the time, prostate cancer remains effectively dormant. The end result is a lot of old men who would have been healthy but are now walking around in diapers because they got a test.
You've missed the other side of the equation, which is: what if there is no cure for the 27% with the supposed condition? What help has been provided then?
What if there are some recommended follow-up treatments, but they are all expensive and risky, with the possibility of terrible complications?
This is how over-diagnosis actually leads to worse outcomes on a population scale. Medicine is often viewed as this big near-perfect algorithm where information is always enabling. In fact, too much information can be counterproductive for a patient and doctor.
