Firstly, I agree. You can't hide from that, and research should be upfront with the limitations of the work.
Other commenters have noted that the sensitivity is 100% with specificity 82% (false positive rate being 18%). I wanted to provide my own take on what that means for me as a future provider (I'm considering becoming a neurologist after medical school). I'm assuming to the data science crowd here, it's almost second nature to know what these numbers really mean in practice, but maybe I can provide some outside perspective.
When considering screening tests in medicine, we have to always balance the benefits and risks of conducting these tests on patients. We have to figure out how reliable a test is, and how patients benefit from earlier detection.
In this case, it's an imaging test, so noninvasive. However, it's a test that requires radiation (positron emission tomography or PET). So we already have to determine if that extra radiation dose is worth the increased risk for something like cancer. In an elderly population, it's almost certainly worth the scan given the radiation would not significantly impact their decades of accrued radiation damage.
Now, what happens if a patient has a positive test, 6 years earlier than they would normally? Let's assume for a moment that it was a true positive test. They could receive treatment earlier, which could improve their quality of life. They could adjust their risk factors to slow down the progression of disease. The treatment could have side effects, such as increased blood pressure. If we apply that to a large population scale, would we increase mortality associated with heart disease by treating patients with suspected Alzheimer's earlier?
Lastly, I wanted to touch on the effects of a screening test with a large amount of false positives. I would argue that a screening test should be allowed to have lots of false positives, simply because we can always do other tests (neuropsychiatric evaluation like MOCA score) to improve our accuracy of detection. However, if we do these other tests, we have to again balance the harms with the risks. Mammograms, for instance, could give false positives that could warrant a breast biopsy. In the case of Alzheimer's, a false positive could lead to stress and depression in an elderly population already at higher risk for stress related disease.
In short, screening tests are great if there's a way to do something about the disease. As far as I know, early prophylactic treatment (with current medications) of Alzheimer's does improve quality of life, slowing progression of the disease manifestations, with relatively few side effects.
You missed some downsides: anguish, more tests for something that isn't a problem, costs, possibly suicides. You may want to read up more on the downsides to breast cancer screenings for reference.
I didn't delve into all the downsides, but I did mention the stress and related depression that could be associated with a false positive. I also noted how there are downsides to mammograms, such as a breast biopsy. We could go a step further and note that some women opt for mastectomies as well, especially for genetic screening (BRCA).
There's plenty to delve into regarding the risks and benefits of screening tests: Here's a good framework for those interested.
Woah is the radiation in an imaging test really so dangerous that you carefully consider whether its worth doing even once? Because uhh i get those pretty often
No, not especially. It's mostly dependent on how early in your life you receive doses of radiation. It's why we tend to stay away from CT scans in pregnant women, or other high dose radiation in kids. However, the obstetrician-gynecologists I worked with drilled into me that if you need a CT scan, do it anyways because technically one CT scan does not exceed the dosage that will cause damage in babies. XKCD made a nice little graphic comparing the dosage of different radiations:
Other commenters have noted that the sensitivity is 100% with specificity 82% (false positive rate being 18%). I wanted to provide my own take on what that means for me as a future provider (I'm considering becoming a neurologist after medical school). I'm assuming to the data science crowd here, it's almost second nature to know what these numbers really mean in practice, but maybe I can provide some outside perspective.
When considering screening tests in medicine, we have to always balance the benefits and risks of conducting these tests on patients. We have to figure out how reliable a test is, and how patients benefit from earlier detection.
In this case, it's an imaging test, so noninvasive. However, it's a test that requires radiation (positron emission tomography or PET). So we already have to determine if that extra radiation dose is worth the increased risk for something like cancer. In an elderly population, it's almost certainly worth the scan given the radiation would not significantly impact their decades of accrued radiation damage.
Now, what happens if a patient has a positive test, 6 years earlier than they would normally? Let's assume for a moment that it was a true positive test. They could receive treatment earlier, which could improve their quality of life. They could adjust their risk factors to slow down the progression of disease. The treatment could have side effects, such as increased blood pressure. If we apply that to a large population scale, would we increase mortality associated with heart disease by treating patients with suspected Alzheimer's earlier?
Lastly, I wanted to touch on the effects of a screening test with a large amount of false positives. I would argue that a screening test should be allowed to have lots of false positives, simply because we can always do other tests (neuropsychiatric evaluation like MOCA score) to improve our accuracy of detection. However, if we do these other tests, we have to again balance the harms with the risks. Mammograms, for instance, could give false positives that could warrant a breast biopsy. In the case of Alzheimer's, a false positive could lead to stress and depression in an elderly population already at higher risk for stress related disease.
In short, screening tests are great if there's a way to do something about the disease. As far as I know, early prophylactic treatment (with current medications) of Alzheimer's does improve quality of life, slowing progression of the disease manifestations, with relatively few side effects.