A study from 2014 could not replicate this:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4167392/pdf/nih...

> Methods: Participants with probable AD (N=18), mild cognitive impairment (MCI, N=24), other causes of dementia (OD, N=26) and matched controls (OC, N=26) were tested, with closed eyes, for their ability to detect an odor, one nostril at a time. A container of 14g of peanut butter was opened, held medially at the bottom of a 30 cm ruler, and moved up 1cm at a time during the participants’ exhale. Upon odor detection, the distance between the subject’s nostril and container was measured.

> Results: The mean odor detection distance of AD patients’ left nostril (5.1 cm), and not their right (17.4 cm), was significantly less (F(3,90) = 22.28, p < 0.0001) than the other groups. The mean, standard error, and 95% Confidence Interval of the L R nostril odor detection difference (cm) for AD was −12.4 ±0.5, (−15.0, −9.8); for MCI was −1.9 ±1.2, (−4.2,0.4); for OD was 4.8 ±1.0, (2.6,6.9); and for OC was 0.0 ±1.4 (−2.2,2.1).

Tiny pilot study. Where are odds ratios? Where are the multiple measurements per patient?

Great.

But we'll also have machines that measure out the dosages. And possibly a few controls. Plus we'll have to adjust for folks that have an exceptional sense of smell. And come to think about it, we'll need to make sure we have baseline sensitivity levels at different ages to base the test result on. We'll have to account for folks that have sensitive sense of smells, which could be a large problem for controls. Not only that, but we'll need to check for signs of a stroke and the many other things that can cause one to lose one's sense of smell.

On second thought, I'm much more likely to support the more expensive test and hope they invent a simple blood test as it seems to narrow things down further.

We would also have to take into account simple cases of the flu or a cold.

Yet, as long as the errors are overwhelming at the false positive side, it can be used to reduce the number of the more expensive test.

Peanut butter is even cheaper than that -- 10 people can smell the same peanut butter but they can't fit in the same Pet scanner.

What..I can't... I am speechless.

How is this test methodology affected by phenomena like: https://en.wikipedia.org/wiki/Nasal_cycle

That's just the initial bill. I bet insurance gets this down to no more than a few hundred bucks, same as with MRI.