[RoboTeddy]

> a randomly screened individual with a positive test will only actually have a 12.8% chance of getting Alzheimers

Darmiyan folks, is this correct? If so, what are the implications for the utility of the test?

(No matter the answer it feels like this research is important -- thank you!)

[clfougner]

Darmyian founders wrote the following in another post[1]:

> Roughly 97% sensitivity (3% false negative) and 85% specificity (15% false positive)

So with this information, the calcuation of Bayesian probability is as follows:

    (0.97*0.016)/(0.97*0.016+0.15*0.984) = 0.095

So a 9.5% chance of actually getting Alzheimers within the following 15 years if Darmiyan's test is positive. I don't have much formal statistical training, so I'm all ears if I'm making a mistake in the calculation here.

They also write the following:

> False positive here is not real false positive, as the software is detecting abnormality in people who are still cognitively normal.

Which is a terrible excuse - abnormality is only clinically relevant if it leads to disease. By this logic I can create the world's greatest test for cancer simply by saying that every given individual has cancer (100% sensitivity), and if they don't have it yet, they do carry the genetic abnormalities that will lead to cancer eventually - no "real false positives", right? Simply saying that "sooner or later, our test will prove correct" is not good enough here.

Founders of Darmyian: I commend your efforts in this space as a tool for research, and can potentially be very valuable for clinical trials. However, offering it to consumers as a screening tool when there are no proven preventative measures is - in my opinion - completely unethical and comes across as an attempt at trying to profit off fear mongering.

    [1] https://news.ycombinator.com/item?id=15083617

[kvejdani]

Darmiyan's product is NOT a probabilistic risk assessment test, and is NOT intended for use by the general public. There are already too many tests in the market for risk assessment, which are just probability numbers. Darmiyan's product is a software for quantitative assessment of micro-structural abnormality (neurodegeneration) in every voxel of brain MRI. You can think of it as a quantitative virtual microscope. Our maps and reports are not intended for use by the general public. Once we receive FDA approval in about a year or so, the Darmiyan test (software analysis of brain MRI) has to be ordered by a physician and interpreted by a physician to assist in clinical diagnosis and intervention recommendations, if any. The guidelines on Darmiyan test indications and interpretations will be determined by the medical community.

[kevinwang]

I used an online Bayesian calculator, and can confirm that the math checks out