New Blood Test for Alzheimer Disease

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Tom.G
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Main Question or Discussion Point

The Journal of the American Medical Association (JAMA) today (7/28/2020) published an article on using presence of phospho-tau217 (p-tau217) in blood plasma to detect Alzheimers Disease. Over 80% specificity, and early results look like it could be predictive up to 20 years.

doi:10.1001/jama.2020.12134
or
https://jamanetwork.com/journals/jama/fullarticle/2768841

Cheers,
Tom
 
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  • #2
Ygggdrasil
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About 10% of people 65 or older has Alzheimer's, so in a population of 100, there will be 10 with Alzheimer's and 90 negatives. With 80% specificity, 18 of the negatives will test positive (false positive) versus the 10 true positives in the sample. Even with 100% sensitivity, screening the general population with a test that has 80% specificity would give close to a 1.8x as many false positives as true positives.
 
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berkeman
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Even with 100% sensitivity, screening the general population with a test that has 80% specificity would give close to a 1.8x as many false positives as true positives.
Yikes, that's not good.
 
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BillTre
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Your population of potential positives would be enriched for true positives by going from 0.1 to 0.55.
 
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jim mcnamara
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I think the assumption on testing like this is: early detection allows for early intervention. Pharmacology, life style changes, and diet are all considerations. There is no cure, just increased quality of life.
 

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