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A comment on U.S. plans trial of early detection blood tests for multiple cancers. Parent comment

Re:U.S. plans trial of early detection blood tests for multi... by arcticbull on Thursday June 23, 2022 @02:38AM (#31845839)
Folks love the idea of doing something instead of doing nothing, even when doing nothing leads to better outcomes. Classic example is the prostate cancer PSA antigen test. It is not recommended in the UK and I believe is no longer recommended in the US. [1]

The problem with this kind of screening is even tests that are highly accurate in a population with a high incidence rate are super duper inaccurate when used against the general population. False positives often have significant consequences, including invasive tests and surgeries with their own risks. tl;dr Bayes' rule is a bitch. [2, 3] I doubt they've solved this problem - but I sure hope they have because why wouldn't I?!

> "A patient goes to see a doctor. The doctor performs a test with 99 percent reliability--that is, 99 percent of people who are sick test positive and 99 percent of the healthy people test negative. The doctor knows that only 1 percent of the people in the country are sick. Now the question is: if the patient tests positive, what are the chances the patient is sick? - The intuitive answer is 99 percent, but the correct answer is 50 percent...." [3]

[1] https://www.nhs.uk/conditions/prostate-cancer/should-i-have-...

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7082531/

[3] https://sphweb.bumc.bu.edu/otlt/mph-modules/bs/bs704_probabi...

[ Parent | on HN ]
Re:U.S. plans trial of early detection blood tests for multi... by FollowingTheDao on Thursday June 23, 2022 @08:02AM (#31847859)
Doing nothing, yes, that’s my motto.

This test would be a fear driven profit center for these companies. I don’t like them at all. Easy way to sell the test isn’t it? “You don’t want cancer do you?”

My father was diagnosed with pancreatic cancer. The doctors gave him six months to live. They said “if she goes on chemo will get a year”. Both myself and my sister-in-law who is in oncology nurse advised him not to go on chemo. But he did. He died a month after starting chemo because it caused his bile duct to clog and it shut down his liver.

Yeah, so doing nothing, that’s my motto.

[ Parent | on HN ]
Re:U.S. plans trial of early detection blood tests for multi... by adamredwoods on Thursday June 23, 2022 @03:10AM (#31846025)
Always get a second opinion for anything major.
[ Parent | on HN ]
Re:U.S. plans trial of early detection blood tests for multi... by arcticbull on Thursday June 23, 2022 @03:12AM (#31846037)
While good advice, in general, in the US, liability pushes doctors to act when they have any signal.
[ Parent | on HN ]
Re:U.S. plans trial of early detection blood tests for multi... by adamredwoods on Thursday June 23, 2022 @12:18PM (#31851250)
It can go both ways, there is liability in wrong diagnoses. But-- based on my experience, all the doctors have been quite thorough in any diagnoses. In terms of cancer, one area people sometimes miss is asking the pathologist for a second reading on the cells.
[ Parent | on HN ]
Re:U.S. plans trial of early detection blood tests for multi... by arcticbull on Thursday June 23, 2022 @12:55PM (#31851868)
Apologies, to be clear - I completely agree with you, and yes a second opinion especially in something as important as cancer is excellent advice.
[ Parent | on HN ]