[LMB] Leaking

quietann quietann at gmail.com
Wed Jan 5 14:52:18 GMT 2022


I think you're trying to lead us into US politics once again (STOP IT,
WILLIAM), but I'll respond to the scientific part -- which is to say that
"accuracy" is complicated when it comes to genetic tests.

Testing for Tay-Sachs is a simple test, and recessive disease (need two
copies of the gene to be affected.) In a few Jewish communities, people
will be tested as they reach the age of marriage, and revealing "carrier
status" is part of the shidduch (matchmaking) to be sure that 2 carriers
don't marry each other. Simple recessive diseases like this (cystic
fibrosis is another example) have virtually error-free tests. Tay-Sachs is
a horrible horrible way to die. It is degenerative, and children affected
are usually dead by age 4, and their short lives are miserable. There is no
cure, and really no treatment to speak of. But I know what you want
to force on people.

The NIPT tests done in early pregnancy *do* have a high false positive rate
-- but in an ethical and legally unrestricted setting, further testing is
done. NIPT has high sensitivity (ability to detect abnormalities) but low
specificity (ability to detect "true negatives"), especially for
micro-deletions. It's sort of like mammograms -- what looks like an
abnormality isn't, most of the time, but further testing (repeat mammogram
or breast MRI, or a biopsy) is done before anything else. (And mammograms
do miss cancer sometimes -- they don't have as high sensitivity as NIPT.) I
worked for a maternal-fetal medicine service for a while; absolutely NO
decisions were made based on NIPT results alone, and the doctors
discouraged NIPT testing except in patients at high risk.

This is a good basic link for understanding sensitivity, specificity, etc.
https://www.healthnewsreview.org/toolkit/tips-for-understanding-studies/understanding-medical-tests-sensitivity-specificity-and-positive-predictive-value/

Ann

On Wed, Jan 5, 2022 at 8:41 AM WILLIAM A WENRICH <wawenri at msn.com> wrote:

> One of the things that bugs Gayle about me is that occasionally I will
> jump from one subject to another that has no or little connection to what
> has gone before. It's a little like Miles leaking thoughts when his mind is
> racing. (No, I'm not claiming to be like Miles in any important way.)
> As an example, I was reading an article about genetic testing that said
> that, while prenatal tests for Down's were fairly accurate, tests for other
> genetic problems could have up to 85% false positives. My mind immediately
> jumped to "The Yiddish Policemen's Union" and the test for Tay Sachs. The
> specific tests that were problematic were not mentioned in the article.
> Does anyone else's mind jump around like that?
>
> William A Wenrich
>
>   *   A sinner dependent on God’s grace.
>
> --
> Lois-Bujold mailing list message sent to quietann at gmail.com
> Lois-Bujold at lists.herald.co.uk
> http://lists.herald.co.uk/cgi-bin/mailman/listinfo/lois-bujold
>


-- 
quietann at gmail.com

aka "The Accidental Jewess"


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