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PostPosted: November 5th, 2015, 9:28 am
by Buzznerd123
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Re: Testing paradox for rare diseases

PostPosted: November 5th, 2015, 10:59 am
by crotwich
Elementary statistics says c). 8) In 10000 people, less than 1 has the disease, but the test will produce approx. 100 false positives. Hence, the probability that a random positive actually has the disease is smaller than 1/100=1%.

BTW, welcome back Buzz! :)

Re: Testing paradox for rare diseases

PostPosted: November 9th, 2015, 2:15 pm
by Buzznerd123
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Re: Testing paradox for rare diseases

PostPosted: November 9th, 2015, 6:01 pm
by misterjuanperalta
So of the up to 14% of BFS'ers that developed MND (average over 45 years of age), how many false positives could there have been?

Re: Testing paradox for rare diseases

PostPosted: November 10th, 2015, 8:45 am
by crotwich
misterjuanperalta wrote:So of the up to 14% of BFS'ers that developed MND (average over 45 years of age), how many false positives could there have been?


No one can give you answer to tihs question and I have never seen a study which says that (up to) 14% of BFS'ers developed ALS/MND. Can you give us the reference?
Regarding these "progression studies", AFAIK:

1. There is a study written in Eisen-Krieger's book which says that within 258 ALS patients, 14% of them presented only with fasciculations. The mean time interval between developing fasciculation and other deficits was 7.6 months (range 3-11 mo).
viewtopic.php?f=4&t=21467&p=161687#p1616872 (5th post).

2. Earlier Eisen's study showed that 6.7% of his 312 ALS patients had fasciculation as an inital sypmtom. The mean time interval between developing fasciculation and other deficits was 7.2 months (range 2.4-13.6 mo). The authors of the original Mayo's wrote a reply, saying that this didn't match their experience, since all of their ALS patients who had fasciculation (as the first symptom) always had EMG abnormalities.
viewtopic.php?f=5&t=248&hilit=letter+eisen

Regarding these statistics, this is very far from saying that 6.7% or 14% pts who have fasciculations (let alone those already diagnosed with BFS) were diagnosed with ALS in the future (these studies were performed on ALS pts, not BFS pts). Moreover, in his recent reply to Little Lost, Eisen himself wrote that it is extraordinarily rare for ALS to truly present with fasciculations and (in his opinion) if after 8 months there are no other clinical features then it is not ALS. Go figure!
viewtopic.php?f=5&t=19728

Re: Testing paradox for rare diseases

PostPosted: November 10th, 2015, 10:12 am
by misterjuanperalta

Re: Testing paradox for rare diseases

PostPosted: November 10th, 2015, 10:38 am
by crotwich
misterjuanperalta wrote:My information comes from here: viewtopic.php?f=4&t=21295&p=160169&hilit=+Eisen#p160169


Then I suggest you reread that topic (as well as the original studies), since you are spreading the wrong information. There was NO study mentioned there that x% of BFS pts progressed to ALS. On the other hand, the world's best specialists told us that such an x is very small.

Re: Testing paradox for rare diseases

PostPosted: November 10th, 2015, 11:11 am
by misterjuanperalta
Great to know. Thank you for clearing it up. Funny how I get called out on the "wrong" information and get "silence" on the good information. Just saying.

Re: Testing paradox for rare diseases

PostPosted: November 10th, 2015, 2:00 pm
by crotwich
MJP, FWIW I am grateful for your contributions and I am glad you found a possible explanation of your symptoms.