Hi, Nick
you may not look at the repeated test as an independend. By definition.
So, the calculations this way have no sense.
VVV
On 18.03.2016 20:00, Myles, Nickolas [PH] wrote:
> Hello everyone,
>
> I am wondering if this is true to assume that if the screening test is
> repeated for the same patient over the period of time it will diminish
> the false negative rate?
>
> Assuming, the FOBT test for colorectal cancer screening is 80%
> sensitive, then FN rate will be 20% (p=0.2). Assuming the tests are
> independent and the error is completely random, will repeated
> screening over one year with FOBT make it 0,2x0.2=0.04 (4%) and over the
> three years under 1% (0.2x0.2x0.2=0.008)? This many sound very bold, but
> does the repeat measures work that way? of will it stay the same 20%
> irrespective of the repeat measures?
>
> I am not talking about false positives, but the question can certainly
> be extended for FP as well.
>
> thank you, will appreciate your opinion or reference.
>
> Nick
>
Vasiliy V. Vlassov, MD
President, Society for Evidence Based Medicine (osdm.org)
e-mail: vlassov[a t]cochrane.ru
snail mail: P.O.Box 13 Moscow 109451 Russia
Phone Russia +7(965)2511021
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