So, what is the correct way of calculating PPV/NPV for repeat tests?
thanks for reliable references if any
N
Nickolas Myles, MD, PhD, MSc, FRCPC
Anatomical pathologist, St.Paul’s Hospital,
Clinical Associate Professor, University of British Columbia
Department of Pathology and Laboratory Medicine
1081 Burrard St, Vancouver, BC, V6Z1Y6
Phone (604) 682-2344 x 66038
Email: [log in to unmask]
-----Original Message-----
From: vv vlassov [mailto:[log in to unmask]]
Sent: Friday, March 18, 2016 11:04 AM
To: Myles, Nickolas [PH]; [log in to unmask]
Subject: Re: will false negatives go down with the repeated same test?
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
Подпишись на новости на osdm.org
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