Dear Michael,
No - generally you can't get to LRs from the OR without additional info.
The relationship is:
OR = LR+ve / LR-ve
or
log OR = Log LR+ve - Log LR-ve
So the OR is "split" between the two LRs, but without more info you can't
know where the split has been made,
Cheers
Paul Glasziou
At 25/05/2004, Michael Gross wrote:
>Danesh et al published their analysis of the association of C-reactive
>protein and C.A.D. (NEJM 2004: 350;14 pp1387-97) and found it to be
>less strong that a previous series of studies and subsequent published
>quidelines. They suggest that CRP may not be a useful measurement even
>in intermediate risk people. I hoped to calculate the likelihood ratio
>from their charts so that I could apply it to the standard Framingham
>risk tables to obtain post-test probability and see for myself.
>However, their statistical analysis is only expressed in odds ratios
>after adjustments for coronary risk factors, etc. Is there any way to
>convert these OR to LR? Thanks....
> Michael Gross, MD, MPH
> Lycoming Medical Associates
> Hughesville, PA, USA
Paul Glasziou
Department of Primary Health Care &
Director, Centre for Evidence-Based Practice, Oxford
ph: 44-1865-227055 www.cebm.net
