On 13/07/18 18:30, cesar yammine wrote:
> Hello everybody,
> I would like to know if anyone has experience with MA where the included
> studies have a before/after design.
I recall having met this kind of problems in a meta-analysis of
short-term beta2 agonist drugs in COPD,
http://www.ncbi.nlm.nih.gov/pubmed/10908502. The problem then was that
that there was a mix of parallel and cross-over studies, and in the
latter not all the only the SD of the effect difference was given.
You may look to the review to see what solution we used (it was quite
long ago), but as far as I remember it involved to "guess" a reasonable
correlation between the two measures and apply it to the SD of the
difference to obtain the two separate SD, assuming that they were equal.
It may look a bit adventurous, but in that case a reasonable estimate of
the correlation between the two measures (FEV1 before and after
treatment in the same subject) was easy to obtain from empirical data.
Piersante Sestini
> Should I use the the same approach as with RCTs where I compute for
> example raw or standardized means and their SDs along with sample sizes
> or should I compute the change or difference of the means ( mean of
> intervention - mean of baseline).
>
> Regards
>
> Kaissar Yammine, MD, MPH, PhD
> Head of the Foot and Hand Clinic
> Director of the Center for Evidence-Based Sport and Orthopedic Research
> Emirates Hospital
> Dubai, UAE
>
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