Hi unfortunetly in my study there are only 2 RCTs published to demonstrate any reliable effect with a surgical procedure on a pathology (osteoarthritis).
The remaining are case series, which measure patient's MEAN outcome scores at 1year, 1-5 years , >5 years. Some don't publish SD. Others publish just median scores. The series all have the same pathology (osteoarthritis), but do not necessarily have the same patient characteristics - typical of case series and units wanting to present their results.
Can I pool these Mean patient outcome scores together at 1 year / 1-5 years / >5 years and calculate the total mean and present them in a forest plot?
Does it statistically make sense or am I comparing apples and oranges? Do I just calculate the average or are there any tests you would recommend?
I understand that is the limitation that this is poor literature and hard to come to a conculsion, but that is the point I am trying to highlight that we can't keep publishing small case series but need large registry data which I will be working on.
Lipsey and Wilson (2001) tells us that a missing standard deviation can be substituted with a standard deviation from a similar study which uses the same assessment instrument. Not certain if this will be helpful or not considering you only are able to locate 2 RCTs. Perhaps expand your search to include data from dissertations that included RCTs. You may also want to review the directives of Hedge's to ensure that pooling the means is a plausible decision.
Best of luck!
2 RCTs sound too small to perform a meta-analysis, but you could take a look at:
Article A comparison of methods for meta-analysis of a small number ...
I assumed included studies met your predetermined inclusion/exclusion criteria based on protocol. If so, in this case , I would contact author requesting some missing information that I need for meta analyais.
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