Do I have to include a certain type of observational study [i.e. cross-sectional study, longitudinal study, cohort study (retrospective & prospective) and case-control study] or all of the stated four types of observational studies can be included (based on availability) for systematic reviews & meta-analysis?
Dear Asiful,
If the available studies are limited all of the observational studies you mentioned can be included.
In case of too many studies to be included you can limit your inclusion criteria. For example only cohort studies.
Best wishes,
Ramin
This depends on the availability of related studies on the literature. In case a good number of clinical trials were conducted on the same topic, then you should limit your inclusion criteria to clinical trials. You can exclude the low quality clinical trials.
dear asiful
it is better to use only RCT studies for having a good meta-analysis, but if you have not enogh related studies ,you can use another types of cohort studies but validity of you study decrease if you do that...please note that cross sectional stydies are not one type of observational studies.
Dear Dr. Koorosh,
My study type is not to evaluate interventions, therefore I am not considering any RCTs. But for my Cochrane systematic review, I have considered only RCTs.
According to wikipedia, cross-sectional study is also included as an observational study (https://en.wikipedia.org/wiki/Cross-sectional_study).
Anyways, your response is highly appreciated!
Thanks very much.
No one answer fit all purposes.
If you want to conduct a meta-, you have to consider use RCTs. But if you only conduct a systematic review, then any type of observational studies can be included.
However, there are different levels in the quality of your systematic review, Meta- seems best.
The best one is Randomized Controlled Trial (RCT), but you can do a systematic review and metanalysis with any group listed by you.
Randomised controlled trials or quasi Rcts would be the best for inclusion in SR and metaanalysis. Clear inclusion and exclusion criteria of type of studies needs to be outlined when you write your protocol and will help with Data extraction of the included studies. I found the Cochrnae group very helpful. They have many different groups that could help you.
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