Combining findings from different research The EBM workshop A.A.Haghdoost, MD; PhD of Epidemiology Qualitative versus quantitative approach

A.A.Haghdoost EBM workshopCombining evidences Rational Researchers used to think the aim of a single study was to decide if a given effect was "real" (statistically significant). But they put little faith in a single study of an effect, no matter how good the study and how statistically significant.

A.A.Haghdoost EBM workshopCombining evidences Rational Each study produces a different estimate of the magnitude. When many studies were done, someone would write a narrative (= qualitative) review trying to explain why the effect was/wasn't real in the studies. Or would carry out a study to estimate the magnitude of an effect with adequate precision using others ’ findings.

A.A.Haghdoost EBM workshopCombining evidences Quantitative approach Meta-analysis combines the effects from all studies to give an overall mean effect and other important statistics. The measured effects should be comparable and estimate a common quantity

A.A.Haghdoost EBM workshopCombining evidences Qualitative approach If studies measured different parameters, such as measurement of depression using different questioners If someone would like to combine the findings of qualitative studies

A.A.Haghdoost EBM workshopCombining evidences Pure Replications Conceptual Replications Meta analysisMeta synthesis

A.A.Haghdoost EBM workshopCombining evidences Guideline Clinical practice guidelines are recommendations for clinicians and consumers about optimal and appropriate care for specific clinical situations Nowadays, formal guideline are generated by using both qualitative and quantitative methods

A.A.Haghdoost EBM workshopCombining evidences Meta synthesis “ Putting together ” findings from qualitative studies A relatively vague and little known comparative method of synthesizing qualitative studies – for the “ accumulation of knowledge ”

A.A.Haghdoost EBM workshopCombining evidences Methodology of meta-synthesis (1) Systematic review?! Focus on search strategies, quality and aggregation “ A critical assessment and evaluation of research (not simply a summary) that attempts to address a focused clinical question using methods designed to reduce the likelihood of bias. ” Guyatt and Rennie 2002

A.A.Haghdoost EBM workshopCombining evidences Since the papers are usually extremely heterogeneous, you can group the articles into categories of similar domains. For each article, central themes should be extracted and common metaphors identified for the whole category. Content analysis and compare the similarity and differences between study findings Methodology of meta-synthesis (2)

A.A.Haghdoost EBM workshopCombining evidences Arguments in Favor of Meta- Synthesis Qualitative research may be endangered and marginalized by its failure to sum up or put together – and not be “ little islands of knowledge ” Need to compare findings and data – in the same topical area Need to extend beyond modernism to post modernism

A.A.Haghdoost EBM workshopCombining evidences Arguments Against Qualitative Meta-synthesis You can ’ t sum up poems or songs! Variations of method and underlying theoretical assumptions Diversity of practices Destroys the integrity of individual studies Thins our deep descriptions De-contextualizes material