Combining findings Combining findings from different from different

research research

The EBM workshopThe EBM workshop

A.A.Haghdoost, MD; PhD of A.A.Haghdoost, MD; PhD of EpidemiologyEpidemiology

Ahaghdoost@kmu.ac.irAhaghdoost@kmu.ac.ir

Qualitative versus quantitative approachQualitative versus quantitative approach

EBM workshop Combining evidences A.A.Haghdoost

Ratio

nal

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.

EBM workshop Combining evidences A.A.Haghdoost

Ratio

nal

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.

EBM workshop Combining evidences A.A.Haghdoost

Quantita

tive a

pp

roach

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

EBM workshop Combining evidences A.A.Haghdoost

Qualita

tive a

pp

roach

If studies measured different parameters, such as measurement of depression using different questioners

If someone would like to combine the findings of qualitative studies

EBM workshop Combining evidences A.A.Haghdoost

PureReplications

ConceptualReplications

Meta analysis Meta synthesis

EBM workshop Combining evidences A.A.Haghdoost

Gu

idelin

e

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

EBM workshop Combining evidences A.A.Haghdoost

Meta

synth

esis

• “Putting together” findings from qualitative studies

• A relatively vague and little known comparative method of synthesizing qualitative studies – for the “accumulation of knowledge”

EBM workshop Combining evidences A.A.Haghdoost

Meth

od

olo

gy o

f meta

-synth

esis

(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

EBM workshop Combining evidences A.A.Haghdoost

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

Meth

od

olo

gy o

f meta

-synth

esis

(2)

EBM workshop Combining evidences A.A.Haghdoost

Arg

um

en

ts in Fa

vor o

f Meta

-S

ynth

esis

• 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

EBM workshop Combining evidences A.A.Haghdoost

Arg

um

en

ts Ag

ain

st Qu

alita

tive

Meta

-synth

esis

• 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