Methods for the thematic synthesis of qualitative research in systematic reviews



BMC Medical Research Methodology 2008, 8:45
http://www.biomedcentral.com/1471-2288/8/45

in one setting are not applicable to others [32]. However,
the act of synthesis could be viewed as similar to the role
of a research user when reading a piece of qualitative
research and deciding how useful it is to their own situa-
tion. In the case of synthesis, reviewers translate themes
and concepts from one situation to another and can
always be checking that each transfer is valid and whether
there are any reasons that understandings gained in one
context might not be transferred to another. We attempted
to preserve context by providing structured summaries of
each study detailing aims, methods and methodological
quality, and setting and sample. This meant that readers of
our review were able to judge for themselves whether or
not the contexts of the studies the review contained were
similar to their own. In the synthesis we also checked
whether the emerging findings really were transferable
across different study contexts. For example, we tried
throughout the synthesis to distinguish between partici-
pants (e.g. boys and girls) where the primary research had
made an appropriate distinction. We then looked to see
whether some of our synthesis findings could be attrib-
uted to a particular group of children or setting. In the
event, we did not find any themes that belonged to a spe-
cific group, but another outcome of this process was a
realisation that the contextual information given in the
reports of studies was very restricted indeed. It was there-
fore difficult to make the best use of context in our synthe-
sis.

In checking that we were not translating concepts into sit-
uations where they did not belong, we were following a
principle that others have followed when using synthesis
methods to build grounded formal theory: that of ground-
ing a text in the context in which it was constructed. As
Margaret Kearney has noted
"the conditions under which
data were collected, analysis was done, findings were found,
and products were written for each contributing report should
be taken into consideration in developing a more generalized
and abstract model"
[[14], p1353]. Britten et al. [32] suggest
that it may be important to make a deliberate attempt to
include studies conducted across diverse settings to
achieve the higher level of abstraction that is aimed for in
a meta-ethnography.

Study quality and sensitivity analyses

We assessed the 'quality' of our studies with regard to the
degree to which they represented the views of their partic-
ipants. In doing this, we were locating the concept of
'quality' within the context of the purpose of our review -
children's views - and not necessarily the context of the
primary studies themselves. Our 'hierarchy of evidence',
therefore, did not prioritise the research design of studies
but emphasised the ability of the studies to answer our
review question. A traditional systematic review of con-
trolled trials would contain a quality assessment stage, the
purpose of which is to exclude studies that do not provide
a reliable answer to the review question. However, given
that there were no accepted - or empirically tested - meth-
ods for excluding qualitative studies from syntheses on
the basis of their quality [57,12,58], we included all stud-
ies regardless of their quality.

Nevertheless, our studies did differ according to the qual-
ity criteria they were assessed against and it was important
that we considered this in some way. In systematic reviews
of trials, 'sensitivity analyses' - analyses which test the
effect on the synthesis of including and excluding findings
from studies of differing quality - are often carried out.
Dixon-Woods
et al. [12] suggest that assessing the feasibil-
ity and worth of conducting sensitivity analyses within
syntheses of qualitative research should be an important
focus of synthesis methods work. After our thematic syn-
thesis was complete, we examined the relative contribu-
tions of studies to our final analytic themes and
recommendations for interventions. We found that the
poorer quality studies contributed comparatively little to
the synthesis and did not contain many unique themes;
the better studies, on the other hand, appeared to have
more developed analyses and contributed most to the
synthesis.

Conclusion

This paper has discussed the rationale for reviewing and
synthesising qualitative research in a systematic way and
has outlined one specific approach for doing this: the-
matic synthesis. While it is not the only method which
might be used - and we have discussed some of the other
options available - we present it here as a tested technique
that has worked in the systematic reviews in which it has
been employed.

We have observed that one of the key tasks in the synthesis
of qualitative research is the translation of concepts
between studies. While the activity of translating concepts
is usually undertaken in the few syntheses of qualitative
research that exist, there are few examples that specify the
detail of how this translation is actually carried out. The
example above shows how we achieved the translation of
concepts across studies through the use of line-by-line
coding, the organisation of these codes into descriptive
themes, and the generation of analytical themes through
the application of a higher level theoretical framework.
This paper therefore also demonstrates how the methods
and process of a thematic synthesis can be written up in a
transparent way.

This paper goes some way to addressing concerns regard-
ing the use of thematic analysis in research synthesis
raised by Dixon-Woods and colleagues who argue that the
approach can lack transparency due to a failure to distin-

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