Introduction
We live in an era of evidence based medicine, where it is
expected that all clinicians should ensure their decision making is
informed by the best available scientific evidence. The development
of systematic reviews of randomized controlled trials of health
care has been promoted by The Cochrane Collaboration. Key
features of such reviews, as defined by the Cochrane collaboration,
are that they address a clearly formulated question, using
systematic and explicit methods to identify, select, and critically
appraise relevant research, and that they collect and analyze data
from the studies that are included in the review (1). Statistical methods such as
meta-analysis are an optional additional feature that can be used
to analyze and summarize the results of the included studies (1).
Systematic reviews have become increasingly important in health
care as they are seen as a key method for determining the value of
different diagnostic or management strategies and thus are able to
provide essential information to underpin the evidence based
approach. For example, systematic reviews are often heavily
cited to support recommendations contained within the ever
increasing number of clinical practice guidelines.
Systematic reviews also provide a straightforward method for
clinicians to keep up to date with their field (2), (3). Although highly valued by
clinicians and policymakers, it is noteworthy that the standard of
systematic reviews can vary and not all are high quality, for
example, many do not describe clear search strategies or
methodologies as recommended by PRISMA (4) or QUORUM guidelines (5).
High quality systematic reviews have proven valuable to
clinicians and policymakers alike, but still have a range of
important limitations. The most important limitation is that such
reviews have systematically excluded qualitative studies from the
evidence base thus making it difficult to understand the processes
at play when implementing complex interventions or the key issues
that will be important to their future integration into routine
practice. Such a crucial omission may be a factor
contributing to the difficulties so often seen in translating
"evidence" into practice. Thus even if a given complex
intervention is demonstrated to be "effective" in a particular
context there remains uncertainty about why and how it was
successful in that setting and the broad range of factors that
would need to exist in order to ensure successful implementation
and integration in other circumstances or contexts. Another
challenge, is that the exclusion of qualitative studies from the
systematic review process means that there are no clear mechanisms
for collating and interpreting qualitative data which is being
compiled in the same subject area, for example, patient experiences
of living with a specified chronic condition, in order to develop
conceptual models or gain a clearer picture of the problem under
investigation.
Consequently, in recent years there has been growing
interest in developing robust methods for synthesising qualitative
data ranging from narrative summary and thematic analysis through
meta-ethnography (6)
and realist synthesis (7). In this section we suggest that
NPT can provide a valuable method to aid the conduct and
interpretation of systematic reviews of a range of different types
of qualitative study and that there are three main ways in which it
could be used:
- To support the development of research questions and overall
design of a systematic review.
- To serve as a framework for data analysis within a systematic
review
- To support the interpretation of a systematic review's
results
Each of these is discussed in its own section; click on the
links above.
Things to consider
- What are the questions I am trying to answer by undertaking a
systematic review and how might NPT be of value?
- What kinds of research will or will not be amenable to this
type of systematic review?
References
- Green S, Higgins J
(2005) Glossary. Cochrane handbook for systematic reviews of
interventions 4.2.5. The Cochrane Collaboration. Available: http://www.cochrane.org/resources/glossary.htm
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- Oxman AD, Cook DJ,
Guyatt GH. Users' guides to the medical literature. VI. How to use
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- Swingler GH,
Volmink J, Ioannidis JP. Number of published systematic reviews and
global burden of disease: database analysis. BMJ
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- Moher D,
Liberati A, Tetzlaff J, Altman DG, for the PRISMA Group. Preferred
reporting items for systematic reviews and meta-analyses: the
PRISMA statement. BMJ 2009;339:b2535. Back to text
- Moher D,
Cook DJ, Eastwood S, Olkin I, Rennie D, Stroup DF, for the QUOROM
group. Improving the quality of reporting of meta-analysis of
randomized controlled trials: The QUOROM statement. Lancet
1999;354:1896-1900. Back to
text
- Dixon-Woods M, Agarwal S, Jones D,
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- Pawson R,
Greenhalgh T, Harvey G, Walshe K. Realist review - a new method of
systematic review designed for complex policy interventions.
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