Home' Australian Pharmacist : Australian Pharmacist August 2013 Contents 68 Australian Pharmacist August 2013 I ©Pharmaceutical Society of Australia Ltd.
EVIDENCE BASED MEDICINE IN ACTION
By Dr Luke Bereznicki & Dr Ron Castelino
In previous articles we have provided an overview of the basics of
evidence-based medicine and reviewed common trial designs used in clinical
research, discussing their strengths and weaknesses.
In this article we will focus on systematic
reviews. High quality systematic reviews
are published in many of the leading
biomedical journals. They come at the top
of the hierarchy of evidence informing
evidence-based practice, and when well
conducted, provide the best estimate
of the effectiveness of a treatment or
intervention. However, it is important
to remember that any type of study
can be poorly conducted, leading to
invalid conclusions. This also applies
to systematic reviews, which collate
other studies and pool their outcomes.
The validity of their findings depends
to a large extent on the processes used
to identify, appraise and combine the
findings of primary research studies that
they include. If poor quality studies are
included, the result may be unreliable
(garbage in = garbage out).
What are systematic reviews?
A systematic review is a review of a clearly
formulated question that uses systematic
methods to identify, select and critically
appraise relevant research, and to collect
and analyse data from the studies that
are included in the review. Statistical
methods (meta-analysis) may or may
not be used to analyse and summarise
the results of the included studies.
Essentially, systematic reviews attempt
to bring the same level of rigor (and
elimination of bias) to providing a review
of the available evidence as is used in the
studies on which the review is based.
Reviews of scientific literature may range
from objective, quantitative information
syntheses of the best evidence to highly
subjective and selective summaries.
Systematic reviews are markedly
different, and far more time consuming
to develop, than traditional narrative
reviews or expert commentaries of
the research evidence. While reviews
written by experts are useful in providing
background to a topic, viewpoints or
expert opinions, they have several
Dr Luke Bereznicki is Acting Head of
School at the Tasmanian School of
Pharmacy. Dr Ron Castelino is a Lecturer
in Therapeutics and Pharmacy Practice
at the School of Pharmacy, University of
potential drawbacks. These include
• Reviews may be constructed to support
individual views, rather than providing
a balanced view of the literature;
• Selective inclusion of studies; and
• A lack of rigor around study selection,
assessment and integration of findings.
What are the critical features?
Systematic reviews attempt to access
and review systematically all of the
relevant articles in the field. A good
systematic review should explain the
research question well, outline the search
strategy and detail the designs of the
The steps involved in producing a
high-quality systematic review include:
• Identifying all relevant published and
• Selecting studies or reports
• Assessing the quality of each study
• Synthesising the findings from
individual studies or reports, and
• Interpreting the findings and
presenting a balanced summary of
the findings with consideration of any
The overall conclusions of a systematic
review are potentially more accurate and
reliable than those of individual studies.
Systematic reviews can be subject to a
variety of biases, such as:
• Bias in the selection of published
studies that are chosen for inclusion
(selection bias), or in the choice of
studies that are published in the first
place (publication bias);
• Bias in the level of importance
attributed to the study results by the
researcher conducting the systematic
• Bias in the way that results are
summarised and presented.
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