ACQ Vol 12 no 1 2010

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Motor speech disorders
42 ACQ Volume 12, Number 1 2010 ACQuiring knowledge in speech, language and hearing
Medical Research Council (NH&MRC) “Levels of Evidence”
is one such guide that provides a hierarchy from which the
different levels of scientific information can be evaluated (see
box 1). T his is the first of hopefully many future columns that
will provide a forum for discussing evidence based
practice (EBP) and its relevance to the practice of
speech pathology. The “What’s the evidence?” column is to
be coordinated by Jenny Harasty, Speech Pathology Australia
National Advisor for Research and Evidence Based Practice.
What’s the evidence? will feature in forthcoming editions of
ACQ, and will align with the identified theme of the journal. It is
anticipated that What’s the evidence? will provide a professional
forum for members to think about EBP and reflect on their
own clinical practice. In particular, the column will aim to:
• provide a professional forum for EBP discussion and
reflection;
• provide a framework for appraising topics and published
papers that relate to everyday clinical practice;
• provide an overview and appraisal of current best
evidence in the field, leading to a useable “clinical bottom
line” or recommendations for practice.
As an introduction to EBP, in this first column Jenny Harasty
provides an outline of what EBP is and what the steps
involved in incorporating the evidence into clinical practice
are. Please feel free to contact Jenny with your thoughts,
queries or reflections on issues raised in this column. Jenny
is particularly keen to hear from practitioners regarding
their experiences in relation to EBP and to provide practical
support and advice to practitioners as they attempt to
incorporate the best available evidence into their practice.
What is evidence based practice?
I was asked the other day what evidence based practice is.
Is it ensuring that we have documented all that we do? Well
no – that is accountability and while very important, it is not
evidence based practice. Is it having data or other evidence
that demonstrates the effectiveness of our treatment? No,
that is evaluation of our interventions. Again crucial, but not
evidence based practice. Evidence based practice is the
integration of clinical expertise and the best available
research and evidence into clinical interventions. Evidence
may be found in published peer-reviewed articles in scientific
journals and in verbal reviews at expert conferences and
workshops. Evidence based practice does not negate
clinical expertise and clinician judgement. However, it
emphasises that clinical expertise must be informed by the
best available evidence. The original definition of EBP is from
the medical literature and says that:
Evidence based … [practice] is the conscientious,
explicit, and judicious use of current best evidence in
making decisions about the care of individual patients.
The practice of evidence based … [practice] means
integrating individual clinical expertise with the best
available external clinical evidence from systematic
research (Sackett et al., 1996, p. 71).
Evaluating the scientific evidence
Evaluating the evidence is easier than it used to be as there
are now many guides available. The National Health and
What’s the evidence?
Jenny Harasty
Box 1. Levels of evidence
Level I Evidence obtained from a systematic review of all relevant
randomised controlled trials.
Level II Evidence obtained from at least one well-designed
randomised controlled trial.
Level III Evidence obtained from well-designed controlled trials
without randomisation.
Evidence obtained from well-designed cohort or case
control analytic studies, preferably from more than one
centre or research group.
Evidence obtained from multiple time series, with or
without the intervention. Dramatic results in uncontrolled
experiments.
Level IV Opinion of respected authorities, based on clinical
experience, descriptive studies, or reports of expert
committees.
Source: NH&MRC:
publications/synopses/cp30.pdf
As shown in box 1, the highest level of evidence (Level
I) is considered to be a systematic review of a number
of randomised double-blind placebo controlled trials.
In a randomised control trial, participants are randomly
assigned to either a placebo group (which receives some
form of intervention that does not include the intervention
being evaluated), or a treatment group (that receives the
intervention being evaluated). Outcome data from both
groups are collected and analysed. “Double blind” means
that neither the participants nor the researchers know
which group the participants were in until after the data are
collected/analysed. A systematic review is a review of all the
randomised control trials published in an area and makes a
general finding based upon their group results, using specific
meta-analytic statistics (see
statmeta.html).
While systematic reviews of randomised controlled
trials are said to be the gold standard in medical research
(Greenhalgh, 2001), it is important to acknowledge that
this type of research design will not be appropriate for all
research studies (see Greenhalgh, 2001, p. 47). Indeed,
many important and valid studies in the field of qualitative
research do not feature the hierarchy of evidence as outlined
above. For this reason, it is important that clinical practice
be informed by information obtained from different sources,
including research projects that incorporate other levels of
evidence such as controlled trials without blinding or random
allocation, cohort studies, cross sectional surveys and single
case designs. Readers interested in finding out more about
these research designs are encouraged to refer to Dollaghan
(2007) and Greenhalgh (2001).
Jenny Harasty