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6: How were these clinical practice guidelines developed?

The Working Group conducted an exhaustive review and evaluation of the relevant scientific literature on prolonged fatigue, chronic fatigue and CFS. Although the working group recognised that CFS overlaps significantly with other fatigue-related syndromes, such as fibromyalgia or irritable bowel syndrome (see Part 2), the significance of these overlaps for pathophysiology and treatment is not clear. Hence, the Working Group focused on published studies whose principal topic was CFS.

The evidence contained within published studies was systematically evaluated according to the process outlined in the NHMRC Guidelines for the development and implementation of clinical practice guidelines (National Health and Medical Research Council 1995 - for a free copy, contact the NHMRC). Rankings were based upon scientific principles for comparison between published studies (Sackett 1996; Sackett 1994; National Health and Medical Research Council, 1995):

  • Genuine hypothesis testing requires use of appropriate research methodologies including collection of relevant control data, and suitable statistical analysis.
  • The interpretation of individual study findings may be constrained by factors such as whether the cohort examined was adequately representative of the patient population in general.
  • Replication across studies and in independent research centres is a key factor in the reliability of evidence.
The quality of evidence ratings chosen for these clinical practice guidelines were modified from existing guides (Sackett 1994; National Health and Medical Research Council, 1995). The amendments provided an integrated system for evaluating epidemiological and laboratory-based pathophysiological studies, as well as controlled treatment trials, as the former are not usually included in existing guides, which focus on treatment interventions.

Compelling evidence for clinical practice recommendations comes from consistent findings in two or more well-constructed, controlled trials or population-based epidemiological studies (i.e., Level I or Level II evidence; see inset "Quality of evidence ratings").

By contrast, clinical practice guidelines with Level IV evidence represent consensus statements of the expert panel, based upon clinical experience and limited scientific data. Although these statements may influence current practice, they are likely to be modified in response to further research findings.

Quality of evidence ratings

I
Consistent evidence obtained from more than two independent, randomised and controlled studies or from two independent, population-based epidemiological studies. Studies included here are characterised by sufficient statistical power, rigorous methodologies and inclusion of representative patient samples. Alternatively, a meta-analysis of smaller, well-characterised studies may support key findings.

II
Consistent evidence from two randomised controlled studies from independent centres, a single multicentre randomised controlled study or a population-based epidemiological study. Data included here have sufficient statistical power, rigorous methodologies and the inclusion of representative patient samples.

III-1
Consistent evidence obtained from two or more well-designed and controlled studies performed by a single research group.

III-2
Consistent evidence obtained from more than one study, but where such studies have methodological constraints, such as limited statistical power, or the inclusion of patient samples which may be non-representative.

III-3
Evidence obtained from a single case-control study or a selected cohort study.

III-4
Conflicting evidence obtained from two or more well-designed and controlled studies.

IV
Consensus opinions of respected authorities, based on clinical experience and/or descriptive reports.

 

  When the available evidence from several well-conducted studies on a particular topic was conflicting, the quality of evidence ranking indicated this uncertainty (Level III-4). However, when the overwhelming body of data was strongly in favour of one outcome, thereby negating a single conflicting study, the ranking chosen was Level I.

Data from a single case series without control subjects provide little more than a stimulus for subsequent hypothesis testing. Such reports were not included in the systematic analysis of evidence upon which these guidelines are based.

Next... Part 7: Bibliography

Chronic fatigue syndrome: Title page  Contents Send feedback
Draft Clinical Practice Guidelines on the evaluation of prolonged fatigue and the diagnosis and management of chronic fatigue syndrome
Version 1
December 1997
http://www.mja.com.au/public/guides/cfs/cfspart6.html
Published by The Medical Journal of Australia
©MJA 1997
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