EUROPEAN TISSUE REPAIR SOCIETY

EVIDENCE BASED PRACTICE

EVIDENCE BASED PRACTICE

EVIDENCE-BASED PRACTICE:
SOUND IN THEORY, WEAKER IN PRACTICE?

DURING the past twenty years a wealth of new information has spread throughout health care – under the umbrella title of ‘evidence-based practice’. This new approach seeks to summarise existing research and from these summaries develop new insights into the likely effectiveness of health care practices and interventions. One of the founding fathers of this new movement in health care evaluation was Professor Archibald Cochrane (1909–1988) whose philosophy included focusing attention upon those practices and interventions shown to be effective in soundly designed trials. In particular, data from randomised controlled trials (RCTs) should be used to guide the selection of interventions.¹ His work resulted in the development of the first database on perinatal trials and a systematic review of such studies was published.² From 1993 onwards, reviews of RCT data have been undertaken by an international collaboration of individuals who volunteer to conduct and maintain systematic reviews of health care interventions (the Cochrane Collaboration, found at www.cochrane.org).

Today there are many definitions of evidence-based practice; for example, the website maintained by the School of Health and Related Research at Sheffield, UK (http:// www.shef.ac.uk/~scharr/ir/def.html) lists twenty-one separate definitions! However, all are broadly consistent with the views of Sackett and colleagues³ who noted that ‘evidence- based medicine 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 medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research’. For many ‘the best available external clinical evidence’ translates as the findings of randomised controlled trials and ideally, where possible, meta-analyses of several RCTs that have compared similar interventions. Why has the focus been placed upon one research design, the randomised controlled trial? Moher and colleagues⁴ elegantly summarised the high internal validity of randomised controlled trials when they commented that the RCT can provide those judging the merits of an intervention with ‘the confidence that the trial design, conduct, analysis and presentation has minimised or avoided biases in its intervention comparisons’. However, while this theoretical stance appears to offer significant

significant benefits in terms of unbiased interpretation of the efficacy of any intervention, the execution of randomised controlled trials in wound care has in the past been some what less than ideal! These flaws can be illustrated within an ‘early’ report of a randomised controlled trial; for in the Old Testament book of Daniel (Chapter 1; vv 11–16, New International Version) it is reported how Daniel and three friends held in captivity within a Royal Palace asked their captors to ‘test us for ten days, he (Daniel) said. Give us vegetables to eat and water to drink. Then compare us with the young men who are eating the food of the royal court, and base your decision on how we look … When the time was up they looked healthier and stronger’. Within this short passage are many of the weaknesses of modern randomised controlled trials, for example:

• inadequate sample size (in this case n = 4)
• short follow-up after use of the intervention (ten days)
• non-random allocation to treatment arms
• non-blinded assessment of outcomes
• subjective assessment of outcomes (base your decision on how we look)
• poor description of control and concurrent interventions (compare us with the young men … eating the food of the royal court)

Many of these weaknesses are all too evident in wound care randomised controlled trials! For example, within the thirty-seven randomised controlled trials identified in a systematic review within the Cochrane Library⁵ that compare the effects of pressure-redistributing support surfaces, only in eight studies could one be confident that subjects had been randomly allocated to the compared interventions. Other weaknesses exist; in the same systematic review only eight reported any attempt to blind those recording skin outcomes to the intervention allocated to the patient, while an a priori sample size calculation was only reported in ten of the thirty-seven studies. One further weakness helps to illustrate the current performance of wound care RCTs. Where beds and mattresses had been used to help manage existing pressure ulcers, in only five of the eight studies were the baseline characteristics of the pressure ulcers reported. These study limitations are not restricted to comparisons of pressure-redistributing beds.

In other systematic reviews of the effects of wound care interventions^6,7 similar flaws are found in the majority of the studies described. For example, in Bradley and colleagues’ review of wound dressings, it was concluded that ‘the majority of trials were of poor quality’ with only 25% (n = 7) having randomisation of subjects and only one of the twenty-eight studies reporting an a priori sample size estimate.

Given the weak execution of most wound care randomised- controlled trials there is clearly scope for the research community to improve its performance of such studies. However, caution is also needed, for, if every research question is tackled within an RCT, we may fall foul of Fisher’s⁸ accusation of ‘methodological fascism’ in which advocates of evidence-based practice ‘organise their faith in science into tidy, hierarchical rules of evidence, with the RCT as the only path to truth’. These strong views should help to reinforce that not all research questions can neatly be answered using the randomised controlled trial. For example, how should we address the cost-effectiveness of an intervention? While cost and efficacy data are often collected in RCTs the strict inclusion and exclusion criteria may restrict the intervention’s use to a very limited clinical population. How will both the costs of its use (and the likely clinical outcomes) change as the intervention becomes available to a wider, more general patient population? Perhaps the randomised controlled trial may not be the most appropriate design for exploring the cost of an intervention in general use and prospective cohort studies may be more helpful when cost is the major outcome of interest?

Perhaps, given the strong focus upon the randomised controlled trial as the source of the ‘best available clinical evidence’, it is timely to reconsider that Sackett and colleagues³ expanded their definition of evidence-based medicine to stress that it ‘is not restricted to randomised trials and meta-analyses. It involves tracking down the best external evidence with which to answer our clinical questions.’ Further debate is required regarding the nature of the ‘best external evidence’ where randomised controlled trials may not be appropriate. There are also a number of other misconceptions regarding evidence-based practice; it is seen to be

• cost-cutting medicine,
• just a way of introducing computers into clinical practice,
• ‘cook book’ care restricting professional choice and judgement.

In reality evidence-based practice may increase costs by identifying the benefits of expensive interventions, while the accusation of ‘cook book’ care is partially unfair. In wound care we have such little firm evidence of an intervention’s efficacy or effectiveness that no strong recommendations as to the ‘best’ intervention are likely, so professional choice and judgement are unlikely to be strongly limited by evidence-based practice (at this time at least). However, where the results of evidence-based practice become incorporated within guidelines, then professional freedom may be limited by the perceived need for the organisation to minimise the risk of future litigation by following national guidelines.

The preceding comments upon guidelines reflect that evidence-based practice is only one part of the struggle to deliver high quality, effective care. The evidence from systematic reviews has to become part of accepted clinical guidelines, while there is a need for both educational support and change management to help make the guidelines flourish in daily practice. Finally, the effects of the evidence- based guidelines of the processes and outcomes of care must be monitored if the perceived value of the entire process of evidence-based practice is to demonstrate a positive impact on wound care.

1. Cochrane AL. Effectiveness and Efficiency. Random Reflections on Health Services. London: Nuffield Provincial Hospitals Trust, 1972. (Reprinted in 1989 in association with the BMJ, reprinted in 1999 for Nuffield Trust by the Royal Society of Medicine Press, London (ISBN 1 85315 394 X)).
2. Chalmers I, Enkin M, Keirse MJNC, (eds.) Effective care in pregnancy and childbirth. Oxford: Oxford University Press, 1989.
3. Sackett DL, Rosenberg WMC, Gray JAM, Haynes RB and Richardson WS. Evidence-based medicine: what it is and what it isn’t. BMJ 1996; 312: 71–72.
4. Moher D, Jadad AR and Tugwell P; Assessing the quality of randomized controlled trials: current issues and future directions. International Journal of Technology Assessment in Health Care. 1996; 12: 195–208.
5. Cullum N, Deeks J, Sheldon TA, Song F and Fletcher AW. Beds, mattresses and cushions for pressure sore prevention and treatment (Cochrane Review). In: The Cochrane Library, Issue 4, 2002. Oxford: Update Software.
6. Bradley M, Cullum N, Nelson EA, Petticrew M, Sheldon T and Torgerson D. Systematic reviews of wound care management: (2) Dressings and topical agents used in the healing of chronic wounds. Health Technol Assess 1999; 3 (17 Part 2).
7. Bradley M, Cullum N and Sheldon T. The debridement of chronic wounds: a systematic review. Health Technol Assess 1999; 3 (17, Part 1).
8. Fischer PM. A note to family medicine researchers. J Family Pract 1994; 39: 221–224.

Michael Clark PhD Patricia E Price PhD Wound Healing Research Unit University of Wales College of Medicine Cardiff, CF14 4UJ All correspondence to Dr Clark