Volume 197 - Issue 7
General practice trials: the importance of creating evidence
Author: Mark R Nelson
Med J Aust 2012; 197 (7): 363-364. || doi: 10.5694/mja12.11216
Published online: 1 October 2012
Published online: 1 October 2012
Two studies testing interventions that made little difference to patient outcomes demonstrate the importance of translational researchGeneral practitioners are often expected to implement findings of clinical trials done in hospitals or academia. Health policymakers also develop and implement primary health care system changes without proper evaluation or being informed by translational research studies. Two clinical trials reported in this issue of the Journal give us ...
Two studies testing interventions that made little difference to patient outcomes demonstrate the importance of translational research
General practitioners are often expected to implement findings of clinical trials done in hospitals or academia. Health policymakers also develop and implement primary health care system changes without proper evaluation or being informed by translational research studies. Two clinical trials reported in this issue of the Journal give us three important lessons why this should not happen.1,2
First, good study design gives robust results. In a well designed and adequately powered clinical trial, a negative result is just as enlightening as a positive. Unless a new intervention is cheaper or more efficient — and they rarely are — it tells you what you should not be doing rather than what you should. However, often, although not in this case, a negative trial is subject to publication bias, as editors are loath to include it in their journal irrespective of its methodological rigour.
Both trials used a cluster randomised controlled study design, which is the method of choice where interventions are by nature open and, therefore, contamination is likely. Participants were randomly allocated by groups rather than as individuals. Although Harris and colleagues showed one small positive result of the intervention they tested (a sustained increase in self-reported physical activity), both trials were essentially negative.1 However, because of their design we can still learn from them. In Zwar and colleagues’ study, disease misclassification for chronic obstructive pulmonary disease (COPD) among participants was a problematic finding.2 The 42% misclassification rate they reported for south-western Sydney is similar to a contemporaneous finding of 31% for Tasmania, and is therefore likely to be both valid and generalisable.3 Thus, although the investigators may be criticised for not having an objective diagnostic inclusion criterion for COPD, implementation of the mooted partnership model of care would have been made on this clinical diagnosis basis and is likely to have been confounded by it. In a “learn to walk before you run” scenario, this observation means that general practice needs more rigorous and less presumptive diagnostic classification of COPD (ie, more widespread use of spirometry). The use of an intention-to-treat analysis preserved this finding, as a per-protocol analysis would have looked at outcomes based on clinical diagnosis.
The second lesson is that trial outcomes are best applied in the population in which they were conducted. Generalisability, the ability to apply clinical trial results in a given patient population, is greatest when the characteristics of trial participants are most like the patient population under consideration. It is therefore logical to conduct such trials in these populations. Underwriting this is the need to understand the environment in which the research is conducted. When non-GP researchers attempt to conduct studies among general practice patients, they may fail because of a lack of experience in the primary care environment. Both groups of authors are experienced primary care research teams. Harris et al took a pragmatic approach that fits with the existing enhanced primary care item number regimen, and involved a representative sample of at-risk general practice patients aged 40–64 years in whom it would be possible to influence behaviours and clinical outcomes.1 This suggests that findings can be practically applied. Their finding of a sustained increase in physical activity in the intervention group is likely to be beneficial on an individual and population basis owing to broader health benefits, as their study had a single disease focus, although it would have been better to have a more robust measure of physical activity than self-report. These findings also give some comfort to us on the benefit of referral to an exercise physiologist.
The third important lesson from these two studies is that, given sufficient resources, multicentre clinical trials can be conducted in general practices, even though they are often described as a difficult environment in which to conduct research. The completion of these two trials involving a total of 74 practices indicates that such trials are pragmatic but require significant resources to support them. Zwar et al’s study ran for 2.5 years in 44 of these practices and involved 451 participants — only 28% of the practices and 21% of the GPs who were approached. Through our experience with the Second Australian National Blood Pressure (ANBP2) and Aspirin in Reducing Events in the Elderly (ASPREE) studies, my colleagues and I also showed that, with appropriate resources, general practice clinical trials can be done on an internationally competitive large scale.4,5 ANBP2 involved 1594 general practices and 2681 GPs by study completion.6 ASPREE to date has involved 756 practices and 1729 GPs (unpublished data). These are extraordinary figures, given our reliance on goodwill towards “public good” research from what are, in the main, small, private businesses. This represents the underlying goodwill and professionalism of GPs and general practice.
Access for primary care researchers to a national practice-based research network has been long called for and is long overdue.7 Such a network could enable huge savings in recruitment time, money and other inputs and facilitate this very important area of research.
Competing interests
No relevant disclosures.
References
- Harris MF, Fanaian M, Jayasinghe UW, et al. A cluster randomised controlled trial of vascular risk factor management in general practice. Med J Aust 2012; 197: 387-393. 0_i1139880
- Zwar NA, Hermiz O, Comino E, et al. Care of patients with a diagnosis of chronic obstructive pulmonary disease: a cluster randomised controlled trial. Med J Aust 2012; 197: 394-398. 0_i1139882
- Walters JA, Walters EH, Nelson M, et al. Factors associated with misdiagnosis of COPD in primary care. Prim Care Respir J 2011; 20: 396-402. 0_i1139884
- Wing LMH, Reid CM, Ryan P, et al. A comparison of outcomes with angiotensin-converting-enzyme inhibitors and diuretics for hypertension in the elderly. N Engl J Med 2003; 348: 583-592. 0_i1139886
- Nelson MR, Reid CM, Ames DJ, et al; the ASPREE Investigators Group. Feasibility of conducting a primary prevention trial of low-dose aspirin for major adverse events in the elderly in Australia. Aspirin in Reducing Events in the Elderly (ASPREE). Med J Aust 2008; 189: 105-109. 0_i1139888
- Nelson M. High blood pressure research in Australian general practice [editorial]. Aust Fam Physician 2003; 32: 277. 0_i1139890
- Gunn J. Should Australia develop primary care research networks? Med J Aust 2002; 177: 63-66. 0_i1139893
Provenance: Commissioned; externally peer reviewed.