Observational research in the evidence based environment: eclipsed by the randomised controlled trial?
- Correspondence to:
Dr Rod H Stables, Royal Liverpool University Hospital, Prescot Street, Liverpool L7 8XP, UK;
- ARTS, arterial revascularisation therapy study
- CABG, coronary artery bypass graft
- NICE, National Institute of Clinical Evidence
- PTCA, percutaneous transluminal coronary angioplasty
- RCT, randomised controlled trial
- SoS, stent or surgery
Observational research plays an important role in hypothesis generation, establishing questions for future randomised controlled trials and defining the clinical conditions under which they will be addressed.
Patient based measures of outcome are assuming an increasing importance in the evaluation of therapeutic intervention. A classic, theoretical example of the importance of this approach involves the reporting of trials evaluating surgical procedures for benign prostatic obstruction. High quality studies might report significant improvements in appropriate outcome measures, such as the urinary flow rate or frequency of nocturia, and establish an apparent superiority over conservative treatment. When, however, patient satisfaction is considered, a side effect of erectile impotence in the surgical group may reverse this position.
A number of instruments have been developed for the quantitative assessment of what is now often referred to as “quality of life”. These may be generic, examining several aspects or dimensions of physical function and perceived well being. Others are disease specific with, for example, the Seattle Angina Questionnaire and the Cardiac Health Profile representing leading instruments in the assessment of angina pectoris.1
CABG VERSUS PTCA TRIALS
The first generation of trials comparing revascularisation by coronary artery bypass grafting (CABG) or percutaneous transluminal coronary angioplasty (PTCA) did not demonstrate any significant differences in the subsequent incidence of death or non-fatal myocardial infarction. Initial treatment with coronary angioplasty was, however, associated with a less complete resolution of angina at short term follow up and with a 10 fold increase in the requirement for additional, repeat revascularisation.2 An understanding of the impact of these findings on patient physical function and perceived heath state is essential if the relative merits of the two strategies are to be appreciated. A patient with stable angina contemplating elective revascularisation will be influenced by many factors and the reduced immediate procedural morbidity, shorter hospital stay, …