Finding and appraising qualitative evidence
Bringing it all together for the benefit of patients and the public< Back to search results
- Format Texts
- Language/s English
- Target Audience Further education, Self-directed learning
- EBM Stage 4 - Decision making
- Duration <5 mins
- Difficulty Introductory
Key Concepts addressed
- 2-2a Reviews of fair comparisons should be systematic
- 2-2b All fair comparisons and outcomes should be reported
- 2-3b Relative measures of effects can be misleading
Improving reports of research and preparing and updating systematic reviews of reliable studies are essential foundations of effective health care.
Fair treatment comparisons avoid biases and reduce as far as possible the likelihood that users of research will be misled by the play of chance. These problems and their potential solutions have been discussed in earlier Explanatory Essays. However, even if the problems have been reduced as far as possible, health professionals, patients, policy makers and the public more generally may often find it difficult to make direct use of reports of research.
Often, this is because the quality of reports of research – whether individual studies or systematic reviews of them – leaves a great deal to be desired. Too often reports fail to provide important details about the design, conduct and analysis of research studies; adequate descriptions of who participated in them; what was done to participants; and what effects treatments had on outcome measures of importance to patients and others (EE 4.1 Altman 1994).
Very occasionally, a single well conducted and well reported study provides very strong evidence of the beneficial effects of an easily given treatment. For example, tens of thousands of people participated in a remarkable study that showed that an aspirin tablet could substantially reduce the risk of death among people who are experiencing heart attacks (ISIS-2 1988). It is very rare, however, that a single study provides such strong evidence. And it’s important when reading reports of individual studies to ask what other evidence – published and unpublished – is relevant. This is why systematic reviews of as high a proportion as possible of the relevant evidence are required to inform treatment and policy choices.
Systematic reviews are necessary, but they too, are insufficient for informing decisions about treatments for individual patients and policies. Other important factors – needs, resources and priorities – need to be taken into account. And this is the point at which the art as well as the science of health care needs to be deployed for the benefit of patients and the public (EE 4.3 Chalmers 1993; Rothwell 2007).
The text in these essays may be copied and used for non-commercial purposes on condition that explicit acknowledgement is made to The James Lind Library (www.jameslindlibrary.org).
Altman D (1994). The scandal of poor medical research. BMJ 308:283-284.
Chalmers I (1993). The Cochrane Collaboration: preparing, maintaining and disseminating systematic reviews of the effects of health care. In: Warren KS, Mosteller F, eds. Doing more good than harm: the evaluation of health care interventions. Annals of the New York Academy of Sciences 703:156-163.
ISIS-2 (second International Study of Infarct Survival) Collaborative Group (1988). Randomised trial of intravenous streptokinase, oral aspirin, both, or neither among 17 187 cases of suspected acute myocardial infarction: ISIS-2. Lancet 332:349–360
Rothwell P (2007). Treating individuals: from randomized controlled trials to personalized medicine. London: Lancet.