SeriesCan randomised trials inform clinical decisions about individual patients?
Section snippets
Generalising from trial evidence
Participants in clinical trials are seldom representative of the general population. With the exception of some pragmatic trials randomised at the level of health-service provider, participants in trials are usually healthier, younger, and of higher social status than the people to which the intervention is to be applied. Does it matter? In some cases it may not. There are many common conditions in general practice, from ear wax to plantar warts, for which the outcomes of trials are likely to
The precision of individual prediction
If the intervention is easy to replicate and the individual patient is sufficiently similar to the trial participants to make a difference in outcome seem unlikely, is this the solution to the question of generalisation? For the clinician it is not, because most clinical trials display substantial heterogeneity of effect for individual patients. Few patients are satisfied to be told that the likelihood of a positive outcome is 20% in the intervention group and 5% in the control group or that
Implications for future research
The paradox of the clinical trial is that it is the best way to assess whether an intervention works, but is arguably the worst way to assess who will benefit from it. One response is to ask for more and larger clinical trials, stratified for all characteristics that might lead to heterogeneity of effect, so that trial evidence is available for every possible subgroup of patient. At the extreme position, it is a call for an infinite series of “n=1” trials. This approach is naive for three
Bridging the clinical evidence gap
The complexity of using evidence from clinical trials to make clinical decisions in general practice is not in dispute. Hart3 points to the complexity of social problems within which clinical problems arise and have to be solved, and concludes that most general practice depends on “interpreting personally unique patterns of illness, rather than recognising generalised patterns of disease”. Van Weel26 reports that more than 25% of patients aged older than 65 years present with significant
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