Admissible evidence
Authors: P. CROFT
Journal: Annals of the Rheumatic Diseases (1998)

Admissible evidenceAn article appeared recently in a journal for general practitioners, in which the author (a general practitioner) told the story of his own shoulder pain. 1 He had had some physiotherapy that made it feel better, and then had read a meta-analysis that said that physiotherapy was of no proven benefit for shoulder pain.His shoulder pain had recurred and he had had an injection that made it feel a lot better, and then had read a meta-analysis that concluded that there was little scientific basis for injecting the shoulder."Are we using the right sort of evidence?" he pleaded in desperation.Musculoskeletal doctors will recognise that plea.The GP had admittedly overinterpreted the meta-analyses because each one would have ended with the observation that "there have been too few randomised controlled trials of suYcient quality on which to base a judgement of eVectiveness".This does not mean that physiotherapy or shoulder injections are useless.The absence of evidence is a very diVerent aVair to having clear evidence that an intervention does not work.Why then will so many clinicians feel sympathy with the perplexed GP? If it moves, randomise itThe proponents of evidence-based medicine are careful to emphasise that all types of evidence are admissible in judging the most eVective and eYcient way to treat an individual patient. 2 However, the main manifestation of evidence-based medicine worldwide (the Cochrane Collaboration) gives primacy to evidence from randomised controlled trials.At a strictly scientific level this is fine: it is the closest we can come in the dirty reality of daily life to the paradigm of the laboratory experiment.By randomising we create groups of patients who do not diVer in any systematic way except for the one in which we are interested (the intervention).The comparison is thus focused on the intervention, uncluttered by the confounding factors that influence choice of treatment in practice.Cochrane's notion was that we could "RCT" anything. 3his leaves us with a few problems however.Firstly, in many fields of health care we are not very good at randomised controlled trials.That is the real conclusion of those meta-analyses of shoulder trials.An overview of systematic reviews in the whole field of soft tissue rheumatism would conclude that there are very rarely suYcient trials of good quality to produce a definite result.It is no coincidence that the great achievements of the randomised controlled trial have been in more clearcut diagnostic areas than musculoskeletal pain, when mortality or well defined morbidity are the outcomes, and when pharmaceutical or technological interventions are under scrutiny.The use of aspirin after heart attacks to prevent death and recurrence is a classic example. 4Things are more diYcult in the rheumatological field where diagnosis is uncertain, outcome non-specific, understanding poor, and the mechanism of many interventions unexplained.The sheer complexity of symptoms weighs against easy answers, and the "availability of evidence will vary enormously from specialty to specialty". 5 Secondly, the strongest influences on outcome in the field of muscloskeletal pain are often likely to be non-specific aspects of the consultation.The reduction in pain observed in placebo groups during trials of treatments is one example.At the moment many RCTs go forward on the basis that "we have these two treatments which have been around for a long time, let's randomise patients and on July 30, 2023 by guest.