How much do we know?
BMJ Clinical Evidence aims to help people make informed decisions about which treatments to use. It can also show where more research is needed. For clinicians and patients we wish to highlight treatments that work and for which the benefits outweigh the harms, especially those treatments that may currently be underused. We also wish to highlight treatments that do not work or for which the harms outweigh the benefits. For the research community our intention is to highlight gaps in the evidence, where there are currently no good RCTs or no RCTs that look at groups of people or at important patient outcomes.
So what can BMJ Clinical Evidence tell us about the state of our current knowledge? What proportion of commonly used treatments are supported by good evidence, what proportion should not be used or used only with caution, and how big are the gaps in our knowledge? Of around 2500 treatments covered 13% are rated as beneficial, 23% likely to be beneficial, 8% as trade off between benefits and harms, 6% unlikely to be beneficial, 4% likely to be ineffective or harmful, and 46%, the largest proportion, as unknown effectiveness (see figure 1). Dividing treatments into categories is never easy hence our reliance on our large team of experienced information specialists, editors, peer reviewers and expert authors. Categorisation always involves a degree of subjective judgement and is sometimes controversial. We do it because users tell us it is helpful, but judged by its own rules the categorisation is certainly of unknown effectiveness and may well have trade offs between benefits and harms. However, the figures above suggest that the research community has a large task ahead and that most decisions about treatments still rest on the individual judgements of clinicians and patients.