How much do we know?
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 Clinical Evidence tell us about the state of our current knowledge? Figure 1 illustrates what percentage of the around 3000 treatments included in Clinical Evidence fall into each category. 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 that it is helpful, but like all tools it has benefits and limitations. For example, an intervention may have multiple indications and may be categorised as 'Unknown effectiveness' for one condition but 'Beneficial' for another. Included within the category of Unknown effectiveness are many treatments that come under the description of complementary medicine, for example, acupuncture for low back pain and echinacea for the common cold, but also many psychological, surgical, and medical interventions, such as CBT for depression in children, thermal balloon ablation for fibroids, and corticosteroids for wheezing in infants. The categorisation of Unknown effectiveness often reflects difficulties in conducting RCTs of an intervention and is also often applied to treatments for which the evidence base is still evolving. As such, these data reflect how treatments stand up in the light of evidence-based medicine and are not an audit of the extent to which treatments are used in practice.
We are continuing to make use of what is ‘unknown’ in Clinical Evidence by feeding back to the UK NHS Health Technology Assessment Programme (HTA) with a view to help inform the commissioning of primary research. Every 6 months we evaluate Clinical Evidence interventions categorised as Unknown effectiveness and submit those fitting the appropriate criteria to the HTA via their website http://www.ncchta.org/.