The back story: about Clinical Evidence

Welcome to Clinical Evidence, a database showcasing the best available evidence on common clinical interventions.

Clinical Evidence is a new kind of decision-support resource for the evidence-based medicine (EBM) era.

Of course, we publish peer-reviewed systematic reviews of important clinical conditions; but Clinical Evidence is much more than a conventional journal. By integrating our reviews with the tools to explain what EBM is and how - and why - to practise it, we provide a unique support resource that provides the latest and most clinically relevant medical knowledge.

Clinical Evidence is neither a textbook of medicine nor a set of guidelines

Our systematic reviews summarise the current state of knowledge - and uncertainty - about the prevention and treatment of clinical conditions, based on thorough searches and appraisal of the literature. They don't tell you what to do: they just describe the best available evidence from systematic reviews, RCTs, and observational studies where appropriate. And, if there is no good evidence, we say so.

In the beginning...

When we started, Clinical Evidence set out specifically not to make recommendations: we felt it was difficult, maybe impossible, to give advice for every situation, because differences in patients' risks and preferences, and in the local availability of interventions, mean that those situations vary hugely. So, we said, we'll supply the evidence, you make the decisions.

Increasingly, though, we have been rethinking this position (as we constantly re-examine everything we do - we've never stopped changing). It's still true, for example, that Clinical Evidence should point out where evidence is lacking. But it's also true that just saying, sorry, there's no information, may not be much help.

So we're addressing this issue with ongoing initiatives, such as encouraging authors to use their expert knowledge and the current consensus positions in our Clinical Guide sections where evidence is weak - while keeping as close as feasible to what reliable evidence there is.

Not just What... but Why

Like other EBM resources, such as producers of guidelines, we look to answer the 'what' questions that doctors and patients ask. But what Clinical Evidence also looks at are the 'whys'; because, without those answers, patients can only be treated in the kind of authoritarian manner that was out of date two decades ago.

The 'why' questions describe the difficulty of achieving the complexity demanded of best clinical practice - where patient-centeredness and evidence-based practice intersect. Our challenge is to determine which 'why' questions matter most.

And for that we need your help.

We may never claim to know which is the 'best' antidepressant (assuming there ever is one), but we can hope to say why you might use one, what result to expect, and whether cognitive behavioural therapy may be as good, better, or not, as the case may be.

Our history

Clinical Evidence (CE to its friends) was created in 1999, and it has been evolving ever since - both in response to clinicians' changing needs and the latest EBM innovations.

Standing still has never been an option. We have convened an international advisory board, held focus groups of clinicians and patients, and adopted countless great ideas from our contributors.

However, throughout all this development, we have kept in mind a crucially pertinent equation set out by Slawson et al.[1]

"The usefulness of any source of information is equal to its relevance, multiplied by its validity, divided by the work required to extract the information."

With this always in mind, we aimed for high relevance, high validity, and low work for our readers. We also stuck to basic principles of transparency and explicitness: readers needed to understand where our information came from and how it was assembled.

A unique resource

Clinical Evidence is one of a growing number of sources of evidence-based information for clinicians. But several features distinguish it from the others.

Principally, our content is driven by questions rather than by the availability of research evidence. So, rather than starting with the evidence and just summarising it, we first identify the key clinical questions. Then we search for and summarise the best available evidence to answer them.

CE identifies but does not try to fill important gaps in the evidence. In a phrase used by Jerry Osheroff, who has led much of the research on clinicians' information needs:[2]

"Clinical Evidence presents the dark as well as the light side of the moon."

It is important for clinicians to know when their uncertainty stems from gaps in the evidence rather than gaps in their own knowledge.


Clinical Evidence is currently available in three formats: in print (Clinical Evidence handbook); via PDA; and online. All the formats have been repeatedly redesigned and improved in response to user feedback, and we're always working hard on new enhancements.

As a result, CE is more usable than ever: live links to guidelines and related reviews, as well as book-quality PDFs of all our systematic reviews, are just some of the features that have kept it ahead of the rest.

Whichever the format, though, accessing the kind of complex information contained in CE can be tricky, even for experienced users. We're therefore working on making the text more readable.

For example, in many of our reviews we decided to try presenting the numbers in simple data tables rather than in the running text - and it has proved so popular that we're going to change all of them.

We've also encouraged more use of expert commentary to highlight the key clinical messages. We want your views on other ways in which we can make the information as accessible as possible.


  1. Slawson DC, Shaughnessy AF, Bennett JH. Becoming a medical information master: feeling good about not knowing everything. J Fam Pract 1994;38:505-513.
  2. Ely JW, Osheroff JA, Ebell MJ, et al. Analysis of questions asked by family doctors regarding patient care. BMJ 1999;319:358-361.