Introduction

Physicians and other health workers have always claimed specialknowledge about what works – from this springs their legitimacy.Those outside the health professions have harboured more cynicalthoughts. Benjamin Franklin said that “God heals, and the doctortakes the fees” (Tripp, 1973), and George Bernard Shaw castigatedthe medical profession for being “no more scientific than theirtailors” (Shaw, 1911). However, until recent years healthcare hasbeen characterised not by uncertainty about efficacy but by an oftenunwarranted surety of therapeutic success. For many doctors it is acase of “not so much that they don't know, but that they know somuch that ain't so” (source unknown). More recently, the presence ofuncertainty has been made explicit and healthcare workers (and manydoctors in particular) have striven to become more‘evidencebased’.

Healthcare may be delivered by individual practitioners but they doso largely within the context of various national organisationalstructures. In the United Kingdom, the National Health Service hasthree main goals:

• • to promote good health

• • to diagnose and treat illness

• • to provide healthcare for those in continuing needs (TheScottish Office, 1991).

Tellingly, these goals are qualified with the caveat ‘within theresources available’ (The Scottish Office, 1991). Thus, evidence oneffectiveness is not simply the domain of healthcare practitioners.Managers and policy makers also need evidence to allow them toallocate resources, assess progress in meeting organisationalobjectives and manage performance.

This review of evidence in healthcare first describes the nature ofevidence and the commonly accepted methodologies for deciding whatworks, before explicating some of the themes aimed at ensuring thatthe evidence impacts on healthcare policy, health service managementand, most especially, clinical practice. It focuses primarily onevidence relating to effectiveness, and is largely confined toexploring how evidence is used in health service delivery. This isnot to suggest that healthcare is the only (or even the prime) routeto health, and recent work to develop evidence for public healthshows that the themes in this chapter are beginning to be addressedoutside of clinical services (Gowman and Coote, 2000).

Nature of evidence

Confidence in therapeutic effect has traditionally arisen frompersonal experience. Case reports and case series are “the age-oldcornerstone of medical progress” (Anonymous, 1990).