Question

How theory can be used as a framework to guide evidence based practice?

Answer 1

evidence-based practice Is very important to improve the quality and cost-effectiveness of health promotion interventions.the role of theory in the context of evidence-based practiceis upmost important.It argues that empirical evidence alone is insufficient to direct practice, and that recourse to the explanatory and predictive capability of theory is essential to the design of both programmes and evaluations.

AThe evidence-based practice has been on the appropriate measurement of effectiveness. The role of theory Is crucial in evidence based practices. It is also noteworthy that guidelines on undertaking systematic reviews tend to side-step the issue. For many, theory is equated with a reductionist position, and therefore judged to be incompatible with both holism and empowerment—the central tenets of health promotion. However, the accumulation of empirical evidence about effectiveness is of limited value to the practitioner unless accompanied by general principles which might inform wider application. Without reference to these theoretical principles we risk being submerged by a post-modern morass of empirical evidence, which, on its own, can do little to guide practice. The `knowledge is contingent and contextual rather than universal, determinate and invariable'. This broader interpretation of theory is central to the discussion here. The purpose of theory is seen not as offering universal explanations or predictions, but rather as enhancing understanding of complex situations. Such understanding will inevitably need to be sensitive to specific contextual factors, and would necessarily draw on the experience of practitioners and communities.

The US National Cancer Institute's monograph Theory at a Glance distinguishes two types of theory of relevance to the health promotion planning cycle—explanatory theory and change theory. Explanatory theory sheds light on the nature of the problem and helps to identify the range of factors that the health promoter might seek to modify. In contrast, change theory informs the development and implementation of intervention strategies. Without a full, rational appraisal of the problem and possible solutions, interventions might easily:

• Address wrong or inappropriate variables (i.e. miss the target completely).

• Tackle only a proportion of the combination of variables required to have the desired effect (i.e. hit only a few of the total number of possible targets).

• Theory also provides the basis for judging whether all the necessary elements of a programme are in place. For example, a programme designed to encourage a particular behaviour, such as condom use, could not be expected to succeed unless it addressed the known determinants of that behaviour. Providing young people with information about condoms will have little effect unless they also have the skills to obtain and use condoms, they are able to be assertive in negotiating condom use with their partner, condoms are available, and so on. Theory can consequently make a major contribution to improving the design of programmes and maximizing potential effects.

• There are numerous theories to draw on. It would be invidious to attempt to provide a comprehensive list. Theories range from behaviour theory through change theory (at individual, organizational and community levels), to community development and policy theory. Reference has already been made to the National Cancer Institute's monograph. Nutbeam (Nutbeam, 1998) also provides a succinct overview. Any difficulty arises not so much from an insufficiency of theory, but rather the capacity to select relevant theory and apply it in practice.

reference to theory allows an assessment to be made of whether all the necessary elements of a programme are in place. In the context of evaluation, this type of analysis can be used to identify type III error, i.e. the rejection of the effectiveness of a programme when the programme itself was inadequate in terms of design or delivery. Clearly, programmes developed on an ad hocbasis—which we might refer to as the `suck it and see approach'—are extremely vulnerable to type III error.

It is undeniable that health promotion requires a strong evidence base. However, if this derives solely from the accumulation of empirical evidence of effectiveness, there is a very real danger of ending up with little more than a menu of proven interventions from which to select and without a rational base to guide that selection. Of more relevance to the practitioner are general principles together with an understanding of context-specific factors, which will allow adaptation to suit different situations.