Evidence of effectiveness alone is not enough for making decisions

Think about the decision of whether or not to use beta-interferon for people with multiple sclerosis. This is a relatively new drug for a condition which can progress, and for which few other treatments are available. Try to write down a list of all the factors that come into your mind when you are trying to make a health care decision like this.

Your list probably has many factors, among which will (hopefully) be evidence about whether the treatment improves the outcome for people with multiple sclerosis. But I imagine your list would probably include things like any special needs of the user, their priorities and values, as well as the available resources. You may have many other things on your list as well.

The key point is that research evidence is only one factor, albeit an important one, that needs to be taken into account during the decision- making process. Other types of evidence, such as the needs of the user, their priorities and values, as well as the available resources also need to be considered in the decision-making process.

It is not the job of the reviewer to try to weigh up all those factors, because a reviewer can never take account of all the variation in all the factors in the list in all the places that the review will be used. It is, however, possible to assist the user of your review in how to interpret and apply the evidence.

In the previous module we began the task of interpreting the results by considering the strength and relevance of the evidence. Even with this information the ultimate decision as to how to apply the evidence will be up to the users of the review. We need to remember that users of reviews will often come from very different settings around the world with very different circumstances and backgrounds. In this module we explore some of the other things that we can do to help users decide how to apply the evidence.

Identifying all the possible outcomes

A useful starting point is to identify all the outcomes that were considered in the review. These should have been listed with the inclusion criteria for studies in the review. It is often a good idea to have a further check that you haven't missed any important outcomes. For example, reviewers often unintentionally focus on the positive effects of treatment and forget the possible adverse effects.

In many reviews it may be important to consider the cost of treatment as one of the outcomes. Undertaking formal economic evaluations of the costs and benefits of an intervention are beyond the scope of the standard review. However, increasingly systematic reviews are being used as part of economic analyses.