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Published on 1 June 2002

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Evidence – how should we assess it?

Chris Cairns,
Editor

There is no doubt that healthcare treatment decisions should be based on the best available evidence. The introduction of many treatments we accept as standard was based on the results of large, well-designed multicentre randomised clinical trials (RCTs). The RCT is widely accepted as the gold standard in providing the evidence to underpin the use of new therapies.

However, RCTs are expensive and take a significant amount of time to carry out. Well-designed trials require a lot of planning time to ensure they are just that – well designed. The next barrier is the “signing up” of a number of centres to carry out the work. A subsequent delay will occur as ethics approval is obtained. Then patient recruitment must occur so that the study can be done. Even a centre with a large cohort of patients with the disease being studied will not be able to recruit and start them on the trial instantly. Some trials require participants to have suffered an acute episode like a myocardial infarction (MI), so recruitment will be dependent on patients suffering these conditions. Then follow the study period, analysis and subsequent publication.

What do we do in the meantime? Do we wait for the results of the large trials to be published, do we act on interim results from conferences, or do we accept the initial but scientifically limited results from the drug company’s initial work? The latter shows that the drug works and gives us a safety profile, but rarely gives us robust data to compare with the products already on the market. Many countries undertake some form of cost–benefit analysis, either linked to the registration process or in the postlicensing period. These can inform decision-making, but again the data can be limited and not comparative. A second question arises from the results. When the RCT shows a dramatic benefit or improvement from a drug that costs the same or less as other products, then the argument for adoption is indisputable, as is the case where it is shown to be less effective. But what do we do when the drug is only marginally better, albeit statistically significant, but is considerably more expensive, is difficult to use or has a small increase in the likelihood of serious side-effects?

Critical appraisal of the available evidence is obviously the principal tool, but it must be a dynamic process. As new evidence becomes available then the appraisal may change – remember, early trials of thrombolysis showed no statistical benefit due to the small numbers involved, and it was only when meta-analysis of a number of small and large trials was done that the benefits appeared. Clinical judgment is necessary when the evidence is not complete or there is a lack of robustness. Professional and clinical judgment is also needed to balance issues like increased efficacy against increased cost or toxicity.

Often the hospital pharmacist or clinical pharmacologist is the best person to do this. Not only do they have the requisite skills and scientific approach, but the fact they are not directly involved in the management of the individual patient means that an unrestrained view can be taken. Making these judgments is not easy, but it is a role that must be taken on. Pharmaceutical care skills apply to medicines policy as well as the management of individual patients.

Chris Cairns, Editor



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