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Clinical trials on trial: Ensure trials produce valuable results

Clinical trials are necessary in order to ensure drugs are safe andeffective, to guide prescribers and to help patients use drugs safelysaid Joel Lexchin, school of health policy and management, YorkUniversity, Toronto, Canada, at the “Clinical trials on trial”conference, organised by HAI Europe, that was held in Berlin on 21November 2008

by Nicola Cree

Clinical trials are necessary in order to ensure drugs are safe and effective, to guide prescribers and to help patients use drugs safely said Joel Lexchin, school of health policy and management, York University, Toronto, Canada, at the “Clinical trials on trial” conference, organised by HAI Europe, that was held in Berlin on 21 November 2008.

However, he added that if there are problems with clinical trials the information obtained from them can be compromised and ineffective drugs are allowed on to the market, that prescribers and patients can not use effectively.

A major problem with clinical trials said Anita Hardon, faculty of social and behavioural sciences, University of Amsterdam, Amsterdam, The Netherlands is that trial populations do not reflect those that take the drugs in practice.

An example, she said, is that most blood pressure trials take place in younger patients and are based on the reduction of the diastolic blood pressure, however, in practice, it is the over 50 years age group that suffers from high blood pressure, when a reduction in systolic blood pressure is more important.

Professor Hardon also expressed concern that trials are not diverse, with many not examining differences for age or ethnicity. She said that although there is representation in some trials, the data is often not analysed or in some cases where differences in data are found, they are often dismissed.

There is resistance to subgroup analysis, she said, because it increases the size of trial populations, lowers statistical power and impacts on cost. There are also problems including ethnic minorities in trials since there are issues with enrolment, many are lost to follow up and there are difficulties in translating questionnaires.

Joan-Ramon Laporte, Fundacio Institut Catala de Farmacologia, Barcelona, Spain gave the audience a list of questions that must be asked to ensure internal validity of clinical trials (see Panel).

Internal validity of trials

1. Did the control group receive optimal treatment?

2. Was the dose given to the control group adequate?

3. Was the sample size adequate to identify any relevant difference?

4. Did the published results refer to the primary variable?

5. Have the trial results been published?

6. Were the results presented as a relative risk reduction or an absolute risk reduction

Citing an angiotensin II antagonist trial as an example, he said that a control group must receive optimal treatment. In the trial, he said, the average age of patients was 66.7 years but the control group was given atenolol, a treatment that is not recommended for patients of this age.

It is also important to look at whether the trial results have deviated from the primary variable and if all the trial results were published, he said.

It is also important to consider the external validity of the trial Professor Laporte said. He said that compliance is often higher in clinical trials and patients in clinical trials often have fewer co-morbidities, which are not representative of clinical practice.

There is often publication bias in trials, he said, with trials showing a more favourable outcome more likely to be published.

Many people believe newer medicines to be better, Professor Hardon said but they need to be prepared to be sceptical about the newer. Professor Laporte said doctors should rely on older, well established drugs because there is often commercial pressure in clinical trials.

He said, that “commercial interest permeates all aspects of clinical research” and that clinical trials that are designed primarily in the interest of populations, not in the interest of selling drugs, are needed. Professor Hardon said that she believes that the funding for health research should come from taxes, not from companies.

Citation: The Pharmaceutical Journal URI: 10043449

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  • Anita Hardon: trial populations do not reflect those who use the drugs

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