Box 41 Declaration of Helsinki 2000 on choice of control arms

'The benefits, risks, burdens and effectiveness of a new method should be tested against those of the best current prophylactic, diagnostic and therapeutic methods. This does not exclude the use of placebo, or no treatment, where no proven prophylactic, diagnostic or therapeutic method exists.'

In general, a new therapy should be compared against best standard practice, as described in the 2000 revision of the Declaration of Helsinki (see Box 4.1 and http://www.wma.net/e/policy/17-c_e.html). To identify whether your control arm represents 'best standard therapy,' consider whether or not there is evidence from randomized trials to support or refute it (this may require a systematic review - see Chapter 11). Consider also whether it represents an international, or national standard. It goes without saying that to choose an inferior control arm with the intention of enhancing the apparent benefit to a new treatment is unethical. However, knowingly choosing as your control arm a therapy that has been shown to be inferior to another treatment may sometimes be justified if, for example, financial or practical reasons make the 'better' treatment of limited use.

There are occasions when the choice of control arm is not entirely straightforward and it is sometimes the case that no internationally agreed standard therapy exists. In this situation, trials addressing similar questions, but using different control arms, may produce conflicting results (see for example Box 4.2).

It may also be the case that two (or more) 'standard' therapies may be considered approximately equivalent with respect to efficacy, but with different centres preferring one over the other for reasons perhaps of cost, toxicity or local practicalities. Minor

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