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How does it work? of Clinical trials

Most clinical trials are based on a comparison of a new treatment against an existing treatment.  If there is no existing treatment, a placebo might be used (a placebo is a treatment that has no physical effect).  The effects of the placebo are used as a yardstick against which the new treatment can be measured.

Most trials are randomised; people involved in the trial are given a different treatment on a random basis.  This helps to reduce the effects of bias and makes the results of the trial more accurate.  Normally, if there are two types of treatment, people will be randomly split into two groups.  The group who get the standard or placebo treatment are called the ‘control group’.

Most trials work on the basis that people do not know what treatment they are receiving.  This is known as ‘blinding’ and helps to reduce the effect of bias.  Many people feel better if they think they are getting a better treatment, even if this isn’t the case.

In some cases, the medical staff who are organising the treatment will not know who is receiving which treatment.  If both the patients and the medical staff do not know who is receiving which treatment, this is known as a double-blind trial.

Blinding is usually easier when testing drug treatments, but it can be very difficult when testing other types of therapy or methods of caring for people.

The best-known type of clinical trial is the Randomised Controlled Trial or RCT.  This is known to be a reliable method for comparing treatment options.  There are several other types of clinical trials that are used where an RCT is not appropriate such as

  • case controlled studies – match patients with controls, then retrospectively find any differences
  • cohort studies – compare groups exposed to different factors, and
  • case studies.

A systematic review (also known as a meta-analysis) is where researchers take the data from several similar clinical trials and combine it to get more accurate results.  This is thought to be the most reliable type of research evidence on which to base decisions about treatment options.