Introduction to Clinical Trials:
key points
i)
Definition of a
trial
A clinical trial is an experiment performed on human subjects to assess
the efficacy of a new treatment or procedure.
Key features of a randomized
concurrently controlled clinical trial (RCT) are that two (or more) groups
(the treatment groups) are compared,
and that the subjects are allocated to the treatment groups at random.
ii)
Historical
Background
Over many centuries new medical treatments have been advocated on the
basis of appeal to authority. Modern
scientific methods, in which empirical experiments are used to guide our
thinking, began to gather pace in the 17th century. However, there were only isolated attempts to
adopt this approach when assessing medical treatments. Only over the last 50 years has there been a
more systematic approach to the empirical assessment of medical treatments and
RCTs are central to this.
For further
information on the possibly apocryphal experiment with cannonballs performed by
Galileo, see http://www.endex.com/gf/buildings/ltpisa/ltpnews/physnews1.htm
iii)
Empirical method
and Statistics
RCTs seek to compare treatments empirically:
we give one group of patients one treatment, and another treatment to the other
group and then observe the differences between the groups. It is as simple as that. The complexities in the methods to be
discussed reflect the need to ensure that the differences between the groups
are genuine (i.e. not chance artefact) and are due to the treatment difference
between the groups (i.e. not due to some other, unintended difference). Statistics is central to both aspects of
trial methodology.
iv)
Ethical issues
Experimenting on human subjects is an enterprise that is surrounded by
substantial difficulties: what can and cannot be done must be guided by ethical
principles which protect the well-being of the patients at all times.