Evaluating the Validity of a Therapy Study
The next step is to read the article and evaluate the study.
There are three basic questions that need to be
answered for every type of study:
This tutorial will focus on the first question:
are the results of the study valid? The issue of
validity speaks to the "truthfulness" of
the information. The validity criteria should
be applied before an extensive analysis of the study
data. If the study is not valid, the data may not
The evidence that supports the validity or truthfulness
of the information is found primarily in the study
methodology. Here is where the investigators address
the issue of bias, both conscious and unconscious.
Study methodologies such as randomization, blinding
and accounting for all patients help insure that
the study results are not overly influenced by the
investigators or the patients.
Evaluating the medical literature is a complex undertaking.
It is not the intention of this tutorial to downplay
that intellectual process or to make you an expert
on evaluating the evidence. This session will provide
you with some basic criteria and information to consider
when trying to decide if the study methodology is
sound. You will find that the answers to the questions
of validity may not always be clearly stated in the
article and that clinicians will have to make their
own judgments about the importance of each question.
Once you have determined that the study methodology
is valid, you must examine the results and their
applicability to the patient. Clinicians may have
additional concerns such as whether the study represented
patients similar to his/her patients, whether the study
covered the aspect of the problem that is most important
to the patient, or whether the study suggested a
clear and useful plan of action.
Note: The questions that we used to test
the validity of the evidence are adapted from work
done at McMaster University. See the References/Glossary
unit: 'Users' Guides to the Medical Literature.'
We now go to Validity Questions