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Explanatory Versus Pragmatic Clinical Trials
One
of the most useful distinctions for the design of clinical
trials of all types was articulated by Schwartz
and Lellouch (1967), who characterized two different
purposes of clinical trials, which they call "explanatory"
and "pragmatic."
- An
"explanatory" approach seeks to elucidate a
biological principle. The study population is considered
to be a model from which one may learn principles of pharmacology
or physiology—principles that are likely to shed light
on a variety of clinical problems.
- A
"pragmatic" approach, in contrast, focuses on the
question, "What is the better treatment in the particular
clinical circumstances of the patients in the study?"
In reading
the analgesic literature, one can pick out both explanatory
and pragmatic traditions (Max,
1994). Early analgesic researchers such as Beecher and
Houde had a strong explanatory bent. They carried out single-dose
comparisons in patients with postoperative or cancer pain
(Houde et al., 1965; Houde
et al.,1966), claiming that these diseases provide a
"model" for analgesic efficacy in any pain condition,
and used the many control groups
described in Section 3 of
this chapter. These studies are the basis for modern analgesic
relative potency tables.
More
recently, groups of anesthesiologists have carried out series
of pragmatic studies evaluating the usefulness of techniques
such as patient-controlled anesthesia, epidural opioids
and anesthetics, and peripheral nerve blocks in surgery.
These investigators have illuminated the use of particular
techniques in specific clinical situations, but have been
less interested in issues such as assay
sensitivity that are essential for generalizing the
results of these studies to other clinical situations.
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