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One key metric used to assess clinical trial quality is
validity
, which can be defi ned
both internally and externally. Internal validity is defi ned as the minimization of
potential biases during the design and execution of the trial, while external validity
is the ability to generalize study results into clinical care [
11
]. The primary source
of internal validity problems are either the Hawthorne Effect (e.g., a scenario in
which the act of measuring a pheromone of interest serves to change the targeted
process or behavior) [
12
], or study bias, which Juni et al. have defi ned as falling into
four primary types [
11
]:
Selection bias
occurs when participants are enrolled or randomized in a study in
preferential manner.
Performance bias
, often found in open or single-blind trial designs, occurs
when therapies are provided to study participants in a preferential manner.
Detection bias
, usually found in open or single-blind trial designs, occurs when
knowledge regarding to which arm a participant has been assigned is allowed to
affect the interpretation of study outcomes.
Attrition bias
occurs when data is censored or otherwise removed from study
analyses due to the attrition of participants.
6.2.2
Extending the Clinical Study Paradigm to Achieve
Translational Aims
In order to extend the clinical study model described in Sect.
6.2.1
to achieve
broader and translational aims, it is usually necessary to extend and enhance the
clinical study design. Such extension and enhancement include the provision of cor-
relative aims and scientifi c activities both prior to the design and conduct of Phase I
clinical studies, as well as the creation of feedback mechanisms from Phase IV and/
or observational studies to inform novel hypotheses for testing in laboratory based
settings. Such additions to the model introduced in Sect.
6.2.1
are illustrated in
Fig.
6.3
and correspond to the conduct of “
Basic and Pre
-
Clinical Research
”
upstream of clinical studies, and the conduct of “
Pragmatic Research
” downstream
of clinical studies, as described below.
6.2.2.1
Basic and Pre-clinical Research
In this precursor phase to the design and conduct of clinical studies, laboratory-
based investigators explore the structural and functional bases for a given disease
state in order to identify causative or modifi able factors that may serve to inform
diagnostic and therapeutic strategies (referred to as clinical end-points in the remain-
der of this discussion). For those fi ndings that show the potential to lead to new or
improved clinical end-points, a process of pre-clinical research is then undertaken,
often using model organisms as a “test bed”, so as to determine the safety and
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