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the case of medical trials, and potential side effects or adverse effects of the
therapy.
Phase II
: Investigators evaluate the intervention in a larger group of participants
in order to assess the effi cacy of the intervention in the targeted disease state.
During this phase, assessment of overall safety is continued.
Phase III
: Investigators evaluate the intervention in an even larger group of par-
ticipants and compare its performance to a reference standard, which is usually
the current standard of care for the targeted disease state. In general, this is the
fi nal study phase to be performed before seeking regulatory approval for the
intervention as is required depending on its type/nature.
Phase IV
: Investigators study the performance and safety of the intervention
after it has been approved and marketed. This type of study is performed in order
to detect long-term outcomes and effects of the intervention. It is often called
“post-market surveillance.”
The conduct of a Phase I, II or III clinical trial can be thought of in an operational
sense as consisting of three primary stages: (1) screening, (2) active monitoring and
(3) follow-up [
10
] (Fig.
6.2
). During the three stages, a specifi c temporal series of
processes is executed. First, potential participants must be screened to determine if
they meet the inclusion and exclusion criteria for the study (e.g., specifi c demo-
graphic and/or clinical parameters required for subjects to be eligible for the study).
Once a potential participant has been deemed eligible for the study, they are pro-
vided with an informed consent document, which must be signed prior to proceed-
ing with the enrollment process. 'Enrollment' in the context of clinical trials means
offi cially registering as a study participant, and is normally associated with the
assignment of a study-specifi c identifi er. Once a person agrees to become a partici-
pant, they are enrolled, and in the case of studies with multiple study groups or
arms, randomized into one of the study arms. In second stage of the trial, known as
active monitoring, the participant receives the intervention indicated by their study
arm and is actively monitored to enable the collection of study-specifi c data. This
intervention and active monitoring process is often iterative, involving multiple
cycles of intervention delivery and active monitoring. Finally, the follow-up phase
begins once a participant has completed the active monitoring stage of a study.
During this stage, subjects are contacted on a specifi ed temporal basis in order to
collect additional data of interest, such as long-term treatment effects, disease status
or survival status [
8
].
A clinical trial is usually described using a document called a
protocol
, which
contains background information, scientifi c goals, aims, hypotheses and research
questions to be addressed by the trial. In addition, the protocol describes policies,
procedures, and data collection or analysis requirements. A summary of tasks and
events that must occur during the active monitoring phase of a trial, known as the
study schema or calendar, is often included in the protocol document.
The quality of data produced by a clinical trial is assessed using multi-dimensional
metrics, which take into account the design, execution, analysis and dissemination
of the study results. The quality of a clinical trial is also judged with respect to the
signifi cance or relevance of the reported study results within a clinical context [
11
].
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