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Old 08-05-2012
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Default Type of study?

A new drug with in vitro activity against HIV is tested on a population of patients with Western-blot confirmed HIV
infections. Out of the 200 individuals in the patient population, 100 individuals are chosen by lottery to receive
the drug. The drug, which is tasteless, is administered in a cup of orange juice; the other patients receive pure
orange juice. Neither the nurses, doctors, nor patients know which patients receive the drug. At the end of the
study period, the number of CD4+ T cells is determined for all of the subjects. This is an example of a


A. case-control study

B. case report

C. cohort study

D. cross-sectional study

E. double-blind randomized clinical trial
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Old 08-05-2012
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Quote:
Originally Posted by Novobiocin View Post
A new drug with in vitro activity against HIV is tested on a population of patients with Western-blot confirmed HIV
infections. Out of the 200 individuals in the patient population, 100 individuals are chosen by lottery to receive
the drug. The drug, which is tasteless, is administered in a cup of orange juice; the other patients receive pure
orange juice. Neither the nurses, doctors, nor patients know which patients receive the drug. At the end of the
study period, the number of CD4+ T cells is determined for all of the subjects. This is an example of a


A. case-control study

B. case report

C. cohort study

D. cross-sectional study

E. double-blind randomized clinical trial
E.............
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Old 08-05-2012
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Explanation:

The correct answer is E. This is an example of a placebo-controlled, double-blind randomized clinical trial. In
this type of study, subjects with a particular disorder are randomized (the lottery) to receive either the treatment
in question or a placebo. The information about whether the patient receives the treatment or the placebo is not
known to either the subject or the investigator (double-blind). This type of study may be used to infer causality,
i.e., if the patients taking the medication have more CD4+ T cells than the other group, it is due to the drug in
question.

A case-control study (choice A) is a retrospective study that pairs known cases of a disease with matched
controls. This type of study gives information about the importance of risk factors. The lack of a prospective
design makes inferences about causality difficult.

A case report (choice B) is a published report of a single incidence of a disease in a subject. This is usually
done for rare diseases, or for rare associations of a disease with a particular risk factor.

A cohort study (choice C) is an observational (non-interventional) study that tracks subjects prospectively. This
type of study gives a measure of incidence of a disease.

A cross-sectional study (choice D) samples at a selected point in time, matching individuals with the disease
with controls without the disease. The lack of a prospective design makes inferences about causality difficult.

Last edited by Novobiocin; 08-05-2012 at 03:15 PM.
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