01-06-2009, 08:28 PM
A recent study was conducted to evaluate the efficacy of
a new drug for preventing hospitalization from pneumonia
associated with HIV-positive people. After
obtaining the appropriate consents, researchers used
patient records of participating physicians to identify a
group of HIV-positive patients who received the drug
in the year preceding the observation period. A second
group of HIV-positive patients who had not received
the drug were also identified in these same records.
Both groups were followed for a 1-year period to determine
the number of hospitalizations and number of
deaths due to all causes. The number of hospitalizations
for the group given the drug was significantly lower
than for the group not given the drug. However, the
mortality rate from all causes was found to be significantly
higher in the group who received the drug.
Because of this differential mortality rate, the physician
conducting this study concluded that this drug should
not be given to HIV-positive patients. The conclusion is
most likely which of the following?
(A) Invalid because knowledge of whether the patient
had received the drug or not biased the measurement
of the outcome variable
(B) Invalid because of the presence of the Hawthorne
effect
© Invalid because physicians participating in the
study may not have been representative of all
physicians who treat HIV-positive patients
(D) Invalid because the patients who received the drug
may have been less healthy than those who did not
(E) Valid for the population under study
a new drug for preventing hospitalization from pneumonia
associated with HIV-positive people. After
obtaining the appropriate consents, researchers used
patient records of participating physicians to identify a
group of HIV-positive patients who received the drug
in the year preceding the observation period. A second
group of HIV-positive patients who had not received
the drug were also identified in these same records.
Both groups were followed for a 1-year period to determine
the number of hospitalizations and number of
deaths due to all causes. The number of hospitalizations
for the group given the drug was significantly lower
than for the group not given the drug. However, the
mortality rate from all causes was found to be significantly
higher in the group who received the drug.
Because of this differential mortality rate, the physician
conducting this study concluded that this drug should
not be given to HIV-positive patients. The conclusion is
most likely which of the following?
(A) Invalid because knowledge of whether the patient
had received the drug or not biased the measurement
of the outcome variable
(B) Invalid because of the presence of the Hawthorne
effect
© Invalid because physicians participating in the
study may not have been representative of all
physicians who treat HIV-positive patients
(D) Invalid because the patients who received the drug
may have been less healthy than those who did not
(E) Valid for the population under study