Part I: If the criteria for determining what constitutes a positive screening test is changed so that more persons are s

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Part I: If the criteria for determining what constitutes a
positive screening test is changed so
that more persons are screened as
positive for a disease, we would most likely say that:
The positive predictive value has increased in the
population.
The testing has become more specific.
There is a higher yield of negatives.
The prevalence of that disease has decreased in the
population.
The testing has become more sensitive.
Part II: In general, screening would be useful for diseases with
the following features:
Disease with a high prevalence in distinct segments of the
population
Diseases with a natural history that can be altered by medical
intervention
High prevalence disease for which there is no effective
intervention
Disease with a high secondary attack rate
A and B above
Part III:
Of 255 persons free of Crohn's disease, 230 tested
negative on the new screening test. What was the specificity?
90%
80%
10%
Cannot be calculated.
Part VI:
Positive and negative predictive values are influenced by the
prevalence of disease in the population that is being tested. If we
test in a high prevalence setting, it is more likely that persons
who test positive truly have disease than if the test is performed
in a population with low prevalence.
True
False
A medical center studied 1000 women with a palpable breast
mass. All of the women underwent biopsy (gold standard diagnostic
procedure) and mammography procedures. Of 600 women who had a
biopsy positive for cancer, 510 also had a positive
mammogram. A total of 400 women had a negative biopsy. Of
these 400 women, 20 had a positive mammogram. (Creating a 2 x 2
table might be a good idea here.)
After analyzing the study you conclude that the sensitivity of
the mammography is:
90/600 or 15%
380/470 or 80%
380/400 or 95%
510/530 or 96%
510/600 or 85%