A new stool test for H. pylori infection yields positive results in 80% of infected patients and in 10% of uninfected patients.  Prevalence of H. pylori infection in the population is 10%.  What is the probability that a patient who tests positive with the new test is infected with H. pylori?

A 52-year-old Caucasian female presents to your office with a self-palpated thyroid nodule.  After the appropriate work-up, fine-needle aspiration (FNA) of the nodule is performed.  The FNA result is negative.  As you are explaining the test result, the patient asks, “What are the chances that I really do not have cancer?”  You reply that the probability of thyroid cancer is low in her case because FNA has a high:

A serologic test is introduced for the diagnosis of hepatitis C virus (HCV) infection.  When tested on the general population, the sensitivity and specificity of the test are 85% and 78%, respectively.  If the test is applied to a population of IV drug abusers with a higher probability of HCV infection, which of the following changes would you expect?

A new test for early detection of ovarian cancer is under investigation.  It measures a serum marker level as an indicator of the neoplastic process.  The results of the study demonstrate that the serum marker level is correlated with the presence of ovarian cancer in the women under study.

If the cutoff point is moved from X to A, the positive predictive value will:

190 patients with exercise-induced chest pain and a normal baseline ECG undergo stress ECG followed by coronary angiography.  Coronary angiography is interpreted as positive if at least one of coronary arteries has an atherosclerotic lesion with ≥70% luminal stenosis.  The following results are obtained (see the table below).

According to the study results, if a patient with exercise-induced chest pain has a negative ECG stress test, what is his/her probability of having a positive result on coronary angiography?

Several tests have been developed to measure serologic markers of breast cancer.  The sensitivity and specificity for diagnosis of early stage breast cancer vary from test to test.  If positive, which of the following tests will have the highest predictive value for the disease?