Epidemiology & Screening

Topics in this chapter

• Disease Frequency Measures
• Measures of Association
• Observational Study Designs
• Experimental Study Designs
• Bias and Confounding
• Screening Test Evaluation

Practice questions

1. Question 1Q-796B60

   A new diagnostic test for typhoid fever is evaluated against blood culture (gold standard). Out of 200 confirmed typhoid patients, 160 test positive. Out of 300 non-typhoid patients, 60 test positive. What is the sensitivity and specificity of the test, respectively?

   1. A.80% and 80%
   2. B.80% and 60%
   3. C.60% and 80%
   4. D.90% and 70%
   See the answer and solution
2. Question 2Q-0FD324

   During an outbreak of cholera in a village of 5,000 population, 250 cases are reported over a period of two weeks, out of which 25 patients die. What is the case fatality rate (CFR) of cholera in this outbreak?

   1. A.0.5%
   2. B.5.0%
   3. C.10.0%
   4. D.25.0%
   See the answer and solution
3. Question 3Q-109A20

   In a cohort study investigating the association between smoking and lung cancer, 50 out of 1,000 smokers develop lung cancer, while 5 out of 1,000 non-smokers develop lung cancer. What is the relative risk?

   1. A.2.5
   2. B.5.0
   3. C.10.0
   4. D.50.0
   See the answer and solution
4. Question 4Q-1F9865

   A screening test for diabetes has high sensitivity but low specificity. Which of the following is the most appropriate implication of using this test in a community?

   1. A.It will miss a large number of true diabetic patients.
   2. B.It will lead to a high number of false positives requiring confirmatory tests.
   3. C.It will have a very high positive predictive value.
   4. D.It is best used as a confirmatory test rather than a screening test.
   See the answer and solution
5. Question 5Q-8DF157

   If the prevalence of a disease in a population increases, what happens to the Positive Predictive Value (PPV) of a screening test with constant sensitivity and specificity?

   1. A.PPV increases
   2. B.PPV decreases
   3. C.PPV remains unchanged
   4. D.PPV becomes equal to specificity
   See the answer and solution