Reference no: EM133476935
1. In your own words, define each of the following:
Sensitivity:
Specificity:
Positive Predictive Value:
Negative Predictive Value:
2. Cervical cancer is more common (higher prevalence) among Black women than white women. Using the same Papsmear screening test (sensitivity and specificity 97% and 98% respectively), which of the following would you expect?
a. The positive predictive value of the Pap smear screening test is higher in white women than Black women
b. The positive predictive value of the Pap smear screening test is higher in Black women than white women
c. The positive predictive value of the Pap smear screening test is the same in white and Black women
d. The positive predictive value of the Pap smear screening test is unrelated to the underlying prevalence
3. Early detection of breast cancer significantly improves prognosis (i.e. survival). Mammography is the "gold standard" clinical screening tool for breast cancer; however, breast self-exam may also be an effective early detection technique. To assess the validity of a breast self-exam (a screening test), a sample 3,625 of women were asked to complete a self-exam and undergo mammography (gold standard). The results of the self-exam were checked against those of the mammogram. A positive mammogram can be considered a true case of breast cancer for the purposes of this exercise. The results were as follows:
Mammography
Breast self-exam Positive Negative
Positive 122 57
Negative 25 3,421
a. The specificity of the breast self-exam was:
b. The sensitivity of the breast self-exam was:
c. The number of false positive breast self-exams was:
d. The number of false negative breast self-exams was:
e. The positive predictive value was:
f. The negative predictive value was:
Use the following information to answer questions 4-6:
The PHQ-9 is used widely in health studies as a screening tool for depression. Scores range from 0-27, with a higher score indicating more severe depressive symptoms. A cut-off of 10 has an 88% sensitivity and 88% specificity for depression diagnosis, when compared to psychiatrist diagnosis (the "Gold Standard.") Suppose the true prevalence of depression is 5% in your study population of 500 people.
4. Provide a correct interpretation of the 88% specificity of the PHQ-9?
5. If you chose to use a cutoff score of 15 instead of 10, circle what would happen to your sensitivity and specificity and provide an explanation?
Sensitivity: Increases Decreases
Specificity: Increases Decreases
Explanation:
6. Your colleague is considering using the PHQ-9 for research purposes and asks you what proportion of those who screen positive with the PHQ-9 will have depression. Which measure of screening validity should you respond with?
a. Positive predictive value
b. False negative %
c. False positive %
d. Sensitivity
e. Negative predictive value
Use the following information to answer questions 7-13:
You are conducting a study looking at the relationship between consuming soy milk and breast cancer. You hypothesize that those who drink soy milk have a lower odds of breast cancer. You recruit a sample of 1000 people (500 who drink soy milk, 500 who do not drink soy milk). You want to follow this sample for 10 years and screen them for breast cancer once per year. Before you start your study, you must decide on which cancer screening test you'll be using with your participants. You determine that it's most important for your test to correctly classify non-cases.
7. Which of the following did you determine to maximizing in the test you'll be using?
a. Sensitivity
b. Specificity
8. There are three new tests on the market. Using the following data, calculate the value of your answer above for all three tests AND indicate which test you should use in your study.
Gold Standard
New test # 1 Cancer No Cancer
Positive 150 25
Negative 10 65
Gold Standard
New test # 2 Cancer No Cancer
Positive 110 30
Negative 50 60
Gold Standard
New test # 3 Cancer No Cancer
Positive 155 20
Negative 5 70
9. Your colleagues are concerned that the sensitivity/specificity of the test might not be enough to decide on which test to use in your study. They ask you to calculate the positive and negative predicative value of the test you selected in the previous question.
10. Write an interpretation for the negative predictive value you noted in the previous question.
11. You are reviewing data from the first 5 years of your study. Answer the questions below using the data provided in the table is the appropriate measure of association to calculate for this data. Please explain your answer.
Cancer No Cancer Total
Drinks soy milk 2 498 500
Does not drink soy milk 5 495 500
Total 7 993 1000
a. What is the most appropriate measure of association to calculate here? Explain your answer.
b. Calculate the most appropriate measure of association.
c. Interpret the risk ratio of breast cancer among this sample.
12. Another researcher wants to repeat your study among a sample of people at high risk for breast cancer. This high risk sample of people will therefore have more cases of the disease. Circle what would happen to the sensitivity and positive predictive value of your screening test and explain your answer.
Sensitivity: Increase Stays the same Decreases
Explanation:
Positive predictive value: Increases Stays the same Decreases
Explanation:
13. Given your knowledge of the study design, the results, and your understanding of causality in epidemiology, circle if the following Hill's criteria are met or not met and explain your answer.
a. Dose-response relationship: Met Not met
Explanation:
b. Temporal relationship: Met Not met
Explanation: