Exercise 3.3 A rapid screening test for women with HPV (human papillomavirus) is
ID: 3202114 • Letter: E
Question
Exercise 3.3
A rapid screening test for women with HPV (human papillomavirus) is being evaluated for its effectiveness and sensitivity as a screening test in college healthcare clinics. In order to determine the effectiveness of the HPV test, it was administered to 2,000 female college students. Tests were confirmed by comparisons to the gold standard test (Pap smears). Prevalence of HPV was 12% in the female college population; 352 students tested positive for HPV. The HPV test was found to be 92% specific. Create a 2 x 2 table that accurately describes this test and use this information to answer the following questions.
HPV
No HPV
Total
+ Test
Test
Totals
What is the sensitivity of this test?
What is the positive predictive value of this test?
What is the negative predictive value of this test?
If everything else remained the same, what would happen to the predictive value of a positive test if the disease prevalence increased in the population?
How many false negatives are there with this test?
How many false positives are there with this test?
Explain how false positives and false negatives can affect your patient population.
If the gold standard test (Pap smear) has a sensitivity of 94% and a specificity of 88%, which test (the new HPV test or Pap test) would you prefer to use in your healthcare clinic if you want to reduce the number of false-negative test results in your clinic? Which test would you prefer if you want to reduce the number of false-positive test results? Explain your answer using the results from previous calculations.
Exercise 3.4
AS investigators samples a groups of clients from a clinic based on their disease status---in particular, whether or not they have HTN. Of the 250 people sampled, 40% were found to have HTN. Knowing their disease status, a questionnaire is administered to the people in the study to determine how many have a family history (FHx) of stroke (in a first-degree relative). Of the people without HTN, 8% had a FHx of stroke. Of the the people with HTN, 37% had a FHX of stroke. Create a 2 x 2 table using this information and answers the following questions.
HTN
No HTN
Totals
+ FHx stroke
FHx stroke
Totals
What type of study design is this?
Can you calculate RR (relative risk using the data? Why or why not)
Can you calculate OR (odds ratio) using the data?
Calculate the correct descriptive statistics for this study (either RR or OR)
What is the correct interpretation of the statistic used?
Patients with a FHx of stroke are 6.75 times more likely to develop HTN than patients with no FHx of stroke.
Patients with HTN are 6.75 times more likely to have a FHx of stroke than those with normal blood pressure.
What are possible errors that could be made in this type of study?
HPV
No HPV
Total
+ Test
Test
Totals
Explanation / Answer
Exercise 3.3:
Following is the false matrix:
MS Excel formula:
What is the sensitivity of this test?
12%
What is the positive predictive value of this test?
352
What is the negative predictive value of this test?
1648
If everything else remained the same, what would happen to the predictive value of a positive test if the disease prevalence increased in the population?
Ans: In this case, the positive predicted value will also increase proportionately
How many false negatives are there with this test?
29
How many false positives are there with this test?
141
Explain how false positives and false negatives can affect your patient population.
Ans: The accuracy, FPR, TPR will get affected.
Q: If the gold standard test (Pap smear) has a sensitivity of 94% and a specificity of 88%, which test (the new HPV test or Pap test) would you prefer to use in your healthcare clinic if you want to reduce the number of false-negative test results in your clinic? Which test would you prefer if you want to reduce the number of false-positive test results?
Ans. the gold standard test (Pap smear) will be preferred since it has more sensitivity of 94% means less False negative result.
Actual HPV No HPV Totals Predicted + Test 211 141 352 Test 29 1619 1648 Total 240 1760 2000 12% 92% Sensitivity SpecificityRelated Questions
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