Exercise 5: (1 point) You are a physician. You received the results of your 45 y

Question

Exercise 5: (1 point) You are a physician. You received the results of your 45 year old patient's mammogram. The study is interpreted as "suspicious for malignancy" by your radiologist. Your patient asks you: "Does this mean I have cancer?", and you (comectly) answer "No, we have to do further testing Your patient then asks, "OK, I understand that the mammogram isn't the final answer, but given what we know now, what are the chances that I have breast cancer?" Assume that the overall risk of breast cancer in any 45 year old woman, regardless of mammmogram result, is 0.1% orone in a thousand. Assume also that mammography is 80% sensitive (80% of individuals with breast cancer have an abnormal mammogram) and 95% specific (95% individuals without breast cancer have a nomal mammogram). If we consider a population of 10,000 wome, answer the following questions:

Explanation / Answer

a) Number of women with cancer = 10

b) Number of women without cancer = 10,000-10 = 9990

c) Number of women with cancer with 80% sensitive test = 10x0.8 = 8

d) Number of women without cancer with a 95% specific test = 0.95x9990 = 9490

e)

f) Positive predictive value = 8x100/508 = 1.575%

Beast Cancer is present No breast cancer Total Positive mammogram 0.80x10 = 8 9990 - 9490 = 500 508 Negative mammogram 10 - 8 = 2 0.95x9990 = 9490 9492 Total 10000x0.001 = 10 10000-10 = 9990 10,000

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