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Old 01-31-2014
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Default biostatistics question

it's NOT AN NBME so dont worry


A 55 year old man visits his primary care physician with a complaint of urinary frequency. Examination finds a 1cm nodule on his prostate gland. The physician orders a prostate specific antigen serum test. By common standards a PSY Level greater than, 4mg/ml is considered abnormal. Using this standard, this test has a sensitivity, of 80% and a specificity of 90%. A recent published epidemiological article found that in a cross sectional study, 10% of men of this age have prostate cancer. the result on the patient's PSA is 7mg/nl. What is your best estimate of the likelihood that this man actually has prostate cancer?


please help answer with explanation if you can thanks.
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Old 02-01-2014
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Default

Quote:
Originally Posted by obinocle View Post
it's NOT AN NBME so dont worry


A 55 year old man visits his primary care physician with a complaint of urinary frequency. Examination finds a 1cm nodule on his prostate gland. The physician orders a prostate specific antigen serum test. By common standards a PSY Level greater than, 4mg/ml is considered abnormal. Using this standard, this test has a sensitivity, of 80% and a specificity of 90%. A recent published epidemiological article found that in a cross sectional study, 10% of men of this age have prostate cancer. the result on the patient's PSA is 7mg/nl. What is your best estimate of the likelihood that this man actually has prostate cancer?


please help answer with explanation if you can thanks.


We are asked for ppv
Prevalence 10%

Take any number to be the total number of people and u would arrive at same answer. So say total number of pple 1000


By calculation Tp= 80, fp= 90
So ppv= 80/170= 47%

Kaplan vedio has exactly same question except that prev there is 20% and u hv interchanged the spec and sensitivity values
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