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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 01-31-2014
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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.
lets take population of 1000 people
prevalence of disease (10%)=100 people
sensitivity=80% from this 100 diseased people or 80 is true positive+remaining 20 is false negative
specificity=90% from the remaining 900 healthy people or 810 is true negative and 90 is false positive


now we should find the positive predictive value = TP/TP+FP=80/80+90=47%

thats my assumption
whats the correct answer ?
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Old 01-31-2014
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thank you thank you thank you thank you !!!! muah muah muah!!
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