Can anyone help me with this question? It\'s to study for the final. A recent na
ID: 3154191 • Letter: C
Question
Can anyone help me with this question? It's to study for the final. A recent nationwide study investigated the value of the prostate-specific antigen (PSA) blood test for the detection of prostate cancer among 100,000 men 50 years of age and older. Of the 686 men who tested positive on the PSA test, a total of 281 were ultimately diagnosed with prostate cancer, either by immediate needle biopsy or during 12 months of watchful waiting. An additional 45 men who tested negative on the PSA test were ultimately diagnosed with prostate cancer during 12 months of follow-up.
1) Set up the 2X2 contingency table for the data.
2) What is the sensitivity of the PSA test? Interpret the result.
3) What is the specificity of the PSA test? Interpret the result.
4) What is the positive predictive value (PPV) of the PSA test? Interpret the result. 5) What is the negative predictive value (NPV) of the PSA test? Interpret the result.
Explanation / Answer
Can anyone help me with this question? It's to study for the final. A recent nationwide study investigated the value of the prostate-specific antigen (PSA) blood test for the detection of prostate cancer among 100,000 men 50 years of age and older. Of the 686 men who tested positive on the PSA test, a total of 281 were ultimately diagnosed with prostate cancer, either by immediate needle biopsy or during 12 months of watchful waiting. An additional 45 men who tested negative on the PSA test were ultimately diagnosed with prostate cancer during 12 months of follow-up.
Test +
Test -
Total
Disease+
281
45
326
Disease -
405
99269
99674
Total
686
99314
100000
2) What is the sensitivity of the PSA test? Interpret the result.
Sensitivity =281/326 =0.862
The fraction of those with the disease correctly identified as positive by the test.
specificity = 99269/99674 = 0.99594
The fraction of those without the disease correctly identified as negative by the test
4) What is the positive predictive value (PPV) of the PSA test? Interpret the result.
PPV = 281/686 =0.4096
The fraction of people with positive tests who actually have the condition.
5) What is the negative predictive value (NPV) of the PSA test? Interpret the result.
NPV =99269/ 99314 =0.99955
The fraction of people with negative tests who actually don't have the condition.
Test +
Test -
Total
Disease+
281
45
326
Disease -
405
99269
99674
Total
686
99314
100000
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