WBR0792
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| Author | [[PageAuthor::Serge Korjian M.D. (Reviewed by Serge Korjian)]] |
|---|---|
| Exam Type | USMLE Step 1 |
| Main Category | Biostatistics/Epidemiology |
| Sub Category | Dermatology |
| Prompt | [[Prompt::A company is testing a new diagnostic tool for the detection of squamous cell carcinoma of the skin and comparing the results to biopsy specimens validated by professional dermatopathologists. The results are shown below. What is the probability that a person really doesn't have squamous cell carcinoma if his test result comes back negative?
|
| Answer A | 82.75% |
| Answer A Explanation | This refers to the sensitivity. |
| Answer B | 80% |
| Answer B Explanation | This refers to the positive predictive value. |
| Answer C | 94.11% |
| Answer C Explanation | This refers to the NPV. |
| Answer D | 93.02% |
| Answer D Explanation | This refers to the specificity. |
| Answer E | 76.92% |
| Answer E Explanation | This does not refer to any particular value. |
| Right Answer | C |
| Explanation | [[Explanation::The prompt in this question refers to the negative predictive value of the test being studied. To test sensitivity, specificity, and negative and positive predictive values of a certain test, results need to be compared to the gold standard test for the detection of the disease or outcome in question. The negative predictive value is the probability that a person really doesn't have the disease given that his test result is negative. The calculation is shown below.
|
| Approved | Yes |
| Keyword | Negative predictive value, Positive predictive value |
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