WBR0791
| Author | [[PageAuthor::Serge Korjian M.D. (Reviewed by Yazan Daaboul, M.D.)]] |
|---|---|
| Exam Type | USMLE Step 1 |
| Main Category | Biostatistics/Epidemiology |
| Sub Category | Vascular |
| Prompt | [[Prompt::A new diagnostic test is being evaluated for the diagnosis of deep venous thrombosis (DVT). Patients presenting to a large central hospital with symptoms suggestive of DVT are evaluated using this new test in conjunction with the gold standard for diagnosis. Assuming that the gold standard has a sensitivity and specificity approaching 100%, it is used to determine the true incidence of DVT. The table below demonstrates the result of the initial data collection. Which of the following combinations is true regarding this diagnostic test?
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| Answer A | Sensitivity: 93.8%% / Specificity: 74.5% |
| Answer A Explanation | This is the correct combination. |
| Answer B | Sensitivity: 74.5% / Specificity: 93.8 |
| Answer B Explanation | These values are incorrect. |
| Answer C | Sensitivity: 71.4% / Specificity: 94.6% |
| Answer C Explanation | These results refer to the positive predictive value (PPV) and the negative predictive value (NPV), respectively. |
| Answer D | Sensitivity: 94.6% / Specificity: 71.4% |
| Answer D Explanation | These values are incorrect. |
| Answer E | Cannot be calculated with the given data |
| Answer E Explanation | All the values needed are available to calculate both the sensitivity and specificity. |
| Right Answer | A |
| Explanation | [[Explanation::
Sensitivity and specificity are measures of the performance of a classification test (positive or negative). Sensitivity answers the following question: if a person has a disease, how often will the test be positive?. Tests that are highly sensitive help rule out a disease when they are negative. Highly sensitive tests are usually used for screening. On the other hand, specificity answers the following question:if a person does not have the disease how often will the test be negative?. Tests that are highly specific help rule in a disease when they are positive. Highly specific tests are usually used to confirm a diagnosis after patients have been screened. Sensitivity and specificity can be calculated using the formulas provided. |
| Approved | Yes |
| Keyword | Specificity, Sensitivity |
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