WBR0791

Author	[[PageAuthor::Serge Korjian M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biostatistics/Epidemiology
Sub Category	SubCategory::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? ]]
Answer A	AnswerA::Sensitivity: 93.8%% / Specificity: 74.5%
Answer A Explanation	AnswerAExp::This is the correct combination.
Answer B	AnswerB::Sensitivity: 74.5% / Specificity: 93.8
Answer B Explanation	AnswerBExp::These values are incorrect.
Answer C	AnswerC::Sensitivity: 71.4% / Specificity: 94.6%
Answer C Explanation	AnswerCExp::These results refer to the positive predictive value (PPV) and the negative predictive value (NPV), respectively.
Answer D	AnswerD::Sensitivity: 94.6% / Specificity: 71.4%
Answer D Explanation	AnswerDExp::These values are incorrect.
Answer E	AnswerE::Cannot be calculated with the given data
Answer E Explanation	AnswerEExp::All the values needed are available to calculate both the sensitivity and specificity.
Right Answer	RightAnswer::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. Educational Objective: References: Chow S, Liu J. Design and Analysis of Clinical Trials, Concepts and Methodologies. John Wiley & Sons; 2013.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Specificity, WBRKeyword::Sensitivity
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::