WBR0418

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Alison Leibowitz)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biostatistics/Epidemiology
Sub Category	SubCategory::Vascular
Prompt	[[Prompt::The following table displays the results of a study investigating a new test for diagnosing aortic stiffness. What are the approximate sensitivity and specificity of the new test? ]]
Answer A	[[AnswerA::Sensitivity = 83% Specificity = 67%]]
Answer A Explanation	[[AnswerAExp::Sensitivity (%) = TP/ (TP+FN) x 100 = 83% Specificity (%) = TN/ (TN + FP) x 100 = 67%]]
Answer B	[[AnswerB::Sensitivity = 83% Specificity = 80%]]
Answer B Explanation	AnswerBExp::Sensitivity is correct. However, 80% represents the negative predictive value (NPV) of the test. NPV is calculated using the following equation: NPV = TN/ (TN+FN)
Answer C	[[AnswerC::Sensitivity = 71% Specificity = 80%]]
Answer C Explanation	[[AnswerCExp::71% represents the positive predictive value (PPV) of the test. PPV is calculated using the following equation: PPV = TP/ (TP+FP). 80% represents the negative predictive value (NPV) of the test. NPV is calculated using the following equation: NPV = TN/ (TN+FN)]]
Answer D	[[AnswerD::Sensitivity = 80% Specificity = 71%]]
Answer D Explanation	[[AnswerDExp::71% represents the positive predictive value (PPV) of the test. PPV is calculated using the following equation: PPV = TP/ (TP+FP). 80% represents the negative predictive value (NPV) of the test. NPV is calculated using the following equation: NPV = TN/ (TN+FN)]]
Answer E	[[AnswerE::Sensitivity = 71% Specificity = 67%]]
Answer E Explanation	AnswerEExp::71% represents the positive predictive value (PPV) of the test. PPV is calculated using the following equation: PPV = TP/ (TP+FP). On the other hand, specificity is correct.
Right Answer	RightAnswer::A
Explanation	[[Explanation::Sensitivity (%) = TP/ (TP+FN) x 100 = 100/(100+20) x 100 = (100/120) x 100= 83% Specificity (%) = TN/ (TN + FP) x 100 = 80/(80+40) x 100 = (80/120) x 100 = 67% Educational Objective: Sensitivity (%) = TP/ (TP+FN) x 100 Specificity (%)= TN/ (TN + FP) x 100 References: First Aid 2014 page 51]]
Approved	Approved::Yes
Keyword	WBRKeyword::Specificity, WBRKeyword::Sensitivity, WBRKeyword::Calculation, WBRKeyword::Equation, WBRKeyword::Aortic stiffness
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::