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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor= {{YD}}  {{Alison}}
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Vascular
|SubCategory=Vascular
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Vascular
|SubCategory=Vascular
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Vascular
|SubCategory=Vascular
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Vascular
|SubCategory=Vascular
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Vascular
|SubCategory=Vascular
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Vascular
|SubCategory=Vascular
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Vascular
|SubCategory=Vascular
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Vascular
|SubCategory=Vascular
|Prompt=A study is interested in investigating a new test in diagnosing aortic stiffness. The following table shows the results of the study.  What are the approximate sensitivity and specificity of the new test?
|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?


[[Image:WBR Aortic Stiffness biostatistics.png]]
[[Image:WBR Aortic Stiffness biostatistics.png|350px]]
|Explanation=Sensitivity (%) = TP/ (TP+FN) x 100 = 100/(100+20) x  100 = (100/120) x 100= 83%
|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%
Specificity (%) = TN/ (TN + FP) x 100 = 80/(80+40) x 100 = (80/120) x 100 = 67%


[[Image:WBR Aortic Stiffness biostatistics explanation.png]]
[[Image:WBR Aortic Stiffness biostatistics explanation.png|350px]]
|AnswerA=Sensitivity = 83%
|AnswerA=Sensitivity = 83%
Specificity = 67%
Specificity = 67%
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Specificity (%) = TN/ (TN + FP) x 100 = 67%
Specificity (%) = TN/ (TN + FP) x 100 = 67%
|AnswerB=Sensitivity = 83%
|AnswerB=Sensitivity = 83%
Specificity = 80%
|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)
|AnswerC=Sensitivity = 71%
Specificity = 80%
|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)
|AnswerD=Sensitivity = 80%
Specificity = 71%
Specificity = 71%
|AnswerBExp=71% corresponds to the positive predictive value (PPV). PPV is calculated by the following equation: PPV = TP/ (TP+FP)
|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)
|AnswerC=Sensitivity = 83%
|AnswerE=Sensitivity = 71%
Specificity = 83%
|AnswerCExp=Both values correspond to sensitivity.
|AnswerD=Sensitivity = 67%
Specificity = 83%
|AnswerDExp=The inverse is true.
|AnswerE=Sensitivity = 67%
Specificity = 67%
Specificity = 67%
|AnswerEExp=Both values correspond to specificity.
|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.
|EducationalObjectives=Sensitivity (%) = TP/ (TP+FN) x 100
Specificity (%)= TN/ (TN + FP) x 100
|References=First Aid 2014 page 51
|RightAnswer=A
|RightAnswer=A
|Approved=No
|WBRKeyword=Specificity, Sensitivity, Calculation, Equation, Aortic stiffness
|Approved=Yes
}}
}}

Latest revision as of 00:29, 28 October 2020
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::
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