WBR0791: Difference between revisions

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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{SSK}}
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/Epidemiology
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|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Cardiology
|SubCategory=Cardiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/Epidemiology
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|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Cardiology
|SubCategory=Cardiology
|Prompt=A new diagnostic test is being evaluated for the diagnosis of 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. Knowing that the gold standard has a sensitivity and specificity approaching 100% it is used to determine the true incidence of DVT.  The table below shows the result of the initial data collection. Which of the following combinations are true regarding this diagnostic test?
|Prompt=A new diagnostic test is being evaluated for the diagnosis of 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. Knowing that the gold standard has a sensitivity and specificity approaching 100%, it is used to determine the true incidence of DVT.  The table below shows the result of the initial data collection. Which of the following combinations are true regarding this diagnostic test?




[[Image:WBR0791.jpg|500px]]
[[Image:WBR0791.jpg|500px]]
|Explanation=[[Image:Biostat.png|600px]]
|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 below.
 
 
[[Image:Biostat.png|600px]]
|AnswerA=Sensitivity: 93.75 / Specificity: 74.46
|AnswerA=Sensitivity: 93.75 / Specificity: 74.46
|AnswerAExp=This is the correct combination.
|AnswerAExp=This is the correct combination.
|AnswerB=Sensitivity: 74.46 / Specificity: 93.75
|AnswerB=Sensitivity: 74.46 / Specificity: 93.75
|AnswerBExp=Incorrect
|AnswerBExp=These values are incorrect.
|AnswerC=Sensitivity: 71.42 / Specificity: 94.59
|AnswerC=Sensitivity: 71.42 / Specificity: 94.59
|AnswerCExp=This refers to the positive predictive value and the negative predictive value respectively.
|AnswerCExp=This refers to the positive predictive value and the negative predictive value respectively.
|AnswerD=Sensitivity: 94.59 / Specificity: 71.42
|AnswerD=Sensitivity: 94.59 / Specificity: 71.42
|AnswerDExp=Incorrect
|AnswerDExp=These values are incorrect.
|AnswerE=Cannot be calculated with the given data
|AnswerE=Cannot be calculated with the given data
|AnswerEExp=All the values needed are available to calculate both the sensitivity and specificity.
|AnswerEExp=All the values needed are available to calculate both the sensitivity and specificity.
|EducationalObjectives=[[Image:Biostat.png|600px]]
|References=Chow S, Liu J. Design and Analysis of Clinical Trials, Concepts and Methodologies. John Wiley & Sons; 2013.
|RightAnswer=A
|RightAnswer=A
|WBRKeyword=Specificity, Sensitivity
|WBRKeyword=Specificity, Sensitivity
|Approved=No
|Approved=No
}}
}}

Revision as of 15:54, 18 September 2014

 
Author [[PageAuthor::Serge Korjian M.D.]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Biostatistics/Epidemiology
Sub Category SubCategory::Cardiology
Prompt [[Prompt::A new diagnostic test is being evaluated for the diagnosis of 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. Knowing that the gold standard has a sensitivity and specificity approaching 100%, it is used to determine the true incidence of DVT. The table below shows the result of the initial data collection. Which of the following combinations are true regarding this diagnostic test?


]]

Answer A AnswerA::Sensitivity: 93.75 / Specificity: 74.46
Answer A Explanation AnswerAExp::This is the correct combination.
Answer B AnswerB::Sensitivity: 74.46 / Specificity: 93.75
Answer B Explanation AnswerBExp::These values are incorrect.
Answer C AnswerC::Sensitivity: 71.42 / Specificity: 94.59
Answer C Explanation AnswerCExp::This refers to the positive predictive value and the negative predictive value respectively.
Answer D AnswerD::Sensitivity: 94.59 / Specificity: 71.42
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 below.



Educational Objective:
References: Chow S, Liu J. Design and Analysis of Clinical Trials, Concepts and Methodologies. John Wiley & Sons; 2013.]]

Approved Approved::No
Keyword WBRKeyword::Specificity, WBRKeyword::Sensitivity
Linked Question Linked::
Order in Linked Questions LinkedOrder::