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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor= {{SSK}} (Reviewed by Serge Korjian)
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Cardiology
|SubCategory=Reproductive
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Cardiology
|SubCategory=Reproductive
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Cardiology
|SubCategory=Reproductive
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Cardiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|SubCategory=Reproductive
|SubCategory=Cardiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|SubCategory=Reproductive
|SubCategory=Cardiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|SubCategory=Reproductive
|SubCategory=Cardiology
|MainCategory=Biostatistics/Epidemiology
|MainCategory=Biostatistics/ Epidemiology
|SubCategory=Reproductive
|MainCategory=Biostatistics/ Epidemiology
|MainCategory=Biostatistics/Epidemiology
|SubCategory=Cardiology
|MainCategory=Biostatistics/Epidemiology
|Prompt=A company is testing a new diagnostic tool for the detection of squamous cell carcinoma of the skin and comparing the results to biopsy specimens validated by professional dermatopathologists. The results are shown below. What is the probability that a person really doesn't have squamous cell carcinoma if his test result comes back negative?
|SubCategory=Reproductive
|Prompt=A new urine pregnancy test is being evaluated before marketing. A trial is conducted to compare the results of this new test to a combination of imaging and blood human chorionic gonadotropin (HCG) levels to validate the pregnancy. A table comparing the results of the study is shown below. What is the probability that a woman is truly pregnant if her urine pregnancy test is positive?




[[Image:WBR0792.jpg|500px]]
[[Image:WBR0793.jpg|500px]]
|Explanation=The negative predictive value is the probability that a person really doesn't have disease if a test result is negative. The calculation is shown below.
|Explanation=The positive predictive value is the probability that a person really has a condition if their test result is positive. The calculation is shown below.
 


[[Image:Biostat.png|600px]]
[[Image:Biostat.png|600px]]
|AnswerA=82.75%
|AnswerA=85.71%
|AnswerAExp=This refers to the sensitivity.
|AnswerAExp=This refers to the sensitivity.
|AnswerB=80%
|AnswerB=75%
|AnswerBExp=This refers to the positive predictive value.
|AnswerBExp=This refers to the positive predictive value.
|AnswerC=94.11%
|AnswerC=89.28%
|AnswerCExp=This refers to the NPV.
|AnswerCExp=This refers to the NPV.
|AnswerD=93.02%
|AnswerD=80.64%
|AnswerDExp=This refers to the specificity.
|AnswerDExp=This refers to the specificity.
|AnswerE=76.92%
|AnswerE=62%
|RightAnswer=C
|AnswerEExp=This does not refer to any particular value.
|WBRKeyword=Negative predictive value
|EducationalObjectives=The positive predictive value (PPV) is the probability that a person really has a condition if their test result is positive. ''PPV = [True positive/(True positive+False positive)]''
|Approved=No
|References=Chow S, Liu J. Design and Analysis of Clinical Trials, Concepts and Methodologies. John Wiley & Sons; 2013.
|RightAnswer=B
|WBRKeyword=Positive predictive value
|Approved=Yes
}}
}}

Latest revision as of 01:43, 28 October 2020
Author [[PageAuthor::Serge Korjian M.D. (Reviewed by Serge Korjian)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Biostatistics/Epidemiology
Sub Category SubCategory::Reproductive
Prompt [[Prompt::A new urine pregnancy test is being evaluated before marketing. A trial is conducted to compare the results of this new test to a combination of imaging and blood human chorionic gonadotropin (HCG) levels to validate the pregnancy. A table comparing the results of the study is shown below. What is the probability that a woman is truly pregnant if her urine pregnancy test is positive?


]]

Answer A AnswerA::85.71%
Answer A Explanation AnswerAExp::This refers to the sensitivity.
Answer B AnswerB::75%
Answer B Explanation AnswerBExp::This refers to the positive predictive value.
Answer C AnswerC::89.28%
Answer C Explanation AnswerCExp::This refers to the NPV.
Answer D AnswerD::80.64%
Answer D Explanation AnswerDExp::This refers to the specificity.
Answer E AnswerE::62%
Answer E Explanation AnswerEExp::This does not refer to any particular value.
Right Answer RightAnswer::B
Explanation [[Explanation::The positive predictive value is the probability that a person really has a condition if their test result is positive. The calculation is shown below.


Educational Objective: The positive predictive value (PPV) is the probability that a person really has a condition if their test result is positive. PPV = [True positive/(True positive+False positive)]
References: Chow S, Liu J. Design and Analysis of Clinical Trials, Concepts and Methodologies. John Wiley & Sons; 2013.]]

Approved Approved::Yes
Keyword WBRKeyword::Positive predictive value
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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