WBR0793

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 his 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 his 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::