WBR0792

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biostatistics/ Epidemiology
Sub Category	SubCategory::Dermatology
Prompt	[[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? ]]
Answer A	AnswerA::82.75%
Answer A Explanation	AnswerAExp::This refers to the sensitivity.
Answer B	AnswerB::80%
Answer B Explanation	AnswerBExp::This refers to the positive predictive value.
Answer C	AnswerC::94.11%
Answer C Explanation	AnswerCExp::This refers to the NPV.
Answer D	AnswerD::93.02%
Answer D Explanation	AnswerDExp::This refers to the specificity.
Answer E	AnswerE::76.92%
Answer E Explanation	AnswerEExp::This does not refer to any particular value.
Right Answer	RightAnswer::C
Explanation	[[Explanation::To test sensitivity and specificity of a certain test, results need to be compared to that of the gold standard for the detection of the studied disease or outcome. 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. Educational Objective: Negative predictive value (NPV) = [True negative/(True negative + False negative)] Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::Negative, WBRKeyword::predictive, WBRKeyword::value, WBRKeyword::negative predictive value
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::