WBR0391

Author	[[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biostatistics/Epidemiology
Sub Category	SubCategory::Renal
Prompt	[[Prompt::A case-control study investigating the association between the current use of non-steroidal anti-inflammatory drugs (NSAIDs), for more than 1 year, and impaired renal function. 2000 males and females over the age of 50 are surveyed and the results of the study have been categorized in the following table. Which of the following numbers represents the odds ratio for renal impairment among patients with a history of NSAID use, versus those without a history of NSAID use? ]]
Answer A	AnswerA::0.041
Answer A Explanation	[[AnswerAExp::0.041 represents the attributable risk, calculated using the following equation: Attributable Risk = (a/[a+b]) – (c/[c+d])]]
Answer B	AnswerB::0.500
Answer B Explanation	AnswerBExp::0.500 does not correspond to any relevant value.
Answer C	AnswerC::1.066
Answer C Explanation	[[AnswerCExp::1.066 represents the relative risk (RR), often used in cohort studies, calculated with the following equation: RR = (a/[a+b]) / (c/[c+d])]]
Answer D	AnswerD::1.200
Answer D Explanation	AnswerDExp::1.200 correctly corresponds to the odds ratio.
Answer E	AnswerE::1.500
Answer E Explanation	AnswerEExp::1.500 does not correspond to any relevant value.
Right Answer	RightAnswer::D
Explanation	[[Explanation:: The odds ratio (OR) in this scenario is calculated using the equation: OR = ad/bc = (800 x 300)/(400 x 500) = 240000/200000 = 1.2 Educational Objective: The odds ratio is calculated using the equation: OR = ad/bc References: First Aid 2014 page 50]]
Approved	Approved::Yes
Keyword	WBRKeyword::odds ratio, WBRKeyword::OR, WBRKeyword::formulas, WBRKeyword::formula, WBRKeyword::case-control, WBRKeyword::equation
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::