WBR0741

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biostatistics/Epidemiology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A cardiologist interpreting echocardiograms notes systematically his observations before he reads the clinical presentation and the history of the patient from his chart. After documenting his findings, he retrieves the patient's charts and compares his findings to the patient's clinical data. When asked by his students, the cardiologist replies that this technique is designed by healthcare systems to prevent bias. Which type of bias is this technique most likely reducing?]]
Answer A	AnswerA::Procedure bias
Answer A Explanation	AnswerAExp::Procedure bias is when subjects of two arms in a study experience a different course during the study or are treated differently.
Answer B	AnswerB::Lead-time bias
Answer B Explanation	AnswerBExp::Lead-time bias is when early detection is misinterpreted as increased survival.
Answer C	AnswerC::Recall bias
Answer C Explanation	AnswerCExp::Recall bias is when a person experiencing the disease might know more of the disease than subjects who do not know of the presence of the disease.
Answer D	AnswerD::Selection bias
Answer D Explanation	AnswerDExp::Selection bias is when subjects are selected in a non-random fashion.
Answer E	AnswerE::Observer bias
Answer E Explanation	AnswerEExp::Observer bias is when the researcher is aware beforehand of what to expect and is unconsciously influenced by his knowledge.
Right Answer	RightAnswer::E
Explanation	[[Explanation::Using the blinded technique, the cardiologist is reducing observer bias. The latter is defined as pre-existing knowledge among the physician/researcher that unconsciously alters the study's outcome. Observer bias is also seen in clinical trials when an investigator knows beforehand which group of subjects is receiving which medication; this knowledge might unconsciously affect the investigator's findings. Educational Objective: Blind experimentation reduces observer bias. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::observer, WBRKeyword::bias, WBRKeyword::blind, WBRKeyword::experiment, WBRKeyword::technique, WBRKeyword::cardiologist, WBRKeyword::echocardiogram
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