SCREENING FOR DISEASESAssignment OverviewInfection with the human immunodeficiency virus (HIV) is routinely diagnosed by detecting the presence of specific antibodies in the patient?s serum. Although the presence of the virus itself can be now be detected (i.e. polymerase chain reaction [PCR] to measure plasma HIV RNA, or ?viral load?), these tests remain expensive and require laboratory techniques that are not routinely available. The diagnosis of HIV infection begins with an enzyme immunoassay (EIA). The optical density (OD) of the patient?s EIA is compared to a control specimen (OD ratio). If the OD ratio is ? above the established cutoff for that control sample on repeat testing the specimen is termed ?repeatedly reactive?. The EIA is relatively sensitive, fast, simple and inexpensive which makes it an appropriate screening test. However, if one examines the ODs for a large group of samples from patients with and without true HIV infection you can see that there is some overlap in their EIA results if a value of A is used for the cutoff:Hypothetical distribution of OD ratios for patients with and without HIV infection.Hypothetical distribution of OD ratios for patients with and without HIV infection.Patients with HIV infection are depicted with blue, thick line,those without HlV with red, thin line.Where a cutoff is drawn to determine a diagnostic test result may be somewhat arbitrary.Case AssignmentAnswer these questions:1. What would be the impact on this test?s sensitivity if you moved the cutoff for a positive result from A to B? What about specificity? What would happen to sensitivity and specificity if you moved the cutoff from A to C? Where would you put the cutoff for this test? What is the relationship between sensitivity and specificity for any given test?2. Where would the director of the Blood Bank who is screening donated blood for HIV antibody want to put the cutoff? What would be the potential problem caused by this decision? Where would an investigator enrolling high-risk patients in a clinical trial for an experimental, potentially toxic antiretroviral draw the cutoff? What would be the potential problem caused by this decision? In your answer please detail possible ethical and legal issues of possible concern.Assignment ExpectationsLength: Case assignments should be at least 2 pages (500 words) in length.References: At least two references must be included from academic sources (e.g. peer-reviewed journal articles). Required readings are included. Quoted material should not exceed 10% of the total paper (since the focus of these assignments is critical thinking). Use your own words and build on the ideas of others. When material is copied verbatim from external sources, it MUST be enclosed in quotes. The references should be cited within the text and also listed at the end of the assignment in the References section (APA format recommended).Organization: Subheadings should be used to organize your paper according to questionFormat: APA format is recommended for this assignment. See Syllabus page for more information on APA format.Grammar and Spelling: While no points are deducted, assignments are expected to adhere to standards guidelines of grammar, spelling, punctuation, and sentence syntax. Points may be deducted if grammar and spelling impact clarity.The following items will be assessed in particular:? Achievement of learning objectives for case assignment? Relevance (e.g. all content is connected to the question)? Precision (e.g. specific question is addressed. Statements, facts, and statistics are specific and accurate).? Depth of discussion (e.g. present and integrate points that lead to deeper issues)? Breadth (e.g. multiple perspectives and references, multiple issues/factors considered)? Evidence (e.g. points are well-supported with facts, statistics and references)? Logic (e.g. presented discussion makes sense, conclusions are logically supported by premises, statements, or factual information)? Clarity (e.g. writing is concise, understandable, and contains sufficient detail or examples)? Objectivity (e.g. avoid use of first person and subjective bias)

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