unit 12 pt 1 - Unit 12: Overview Unit 12 Screening in...

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Unit 12 Screening in Epidemiology Screening and evaluation of diagnostic tools Dr. A. Sanchez-Anguiano Epidemiology 6000 Unit 12: Overview ± Understand purposes of screening and why screening is important ± What part of the natural history of disease does screening affect? ± Requirements “prices” and consequences of screening on morbidity Requirements, prices , and consequences of screening on morbidity ± Desirable characteristics of a screening test ± Validity: sensitivity and specificity and their inter-relationship ± Consequences of setting the cut point too low or too high ± What are receiver-operating characteristic curves and why are they used ± Reliability of screening tests ± Measuring the performance (yield) of screening tests: PVP and PVN ± Relationship between yield and prevalence of the disease in the population ± Sources of bias in evaluating screening programs: volunteer bias, lead-time bias, length bias Screening Definition: The application of a test to people who are as yet asymptomatic (search for subclinical disease; detect disease). Systematic testing of asymptomatic individuals for preclinical disease. Purpose : To classify individuals with respect to their likelihood of having a particular disease. To prevent or delay development of advanced disease in a subset of patients with preclinical disease through early detection and treatment. Screening ± Screening procedure itself does NOT diagnose illness. ± Screening = PH interventions among populations ( tool for detection ) ± Diagnosis = Clinical intervention applied to individual Usually used for diseases in which ± Usually used for diseases in which ± some treatment or prevention can be applied , ± to find cases for prevalence and incidence studies for prevalence and incidence studies. Screening for Disease Control ± Examination of asymptomatic people (screen +) likely Classification a ± Classification as (screen - ) unlikely ….. to have a disease Screening for Disease Control “Unlikely” referred to next screening cycle “Likely” further testing for diagnosis Diagnosed Not Diagnosed Referred to next Treatment screening cycle
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Screening for Disease Control ± Screening objective : ± Operationally : application of a relatively simple, : application of a relatively simple, inexpensive test to a large number of persons in order to classify them as likely or unlikely to have the disease that is the object of the screen. ± In terms of outcome is to lower morbidity and mortality of disease in a screened population, at a reasonable cost. ± Screening provides access to the medical care system which is not an actual goal of screening, but is a benefit. Screening for Disease Control Screening is important because: 1) Whil ti l i ( i k f t ) di ti d While etiologic (risk factor), diagnostic and therapeutic advances take many years and progress may be slow screening may provide a “direct solution” may be slow, may provide a direct solution to modify the history of a disease in a population; 2) Screening
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This note was uploaded on 07/15/2011 for the course PHC 6000 taught by Professor Staff during the Summer '08 term at University of South Florida - Tampa.

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unit 12 pt 1 - Unit 12: Overview Unit 12 Screening in...

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