Epidemiology Study Guide

Epidemiology Study Guide - Epidemiology Study Guide 11-15...

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Epidemiology Study Guide 11-15 Lecture 11: Screening 1) Screening: preliminary identification of unrecognized disease or defects by the application of tests, exams, or other procedures (secondary prevention) a) Diagnosis confirms case i) Screening confirmed by diagnostic test b) Multiphasic screening (multiple tests for multiple diseases) c) Mass screening d) Selective screening (target high risk populations) e) 2) Screening criteria: a) Social: finding cases more cost effective, important health condition, acceptable screening tool b) Scientific: known biological mechanism, suitable detection test c) Ethical: improved survival, acceptable treatment present, adequate facilities 3) Evaluating Screening a) Yield amount of previously unrecognized disease that is identified ( increase with high risk population and multiple screening) b) Reliability ability of screening test to give consistent results (by reducing variability) c) Validity accuracy predicting disease i) Sensitivity (identify with disease) optimized for prevention ii) Specificity (identify those without disease) optimized for fatal untreatable diseases iii) Efficiency d) Maximize validity by increasing precision (reliability)
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e) f) Prevalence directly proportional with positive predictive value and indirectly with negative g) Predictive value looks at test status while specificity/sensitivity look at disease status 4) Efficiency: effects of end result achieved in relation to the effort in money resources 5) Efficacy : the ability to produce a desired amount of a desired effect a) Lead time bias: perception screening lengthens survival b) Length bias: cases more likely to be detected by bias if they are slowly progressive (long preclinical phase) c) Selection bias Lecture 12: Infectious Disease Epidemiology 1) Infectious disease: illness due to specific microbial agent or its toxic products (most are repotable) a) Agent: factor whose relative presence is essential for disease occurrence i) Infectious disease microorganism or microbial factor (necessary cause) ii) Agents differ in: (1) Infectivity: ability to enter and multiply in susceptible host [ (Number of infected) / (number susceptible) ] *100 (2) Pathogenicity: ability to cause clinically apparent disease [ (number with clinical disease) / (number of infected) ] * 100 (3) Virulence: ability to produce severe clinical disease or death [ (number of severe cases) / (number with clinical disease) ] * 100 (a) Case fatality: % of deaths caused by a disease among those who have disease: [ (# deaths due to disease) / (# with clinical disease) ] * 100 (4) Toxigenicity: produce toxin/poison (5) Resistance: survival (6) Antigenicity: induce antibody production
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(7) Immunogenicity: produce specific immunity b) Host: person who is infected with agent Host factors: i) Immunity can be: natural (results through having infectious agent) or artificial (by vaccine hat stimulated antibody production)
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Epidemiology Study Guide - Epidemiology Study Guide 11-15...

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