lec5_jls

lec5_jls - BE.104 Spring Epidemiology Test Development and...

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BE.104 Spring “Epidemiology: Test Development and Relative Risk” J. L. Sherley Agent X Health ? Cause First, Some definitions Morbidity = sickness, disease, [toxicity] – Hard to quantify Mortality = death – Easy to quantify Annual Death Rate = Total deaths during specified 12 months Number of persons in pop. @ middle of the period specified Age-specific ADR = ADR for a specified age Age-adjusted ADR = adjusted ADR (indexing for age differences, e.g., death rates in nursing home versus general population) Incidence = # of NEW cases in a population during a specified period of time = “Rate of appearance in group at risk” Number of persons exposed to risk of developing disease in same interval (by convention per 100,000 persons) Prevalence = # of cases in population at a specified time = “Frequency” # of persons present in pop. at same time (By convention per 100,000 persons) [Prevalence α Incidence X duration of disease based on death or cure] “Chronic disease will be more prevalent” 1
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Tests d i s e a s e To determine these epi-parameters, we need to develop tests to detect and quantify exposure d e a t h Develop tests - Disease measurements (death is not all that easy to quantify when you want death from a specific cause) - Exposure measurements to X - Measure X in the environment Properties of a good test Simple Well tolerated < by all involved; subject & tester > High throughout Proven versus newly developed Precise Accurate: Sensitive, Specific, Predictive 2
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Categories of test results w/D w/oD <Disease (D) Status Positive Negative <Test TP FP FN TN True positives, TP False positives, FP False negatives, FN True negatives, TN Sensitivity = TP x 100%; Ideally, = 100% TP + FN FN = 0 (All the affected) Sensitivity = the efficiency at detecting cases Specificity = TN x 100%; Ideally = 100% TN + FP FP = 0 (All the unaffected) Specificity = efficiency at identifying non-cases Predictive value (PV):
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This note was uploaded on 11/11/2011 for the course BIO 20.010j taught by Professor Lindagriffith during the Spring '06 term at MIT.

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lec5_jls - BE.104 Spring Epidemiology Test Development and...

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