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Calculation Exercise –Measures of RiskA team of Epidemic I

    Calculation Exercise –Measures of RiskA team of Epidemic Intelligence Service officers from theCDC arrives in Rhode Island to assist the state health department withinvestigation and control of an outbreak of measles.  The team is asked to include the entire statein the investigation; thus, the case definition for measles in this outbreak isany resident of Rhode Island meeting the clinical case definition (>= 102deg fever + rash + either cough, coryza, or conjunctivitis) who either has apositive laboratory test for measles IgM antibody or is a contact of someonewith a positive test.  Individualsmeeting the clinical case definition who did not have laboratory confirmationand were not contacts were classified as “possible cases”.  The team members arrive in Rhode Island on March 1st.  They discover 13 individuals who met theclinical/laboratory case definition with dates of rash onset in February.  Ten of these 13 are Rhode Island residents,the other three are residents of neighboring states who were seen and treatedat Brown University Medical Center in Providence, RI.  Nine of these 10 were still ill as of March 1.  The tenth, the probable index case for theoutbreak, was a teenager who had traveled to Europe and returned three daysprior to her rash onset.  She hadrecovered from her illness by the time the investigative team arrived.During March, 31 additional Rhode Island residents werediscovered who met the clinical case definition for measles, with rash onsetson or after March 1st.  Twenty-threeof these had laboratory confirmation and 6 others were contacts of those whohad.  An extensive statewiderecord-checking and vaccination program was undertaken throughout March,focusing on those schools, communities, and other settings where cases hadoccurred.  Only two of the cases had rashonset in the last week of March.For the purposes of this exercise, use one million for theRhode Island state resident population.1) What was the prevalence of measles in RhodeIsland as of March 1st? 132) What was the incidence of measles in RhodeIsland for March?3) What would the incidence be if possible caseswere included?4) If all but two of the February cases, and sevenof the March (confirmed) cases had recovered by March 24, what would theprevalence have been as of that date? Six thousand veterans of the armed services were recruitedfor a longitudinal, prospective cohort study of smoking-related cancers.  At the beginning of the study, a combinationof interview and urinary cotinine tests ascertained that 1,450 of the veteranswere current smokers.  An additional1,935 veterans in the cohort had been regular smokers at some time in theirlives but had quit (no cigarettes in the last 30 days) by the beginning date ofthe study.  None of the cohort membershad any form of cancer as of the study start date.During the five years of the study (for the purposes of thisexercise we will make the very unrealistic assumption that none of the 6,000veterans died nor were lost to follow up for the entire five years) lung cancerdeveloped in 36 veterans who were current smokers, 18 who were former smokers,and 2 who had never smoked.  Bladdercancer developed in 10 current smokers, 11 former smokers, and 5non-smokers.  All other forms of cancercombined developed in 41 current smokers, 24 former smokers, and 22non-smokers.  5) What was the incidence of lung cancer overall?6) What was the incidence of lung cancer insmokers, former smokers, and non-smokers?7) What was the incidence of bladder canceroverall?8) What was the incidence of bladder cancer insmokers, former smokers, and non-smokers?9) What was the incidence of all types of cancercombined, overall?10) What was the incidence of all types of cancercombined, in smokers, former smokers, and non-smokers?11) What was the relative risk of lung cancer insmokers compared to non-smokers?12) What was the relative risk of lung cancer informer smokers compared to non-smokers?13) What was the relative risk of bladder cancer insmokers compared to non-smokers?14) What was the relative risk of bladder cancer informer smokers compared to non-smokers?15) What was the odds ratio of all other forms ofcancer in smokers compared to non-smokers?16) What was the odds ratio of all other forms ofcancer in former smokers compared to non-smokers?17) What was the odds ratio of all types of cancercombined, in smokers compared to non-smokers?18) What was the odds ratio of all types of cancercombined, in former smokers compared to non-smokers?19) For #17 and #18 only, how closely does the oddsratio approximate the relative risk for smokers?  For former smokers?  Why?20) What was the attributable risk of lung cancer insmokers (compared to non-smokers)?21) What was the attributable risk fraction of lungcancer in smokers?22) What was the population attributable risk oflung cancer due to current smoking in this population (compared tonon-smoking)?23) What was the population attributable riskfraction of lung cancer due to current smoking in this population (compared tonon-smoking)?   24) Why is the PAR fraction less than the ARfraction?  How do you think the PARfraction would be  different if thisstudy were done in the general population rather than in a population ofveterans?

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