Epidemiology 101 Study Guide.docx - Agazit Tesfai...

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Agazit Tesfai Epidemiology 101 Study Guide Chapter 3 The Occurrence of Disease I. Disease Surveillance and Measures of Morbidity This chapter discusses surveillance in populations and its importance in providing information about morbidity from disease. Also, we will cover how we use rates and proportions to express the extent of morbidity from disease. SURVEILLANCE Surveillance: “ongoing systematic collection, analysis, and interpretation of health data essential to the planning, implementation, and evaluation of public health practice closely integrated with the timely dissemination of these data to those who need to know.” Monitor changes in disease frequency or levels of risk factors Two types: Passive and Active o Passive- available data on reportable diseases used (responsibility on health care provider or district health officer). Completeness of data depends on these individuals so underreporting usually common. Local outbreaks can be missed because small number of cases diluted by large denominator. Relatively inexpensive o Active- project staff recruited to carry out surveillance program (field visits to health care facilities, interviews, reviewing medical records, surveys). More accurate, but more expensive Surveillance can also be carried out to asses changes in levels of environmental risk factors of disease (Like particulate air pollution). May give warning about possible rise in rates of disease associated with environmental agent STAGES OF DISEASE IN AN INDIVIDUAL AND IN A POPULATION Source of data (hospital, individual, health insurance company) greatly affects calculated rates Timeline: Disease onset—Symptoms—seek care—diagnosis—Treatment. Outcome may be cured, controlled, disabled, or death Rate: how fats disease is occurring in population Proportion: what fraction of the population is affected by disease
Chapter 4 (61-75) The Occurrence of Disease II. Mortality and Other Measures of Disease Impact This chapter discusses quantitative expression of mortality and the uses of such measures in epidemiologic studies MEASURES OF MORTALITY Absolute numbers do not give us meaningful information, must use rates (numerators and denominators) MORTALITY RATES Annual death rate = Totaldeaths ¿ allcauses 1 year ¿ Number of persons the populationat midyear x 1,000 Population changes over time, so population at midyear used May modify this equation to look at specific age or gender or disease etc but must change both numerator and denominator to fit criteria We multiply by 1,000 to find number of deaths per 1,000 individuals, can choose any number (usually multiply by number that makes answer a whole number) Specific rates Age-specific death rate = Total deaths ¿ allcauses 1 year kid < 10 yrs ¿ Number of persons the population < 10 yrs at midyear x 1,000 Disease-specific death rate = Total deaths ¿ lungcancer 1 year ¿ Number of persons the populationat midyear x 1,000 CASE-FATALITY Case-fatality (percent) = ¿

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