E-quiz 3a
Terms
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- More issues in cohort studies (disease status)
- Determination of disease status at intake or start of study persons with history of outcome disease, or current outcome disease must be excluded consistency and accuracy of this ascertainment is very important
- More issues in cohort studies (# of events)
- Actual number of events expected and observed what is anticipated incidence in exposed and unexposed sample size for study completeness of disease ascertainment
- Analysis & interpretation
- Computing incidence (Cum Incid and/or ID) Computing relative and absolute risks Assessing threats to validity non-response bias follow-up bias confounding
- Disadvantages
- not good for diseases of low incidence potential for follow-up bias time-consuming expensive
- Advantages
- rare exposures can be examined wide array of potential outcomes temporal relationship clear allows for direct determination of absolute risk of disease
- Quality of info
- Quality of information on exposure and disease accurate and complete exposure information consistency of source for both exposed and non-exposed reassessment of exposure in follow-up maintaining high level of follow-up
- Retrospective recruitment
- Retrospective cohort recruitment industrial settings with exposure of interest other settings with groups of individuals that have extended periods of follow-up, e.g. HMOs, military, etc.
- Prospective recruitment
- Prospective cohort recruitment cross-sectional survey as initial phase, with recruitment into cohort as second phase explicit solicitation of persons with a specific exposure recruitment of members of organized groups of persons with and without exposure
- ID & selection of comparison pop
- Identification/selection of the comparison population similar to exposed except for exposure information on exposure and disease status is available feasibility of follow-up
- ID & selection of exposed pop
- Identification/selection of the exposed population frequency or prevalence of exposures quality of exposure information feasibility of follow-up
- Example 1
- A retrospective study of a variety of health outcomes thought to be associated with Agent Orange in the Vietnam War. Companies of soldiers were selected on the basis of their exposure to Agent Orange by duty cycles and assignments, their medical records were reviewed and they were screened for the outcomes of interest.
- Example 2
- A prospective study of the residents of Framingham MA followed adult male residents for more than 2 decades. Lifestyle and health status variables were measured every year or two by questionnaire and/or examination. Risk factors for heart disease were the primary focus.
- Example 3
- A prospective study of HIV risk in a sample of HIV negative female prostitutes in Kinshasa, Zaire followed women for 3 years. Data were gathered at baseline and every 3 months on risks (including sexual behavior and STD infections). HIV status was also tested every 3 months.
- Analytic studies defn
- Used to test specific hypotheses and relationships between diseases and possible determinants