Prevalence Is A Point Based Estimate Essay

2100 Words Oct 18th, 2016 9 Pages
Prevalence is a point-based estimate, so although at the time of the survey they may have Tb, by the time the study started they may have recovered. Including these people would overestimate the effect as there will be more ‘cases’ than in reality. Alternatively, the results could be underestimated as it is likely that more people will have developed Tb since the survey was conducted. Furthermore, using a point-based estimate like prevalence to obtain cases means that the data will only be valid for that time period. This means that the results will be over or underestimated, but also not generalizable to other time periods, which affects external validity of the study.

Yes: Studying the 85,474 persons identified by the prevalence survey in a resource poor setting is unrealistic. A case-control study can match cases and controls by age and sex, which have been issues in previous studies. Less expensive and time-consuming than including everyone. Information on biomass fuels is difficult to obtain. Testing for Tb can be expensive.

“…all persons in the selected villages/units were registered via door-to-door census”.1 Cases were selected from a population-based study and confirmed by positive sputum smears/positive culture. Controls were selected from the same population-based survey.

Controls came from the same survey and village as cases – if they had Tb, they would have been cases. All households were included in the survey and as controls were selected…

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