11/4/2022 0 Comments Case control study![]() ![]() they should be at risk of becoming new cases). Controls should represent the population that the cases come from (i.e. Get this wrong and you introduce bias into the study. For rare diseases, cases may have to sought from large areas or over many years. Information on diseases can be got from death certificates, disease registers, medical records or population survey. The diagnostic criteria should be sensitive and specific (i.e. The criteria for diagnosis of a case should be defined as well as the eligibility criteria used for selection. Identification of cases can be made from the general population using health register and data or from a particular medical setting. they do not know who is a control or not). ![]() Objective measures of the presence of risk factors are best, ideally carried out in a 'blind' assessment or before the cases and controls are identified (i.e. Their selection should be independent of the exposures of interest. They should come from the same population as the cases. Define a study population (source of cases and controls)Ĭontrols must have as similar a background as possible to the cases, except that they do not have the outcome in question. If positive, it can then be tested in a cohort study.įive steps in conducting a case-control study 1. It may be the first step in testing a hypothesis.To start with a group of people with disease and work back to see whether a possible risk factor may be the cause.To determine whether or not an association exists between a disease and a particular risk factor.At the end of the study, cases and controls are defined and selenium is measured in stored samples of cases and sample of controls only. Participants are followed up and collection of mortality data is obtained. Blood samples can be taken at baseline and frozen. For example, there could be a propective study on whether low blood selenium predicts high risk of cancer. Sometimes a case-control study is nested within a cohort study. If a higher proportion of those ill report having eaten a food than those well, the food becomes suspect. ![]() Those with vomitting and diarrhoea are asked about food exposures as are those who were not ill. On a cruise ship, the population at risk is known. Outbreaks of food borne diseases are often examined by case-control studies. Unfortunately, they tend to be more susceptible to biases than cohort studies. Controls are a group without the defined outcome and are compared to cases, the group with the defined outcome.Ĭase-control studies are hard to do well and easy to do badly! They can yield important scientific findings with relatively little time, money and effort compared with other study designs. While cohort studies are sampled according to exposure, characteristic or cause, case-control studies are sampled according to disease or outcome. Starting with an outcome like disease, a case-control study looks backwards in time for exposures that might have caused the outcome. Case-control studies trace backwards from outcome to exposure. Cohorts track people forward in time from exposure to outcome. They should not be confused with historical cohort studies (also retrospective). A case-control study is an analytical observation study, i.e. Unlike experimental studies, observational studies do not look at the effectiveness of an intervention. Observational studies differ from experimental studies in that the researcher does not control the assignment of people to groups. #CASE CONTROL STUDY HOW TO#How to become a Public Health ConsultantĪ case-control study is an epidemiological study design called an observational study. ![]()
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