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CASE CONTROL STUDYDr. Muhammad Tareque HasanTeaching AssistantDepartment of EpidemiologyBUHS
•At the end of the lesson we shall be able to understand-1. Types of epidemiological study2. What is case control study3. Design and steps of (how to conduct) case control study4.Features and characteristics of case control study5.Characteristics and qualities of controls7. Selection criteria of case and control8. Advantage and disadvantage of case control study9. Difference between case control and cohort study10.Some important discoveries of case control study.11. How to calculate odds ratios.Case control study
Epidemiological Study CycleDESCRIPTIVE STUDY •Ca Lung increasing mostly smokers•Death rates higher in populations with higher per capita cigarette consumptionOchsner, 1939CASE CONTROL STUDY•Ca Lung patients and non patientsClarifies if it was smokers who contributed to high Ca LungDoll, 1947-52COHORT STUDY•Follows a cohort of smokers and non smokers without Ca Lung•Smokers develop Ca Lung more frequentlyINTERVENTIONAL TRIAL (RCT)•Proves hypothesis conclusively•Gives inputs regarding other factors, control measures. Hypothesis: Smoking causes Ca LungHill, 1951-61
Analytical Studies•Observational•Case control (Retrospective) studies•Cohort (Prospective) studies•Experimental(Interventional):•Animal experiments•Human studies•Therapeutic trials•Preventive trialsDifference in study groups is ONLY observed & analysed, NOT created experimentallyDifference in study groups is CREATED EXPERIMENTALLY and outcomes observed
Case control study
Case control study•Case control studies often called “retrospective studies” are common first approach to test causal hypothesis.The occurrence of the possible cause or exposure to a certain factor is compared between a group of person who have the disease of interest (case) with suitable matched group of person without the disease(controls). In case control studies the unit of study is individual rather than the group.The focus is on a disease or some other health problem that has already developed
Case control study cont……•Case control study has three distinct features:1.Both exposed and out come (disease) have occurred before the start of the study.