Unit 7 Case control IN EPIDEMIOLOGY.pptx

Unit 7 Case control IN EPIDEMIOLOGY.pptx

1. Epidemiology Unit vii (Epidemiological methods). Presentation topic; (discuss the analytical and basic concepts of case control) Presented to; Madam Musarat Fatima Date /14/02/2024 2/14/2024 1

2. GROUP MEMBERS ARSALAN RAJPAR ROOHULLAH NAVEED ALI PAWAN KUMAR MUHAMMAD FAISAL ASMA MUSTAFA SHAILA 2/14/2024 2

3. OBJECTIVES At the end of presentation, students will be able to; Define case control study Define case control study design. Define the steps of case control study. Advantages and disadvantages of case control. Define odds ratio and how it is calculated. Discuss impact of case control studies on public health. 2/14/2024 3

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6. Case control study Definition; A study that compares two groups of people , those with the disease or condition under study (cases) and a very similar group of people who do not have the disease or condition (controls). 2/14/2024 6

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8. Steps of case control study (1) Selection of cases and controls (2) Matching (3) Measurement of exposure (4) Analysis and interpretation 2/14/2024 8

9. (1) Selection of cases and controls Selection of cases; Diagnostic criteria; clearly define the diagnostic criteria for the disease being studied, including any specific stages(e.g . breast caner stage 1) The diagnostic criteria should be established before the study begins and should remain unchanged throughout the study. 2/14/2024 9

10. Eligibility criteria ; including only newly diagnosed (incident) cases within a specific time period. This helps ensure that cases are not old or in advanced stages of the disease (prevalent cases) and to focus on recent occurrences. (b) Sources of cases (1) hospitals; cases can be selected from hospitals, either from a single hospital or a network of hospitals, admitted within a specified period. 2/14/2024 10

11. (2) General population; in a population based control study, identify all cases of the study disease within a defined geographic area during a specified time period. Selection of controls; The proper way to select controls in a case control study involves these key consideration 2/14/2024 11

12. (a) Selection criteria; Hospital controls; they can be chosen from same hospital as the cases but with different illnesses than the disease under study. For instance, if studying cervical cancer patients, the control group might consist of patients with breast cancer, digestive tract cancer or other non related conditions 2/14/2024 12

13. (2) Relatives; T he control may also be taken up from relatives (spouses and siblings). Siblings control are unsuitable where genetic conditions are under study. (3) Neighborhood controls; The controls may be drawn from persons living in the same locality as cases, persons working in the same factory or children attending the same school. 2/14/2024 13

14. (4) General populations; population controls can be obtained from defined geographic areas, by taking a random sample of individuals free of the study disease. 2/14/2024 14

15. (2) Matching Matching involves selecting controls who are similar to cases in certain characteristics such as age, gender or other relevant factors. This helps to reduce potential confounding variables and increases the validity of the study 2/14/2024 15

16. Continue…. Matching can be done in different ways, such as individual matching or frequency matching. It is an important step to ensure a more accurate comparison between cases and controls. 2/14/2024 16

17. (3) Measurement of exposure When it comes to measuring exposure, researchers use different methods depending on the specific risk factor they are studying. For example , if they are investigating the effect of smoking on a disease, they might use self reporting or questionnaires to gather information on smoking habits. 2/14/2024 17

18. Continue… The goal is to gather accurate and reliable data to understand the relationship between the exposure and the disease outcome. Measurement of exposure is a critical step in epidemiological research to ensure valid and meaningful results. 2/14/2024 18

19. (4) Analysis The final step is analysis, to find out Exposure rates among cases and controls to suspected factor Estimation of disease risk associated with exposure (odds ratio) 2/14/2024 19

20. (a)Exposure rates A case control study provides a direct estimation of the exposures rates (frequency of exposure) to a suspected factor in disease and non disease groups 2/14/2024 20

21. (b)Relative of risk It is defined as , the ratio between the incidence of disease among exposed persons and incidence among non exposed it is given by formula; 2/14/2024 21

22. Odds ratio An odds ratio is a measure of association between a certain events ‘’a’’ and a second event ‘’b’’. Larger the odds ratio, the more likely the event is to be found with exposure 2/14/2024 22

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24. Interpretation 2/14/2024 24

25. Advantages Relatively easy to carry out Rapid and inexpensive Require comparatively few subjects. Particularly suitable to investigate rare disease or disease about which is little known. But a disease which is rare in general population(e.g. leukemia in adolescents) may not be rare in special exposure group. 2/14/2024 25

26. Continue… Allows the study of several different etiological factors (e.g. smoking and physical inactivity in myocardial infarction. Risk factors can be identified. No attrition problems, because case control studies do not follow up of individuals into the future. Ethical problems minimal. 2/14/2024 26

27. Disadvantages Selection of an appropriate control group may be difficult. Do not distinguish between causes and associated factors. Not suited to the evaluation of therapy or prophylaxis of disease. Another major concern is the representative of cases and controls. 2/14/2024 27

28. Continue…. Difficulty in determining causality Limited ability to study multiple outcomes or exposures 2/14/2024 28

29. Impact of case control study on public health Case control studies have a significant impact on public health. They play a crucial role in identifying risk factors and potential causes of disease. By examining the association between exposures and outcomes. 2/14/2024 29

30. Continue… Case control studies provide valuable information for developing preventive strategies and interventions. This knowledge helps public health professionals make evidence based decisions, implement targeted interventions and allocate resources effectively. 2/14/2024 30

31. Continue… Case control studies contribute to our understanding of disease etiology, guide public health policies, and ultimately help to improve the overall health and well being of communities. 2/14/2024 31

32. References K- park’s preventive and social medicine My AI snapchat www.google.com.pk 2/14/2024 32

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