Cross sectional study

The slide about one of the study design method cross-sectional design

1. Title:- Cross sectional study 23-Feb-21 1

2. Study Design A study design is a plan for selecting study subjects and for obtaining data about them. A research design is the blueprint for conducting a study that maximizes control over factors that could interfere with the validity of the findings . There are different category of study types: - descriptive studies, A nalytical studies, and E xperimental studies. 23-Feb-21 2

3. Diagrammatical representation Study design Descriptive Case report survey Case series Analytical Cohort case-control Cross-sectional Laboratory Field research observational Experimental 23-Feb-21 3

4. Analytical study Analytical studies are undertaken to test a hypothesis and the association between an exposure of interest and a particular outcome hypothesis typically concerns whether a certain exposure causes (or is associated with) a certai n outcome 23-Feb-21 4

5. Most frequent researches are done in the form of observational studies . Observational study can be Retrospective = outcome occurred before study starts Prospective = no out come occurred before study starts It do not interfere with the phenomena under study, only observe in a systematic and standardized manner 23-Feb-21 5

6. In observational studies normally three types of study design are used: - Cross-Sectional ( prevalence study) Case-control (Compares diseased animals ( cases ) with non-diseased animals ( controls )) Cohort Studies (Follow the groups through time to determine if disease develops) Also Called Incidence. 23-Feb-21 6

7. Cross sectional study What are cross-sectional studies ? Described as a “ snapshot ” of a population in a certain point of time because exposure and outcome are determined simultaneously for each subject . It is an observational study. It is also called prevalence study. 23-Feb-21 7

8. Diagrammatical representation of cross sectional Study 23-Feb-21 8

9. Con’t … Cross-sectional study measure simultaneously the exposure and health outcome in a given population and in a given geographical area at a certain time . cross-sectional studies are very useful in descriptive studies when used in studies that are proposed to be analytical. 23-Feb-21 9

10. C ross sectiontional con’t …. The aim of cross-sectional studies is to obtain reliable data that make possible to generate , robust conclusions , and create new hypotheses that can be investigated with new research. The main characteristic of cross-sectional studies is that the observation of variable . Whether they are cases , individuals, or other types of data, is performed in a single moment. 23-Feb-21 10

11. Prevalence of disease and exposure can be calculated by 2x2 table Disease Non D isease Exposed Non exposed Prevalence of exposure in diseased compared to non-diseased: a/ a+c vs b/ b+d Prevalence of disease in exposed compared to non-exposed: a/ a+b vs c/ c+d a b c d 23-Feb-21 11

12. Applications of cross-sectional studies They are usually conducted to estimate the prevalence of the outcome of interest for a given population, commonly for the purposes of public health planning. Appropriate for screening hypotheses because they require relatively shorter time and fewer resources . Also used to understand the prevalence of various conditions, treatments , services or other outcomes and the factors associated with such outcomes. 23-Feb-21 12

13. Advantages of cross-sectional studies Relatively inexpensive T akes little time to conduct( quick) serve as a basis for calculating sample size in the planning of future analytical research Can estimate prevalence of outcome of interest because sample is usually taken from the whole population . 23-Feb-21 13

14. Advantage con’t … Many outcomes and risk factors can be assessed. Useful for public health planning, understanding disease etiology and for the generation of hypotheses . There is no loss to follow-up . No risk to subjects Current records occasionally can be used 23-Feb-21 14

15. Disadvantages of cross-sectional studies Cannot tell us about causal relationships (only correlation ). Temporal sequence of cause and effect cannot necessarily be determined Only suitable for chronic conditions occurring at a moderate level in the population Unsuited to the study of rare diseases Unsuited to the study of diseases of short duration Generalizability limited by sampled population and population definition. 23-Feb-21 15

16. Disadvatage con’t … Sample size requirements may be very large (especially when looking at rare outcomes or exposures). It evaluates prevalence rather than incidence Potential for selection bias ( systematic differences between characteristics of the study population and the target population from which it was drawn) Most observational studies use data gathered from convenient populations such as veterinary clinics, abattoirs and particular farms (inference be made with great care) 23-Feb-21 16

17. Conclusion Cross-sectional studies :- have their great use in descriptive studies used for public health planning , understanding disease etiology and for the formulation of hypotheses . Relatively cheap observational studies and can be conducted in a short time. cannot be used to establish causal relationship between exposure and outcomes . 23-Feb-21 17

18. Comparison of cross-sectional with cohort study 23-Feb-21 18

19. Summary of observational study 23-Feb-21 19

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