Classification of mediation analysis methodology in clinical research – Pubrica

1. CLASSIFICATION OF MEDIATION ANALYSIS METHODOLOGY IN CLINICALRESEARCH An Academic presentationby Dr.NancyAgens,Head,TechnicalOperations,Pubrica Group: www.pubrica.com Email:sales@pubrica.com

2. Today'sDiscussion Outline InBrief What is MediationAnalysis Classification of Mediation Analysis Methodology Conclusion FutureScopes

3. InBrief Mediation Analysis as a method to connect the causal-effect relation in being used popularly in Medical writing for clinical research, specially since the last decade. The type of Mediation Analysis model is dependent on the needs of the study and each has its own set of advantages and disadvantages. Since there is significant heterogeneity in the manner it is used, there is need for methodologicaluniformity.

4. Mediation analysis (MA) is a form of statistical analysisand is very commonly used in epidemiology, psychology, sociology, and medicine by Scientific Medical WritingCompanies. What is Mediation Analysis? It attempts to predict the relation between the antecedent variable and the outcome variable by Clinical ResearchServices. In other words, Medical Writing in Clinical Research use MAto try and find methodology by which outcome is related toexposure. Thus, it is useful in both interventional and observational studies while scientific research paper writing or Medical Writing for ClinicalTrials.

5. Research paper writing help use mediation model as a causal model where mediator is presumed to cause the effect, while the vice versa is nottrue. Statistics is used to evaluate whether the presumption of the MA is correct ornot. Scientific writing help use this information while research paper writing and it is useful to find the association withcausation. This helps understand the disease aetiology better and this information is used to improve or alter existing treatment and managementmodality.

6. Classification of Mediation Analysis Methodology 1.TRADITIONAL APPROACHES SINGLE MEASURE:- In this method, separate regression models are used for the antecedent and the outcome variable in clinical medical research.E.g. Baron and Kenny’s framework is commonly usedby Medical ResearchCompanies. X is the causal variable and Y is the outcome in the absence of any mediation as per the below representation. Path C is the totaleffect. Contd..

7. Mediating variable M in the below figure is the process or interventionvariable. Path C´ in this figure is the direct effect. When the path from X to Y is reduced but above zero, there is partial mediation, while when C´ becomes zero, there is complete mediation. There are four steps in the Baron and Kenny’s modelin establishingmediation. Contd..

8. Step 1: - To show that the antecedent variable correlates with the outcomevariable. Step 2: - To show that the antecedent variable correlates with themediator. Step 3: - To show that the mediator affects the outcomevariable. Step 4: - To establish that the mediator completely mediates the causal- effect relationship. Total effect = direct effect + indirect effectOR C = C´ +ab Complete mediation is proved when all the four steps are met, while partial mediation is indicated if Step 4 is not met. Contd..

9. Contd..

10. 2.COUNTERFACTUAL APPROACHES SINGLE MEDIATOR:- Lewis’s 1973 counterfactual analysis is based on the understanding that, if an antecedent event is the complete causal factor for the effect, then, there would not be the effect if there is no antecedentevent. Medical Writing CROuse different regression modelsfor the antecedent and the outcome. Causal contrast is highlighted between the exposed and thenon-exposed. In the causal-effect model, when there are multiple mediators that need to be evaluated, one can consider one mediator at atime. This is possible only when mediators do not affect eachother. Contd..

11. However, if we need to evaluate several mediators simultaneously or in cases where mediators affect each other, we need to use either parallel or serialMA. Contd..

12. Mediation with single mediator M, A is exposure, Y is the outcome and C is theconfounder. Contd..

13. Mediation with two mediators M(1), M(2), A is exposure, Y is outcome and C is theconfounder. Contd..

14. Mediators with unknown common cause, where mediators do not affect eachother. Contd..

15. PARALLELMEDIATORS: Medical Writingfor Clinical researchuses parallel multiple mediators that need to be evaluated at the sametime. Regression model is used for all mediators and separate models are used for differentmediators. SERIAL OR SEQUENTIAL MEDIATION:- Serial mediation is used when mediators act one after the other for the outcome or the chainreaction. Contd..

17. Conclusion MA is a statistical technique which is beingused increasingly by Research Paper Writing Services andMedical Writingin ClinicalTrials. There is no single approach to MA, researchers may ormay not have a priorhypothesis. Scientific research writing help may focus on direct orindirect antecedent causal evidence or association-basedstudies. Each model of MA has its own advantages anddisadvantages and the model chosen depends on the type ofstudy.

18. Future Scopes MA is based on strong assumptions that need tobe discussed to avoidmisinterpretations. Planning MA in advance is preferred as it helps inadjusting in the methodologies to account for appropriate samplesize, key confounders, and measurement errors inmediators. There is considerable heterogeneity in the planning,conduct and reporting of MA, necessitating the need to have uniform and consensus-based guidelines on themethodology.

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