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Classification of Mediation Analysis Methodology in Clinical Research

Dr. Nancy Agens, Head,

Technical Operations, Pubrica

sales@pubrica.com

In Brief

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

methodological uniformity.

Keywords

Scientific Medical Writing Companies,

Medical Writing In Clinical Research,

scientific research paper writing, Medical

Writing for Clinical Trials, Medical

Writing in Clinical Trials, Clinical

Research Services, Medical Writing CRO,

research paper writing service, Medical

Writing for Clinical research, research

paper writing help, Scientific Writing

Help, clinical medicine research, medical

research companies.

I. WHAT IS MEDIATION ANALYSIS

Mediation analysis (MA) is a form

of statistical analysis and is very

commonly used in epidemiology,

psychology, sociology, and medicine by

Scientific Medical Writing Companies. It

attempts to predict the relation between the

antecedent variable and the outcome

variable by Clinical Research Services. In

other words, Medical Writing in Clinical

Research use MAto try and find

methodology by which outcome is related

to exposure.Thus, it is useful in both

interventional and observational studies

while scientific research paper writing or

Medical Writing for Clinical Trials.

Research paper writing help use mediation

model as a causal model where mediator is

presumed to cause the effect, while the

vice versa is not true. So, wherever the

presumption is not correct, MA is not

useful. Statistics is used to evaluate

whether the presumption of the MA is

correct or not.

Scientific writing help use this

information while research paper writing

and it is useful to find the association with

causation. This helps understand the

disease aetiology better and this

information is used to improve or alter

existing treatment and management

modality.

II. CLASSIFICATION OF MEDIATION

ANALYSIS METHODOLOGY

There following are the methods used in

MA:

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

used by Medical Research Companies.

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 total

effect.

Mediating variable M in the below

figure is the process or intervention

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variable. 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 model in establishing

mediation.

Step 1: - To show that the antecedent

variable correlates with the outcome

variable.

Step 2: - To show that the antecedent

variable correlates with the mediator.

Step 3: - To show that the mediator

affects the outcome variable.

Step 4: - To establish that the mediator

completely mediates the causal- effect

relationship.

Total effect = direct effect + indirect

effect OR

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.

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 antecedent event.

Medical Writing CRO use different

regression models for the antecedent

and the outcome. Causal contrast is

highlighted between the exposed and

the non-exposed.

In the causal-effect model, when

there are multiple mediators that need to

be evaluated, one can consider one

mediator at a time. This is possible only

when mediators do not affect each other.

However, if we need to evaluate several

mediators simultaneously or in cases

where mediators affect each other, we

need to use either parallel or serial MA.

Mediation with single mediator M, A is

exposure, Y is the outcome and C is the

confounder.

Mediation with two mediators M(1)

, M(2)

,

A is exposure, Y is outcome and C is the

confounder.

Mediators with unknown common cause,

where mediators do not affect each other.

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Mediators with unknown common cause,

where mediators affect each other.

3. Parallel mediators: Medical Writing for

Clinical research uses parallel multiple

mediators that need to be evaluated at

the same time. Regression model is

used for all mediators and separate

models are used for different

mediators.

4. Serial or sequential Mediation: - Serial

mediation is used when mediators act

one after the other for the outcome or

the chain reaction.

An example of a sequential MA is a

survey study conducted on Chinese

university students linking indicators

of career adaptability in the context of

changing job scenario and challenges

faced by Chinese university students

while seeking jobs or building their

careers.

III. FUTURE SCOPES

MA is based on strong assumptions

that need to be discussed to avoid

misinterpretations. Planning MA in

advance is preferred as it helps in adjusting

in the methodologies to account for

appropriate sample size, key confounders,

and measurement errors in mediators.

There is considerable heterogeneity in the

planning, conduct and reporting of MA,

necessitating the need to have uniform and

consensus-based guidelines on the

methodology.

IV. CONCLUSION

MA is a statistical technique which

is being used increasingly by Research

Paper Writing Services and Medical

Writing in Clinical Trials. There is no

single approach to MA, researchers may or

may not have a prior hypothesis. Scientific

research writing help may focus on direct

or indirect antecedent causal evidence or

association-based studies. Each model of

MA has its own advantages and

disadvantages and the model chosen

depends on the type of study.

REFERENCES

1. MacKinnon, D. R., Kisbu-Sakarya, Y., &

Gottschall, A. C. (2013). Developments in

mediation analysis. In T. D. Little (Ed.), Oxford

library of psychology. The Oxford handbook of

quantitative methods: Statistical analysis (p. 338–

360). Oxford University Press.

2. VanderWeele, T. J., & Vansteelandt, S. (2014).

Mediation Analysis with Multiple

Mediators. Epidemiologic methods, 2(1), 95–115.

3. Zhuang Mingke, She Zhuolin, Cai Zijun, Huang

Zheng, Xiang Qian, Wang Ping, Zhu Fei (2018).

Examining a Sequential Mediation Model of

Chinese University Students’ Well-Being: A Career

Construction Perspective. Frontiers in Psychology,

9, 593.

4. Tat-Thang Vo,Cecilia Superchi,Isabelle

Boutron,Stijn Vansteelandt (2020). The conduct and

reporting of mediation analysis in recently

published randomized controlled trials: results from

a methodological systematic review. Journal of

Clinical Epidemiology,117,78-88.