Experimental Study - TEO

8/13/2019 Experimental Study - TEO

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This lecture seeks to provide you with a basic understanding of

Experimental Studies, the most respected type of research study used by

Epidemiologists. Additional textbook resources can be found in thefollowing annotated bibliographies on my Web site:Annotated Biostatistics Bibliography

Annotated Epidemiology Bibliography

Annotated Research Methods

Annotated Research Practice (A - L
http://www.bettycjung.net/Biostats.htmhttp://www.bettycjung.net/Epi.htmhttp://www.bettycjung.net/Methods.htmhttp://www.bettycjung.net/Research.htmhttp://www.bettycjung.net/Research.htmhttp://www.bettycjung.net/Research.htmhttp://www.bettycjung.net/Research.htmhttp://www.bettycjung.net/Research.htmhttp://www.bettycjung.net/Methods.htmhttp://www.bettycjung.net/Epi.htmhttp://www.bettycjung.net/Biostats.htm


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Just like other scientific disciplines, Public Health support the work of

researchers in its field. Just like other academic disciplines, Public Health

includes many specialty areas, each conducting their own research, i.e.,

health education, health policy, etc. But, if you had to choose one area

that is most close to the heart of what Public Health is all about, its

Epidemiology.

While Epidemiology is the study of the distribution of disease, the

research methods used and developed by epidemiologists have been used

also to study disease-related issues. For example, health servicesresearchers look at how health services differ for different populations.

Health education researchers look at how people react to disease and

how these behaviors impact quality of life.

Thus, findings from epidemiological studies should serve as the

foundation for research in health education, health policy, etc. because a

better understanding of how disease impacts populations is crucial before

we can even think of how to better deliver services, educate people about

health behaviors, and develop rational public policy.


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It can be said, in general, that there are two main types of

studies.

Observational studies are those in which the researchers do not

interfere or manipulate any of the factors under study. They

record their observations of whats going on, and explain what

they observe with measures of association.

While we would like to say that A causes B, in order for thesekinds of studies to attempt such an explanation, there would

have to be many, many studies that observed the same chain of

events before there is a consensus that A causes B, if that.


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Interventional studies are when researchers attempt to show that A

causes B by actually manipulating those factors they think have

something to do with causing some outcome. These usually look athow well some treatment work.

In Public Health, its difficult to show that a specific factor caused a

particular outcome, when we are talking about populations. There are

usually many factors that can result in a particular outcome. And

because it is unethical to conduct testing on human subjects without

peoples consent, conducting research involving general populations is

infeasible as well. So, from a feasibility standpoint, observational

studies are more common, and if done well, can provide us with

insights on how to control disease and improve quality of life.


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Experiments, or randomized trials are used for many purposes.

Such purposes include: Assessing new screening and early

detection programs, evaluating new drugs and other treatmentsof disease, or new ways of organizing and developing health

services.

The randomized trial is considered the gold standard for

evaluating the effectiveness of therapeutic, preventive and othermeasures, both in Clinical Medicine and in Public Health.


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Observational studies include cross-sectional, case-control and cohort

studies. Of these 3 study designs, the cohort method is the preferred

design for confirming causal (antecedent) associations of healthoutcomes.

An extension of the cohort design would be an experiment to see

whether the expected outcome is found in a group receiving the

exposure (antecedent) with a control group not receiving the exposure.

A natural experiment would follow a cohort exposed to a natural

phenomenon of health consequences and then compare the health

effects in the exposed population with those not exposed to the

phenomenon.

Experimental studies are referred to as experimentalepidemiology. They are applied as clinical trials to assess the

efficacy of some intervention (or procedure), as surgical technique,

type of facility, or type of health service, to name a few. The more

common term used in Epidemiology is randomized trial.


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This is the basic strategy behind an experimental epidemiological

study. To show that a treatment is effective, the improvement rate in a

treated group (T) should be greater than the improvement rate in theuntreated group (NT), and that the differences in rates should be

unlikely they are due to chance.

The control group (NT) should be similar to the treatment group (T) in

all characteristics associated with the expected outcome (recovery),

and should not receive the studied treatment. The control group maybe receiving the prevailing, or current standard of care, or a placebo.


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To cover the basics, I am trying to keep this as simple as possible.

Randomized trials, especially clinical trials, can become very complex,

with many groups (arms) involved in one study. Regardless of how manygroups are in a study, random allocation (or randomization) is used to

ensure the groups are comparable.

In matching, the researcher may match for, say, race and sex. So for a

matched pair of white females, the researcher would then randomly

assign one subject to the treatment group and the other to the controlgroup. After all the matched pairs have been assigned, the two study

groups would then have the same race and age distribution, as well as

about the same distribution for other variables because of random

allocation.


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This graphic shows when random allocation (randomization) should take

place during the study process. Basically, the researcher starts with adefined population that is randomized to a new treatment or current

treatment. The subjects are then followed to see how many improve for

the new treatment and current treatment. Sometimes a treatment may be

compared to no treatment, but this is very rare. If there is already a

treatment in place, it is best to compare the new treatment to a treatment

already in place.

Randomization increases the likelihood that the groups will be

comparable in regard to characteristics that may affect prognosis. Such

characteristics include sex, age, race and severity of disease.Then again randomization isnt a guarantee of comparability because

chance does play a role in the process. In the long run, the groups tend to

be similar. Finally, randomization is ethical only when we do not know

whether one treatment is better than the other.


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Despite the negatives, randomized controlled studies are still considered

the gold standard of clinical research. If done right, results, whether good

or bad, contributes to the collective scientific body of knowledge.


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Experimental Study - TEO

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