Types of clinical studies

Thomas Abraham

Three broad types of studies: used for different purposes

1. Observational (observe groups of people, gather data, but does not make any kind of intervention)

2. Experimental studies ( makes an intervention)

3. Meta studies: takes data from a large number of studies and compares them, providing results that are stronger than individual studies

Observational studies

1. Cross sectional ( measures or surveys data at a point in time)

Eg: Opinion survey of nurses in Hong Kong about H1N1 vaccination; measuring obesity in teenagers

Typically used to study prevalance of a disease or condition ( not causes of a disease or condition)

Observational Studies

2. ) Case control studies-Patients with a particular disease or condition are matched with a similar group of people without the disease, and then data is collected from both groups about past exposure or behaviour.

Cannot really determine cause and effect, but useful for generating hypotheses based on the statistical associations

Observational studies

3. Cohort studies: A group of people without the disease being studied are chosen, their habits, or other variables, are recorded over a long period of time, to see who develops the disease and who does not. Associations are then made between habits and the disease.

This is the strongest observational method for trying to determine cause and effect

Experimental studies

Randomised controlled trial: gold standard of causality

Used to evaluate new treatments Subjects are randomly allocated to

intervention (gets new treatment and control( does not get new treatment) groups

Both groups should be as similar as possible

Double blind= neither subject nor researchers know who is getting what

Meta Studies

Looks the results of a wide range of published studies; regarded as high evidence value

Evaluating studies

Is it still at the animal or laboratory stage, or human stage?

Where published? peer reviewed journal, scientific meeting or press release/conference?

How big were the numbers tested? How relevant are the findings-is it of

immediate benefit for people What will it cost? Conflicts of interest

How big were the numbers tested? How relevant are the findings-is it of

immediate benefit for people What will it cost? Conflicts of interest