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By Diane Griffith, HealthAtoZ writer
You're watching the news and you hear about a new study that could affect you or a loved one. Of course, you want to find out more. Chances are, though, that trying to understand the study mentioned in the newscast is going to leave you with more questions than answers. Here are some pointers to help you translate that scientific jargon into plain English.
Randomized trials
There are several types of studies. The most reliable is the randomized control trial (RCT). An RCT has:
- A treatment group. One group of people receives experimental treatment, like a new medication.
- A control group. The control group doesn't get the new medication or therapy. Instead they may receive the standard therapy or a placebo (sugar pill).
- Randomly chosen participants. Neither the subjects nor the researchers choose who goes into which group.
An RCT will often have these features:
- It is doubled blinded. Neither the subjects nor the researchers know which patients are in which group.
- It has a large sample size. Many people are tested.
- Subjects are followed over a long period of time (this can be for years - or even a lifetime - depending on the study).
Case control and cohort studies
Case control and cohort studies are a step below the RCT. A case control study looks for a common link by comparing people who've had a certain disease with people who haven't. For example, if some passengers on a cruise ship came down with food poisoning and others didn't, a case control study would compare the types of foods eaten by each group.
A cohort study looks at people who've been exposed to a certain risk and compares them to people who haven't. The group is followed to see what happens to them in the future. For example, researchers may study children who've been exposed to secondhand smoke and children who haven't - and later compare the cancer rates between the two groups.
Other types of studies
The evidence provided in the following studies isn't as strong as in the RCT, case control study or cohort study.
- Cross-sectional study. Looks at a single point in time.
- Example: Comparison between overweight and thin adults to determine which group more often develops diabetes.
- Ecological study. Compares disease rates in different populations.
- Example: Comparison of cavity rates among children in two different towns with two different fluoride levels in the water.
- Meta-analyses. Instead of working with patients directly, researcher reviews medical literature for similar studies, then combines the results.
- Case reports. Describes the symptoms of a patient with puzzling symptoms. When AIDS first appeared, so did numerous case reports describing its symptoms.
Trials
A trial is a study that tests a drug or medical device to see if it's safe.
Protocols
All clinical studies are based on a set of rules known as protocols. They describe such things as the types of people who will participate in the study, the schedule for providing tests and medications, and the length of the study.
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External Sources
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PatientINFORM.org
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National Human Genome Research Institute - National Institutes of Health
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This article was reviewed and updated June 2007.
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