An unintended or unanticipated effect of treatment which results in negative consequences to study participants.
A study in which a specified outcome is compared in groups of people who are alike in most ways but differ in one particular characteristic.
A group of study participants or objects that are not exposed to the entity being tested.
A clinical trial in which the study participants receive both the treatment being tested and the control. They may be assigned either the treatment being tested or the control first, then later switch to the other. By doing a crossover, each patient serves as their own control.
A study conducted at a particular point in time, not over the course of time (e.g., a study which determines the prevalence of arthritis at a particular point in time).
A study in which neither the study participants nor the investigators know which group is given the treatment/medication being tested or the placebo.
Studies that are extended for a longer duration beyond the initial trial period.
In a clinical study, a healthy control is a research subject who is generally healthy and does not have the disease being studied.
The criteria used to determine whether an individual can participate in a research study or whether an individual study can be included in a systematic review.
A study conducted over a long period of time, usually for the purpose of identifying long-term treatment effects.
A systematic method that takes data from several studies and integrates their results using statistical analysis.
A multicenter study takes place in various hospital or clinical settings, as opposed to a single location.
A statistical technique that allow investigators to examine more than two variables at the same time.
A study in which the participants are observed and certain outcomes are measured. There is nothing done to affect the outcome. In other words, no treatment is given.
A type of clinical trial in which researchers and study participants know which treatment is being given.
Patient-years or person-years
Patient-years refers to the total number of years that all of the study participants were followed in a particular study. For example, 10 patients participating in a study for 15 years is equivalent to 150 patient-years.
A study that focuses on a particular population of people who have one or more characteristics in common.
When considering an outcome variable in a study, also called the end point, the primary outcome is the most significant outcome (i.e., the result or outcome researchers are most focused on).
A trial which observes outcomes going forward, such as the development of a disease.
The treatment being tested is assigned to study participants in random fashion.
A study that looks into a patient's past history for exposures or risk factors that may explain their present circumstances.
Additional outcomes of a study that may explain additional effects of treatment, beyond the primary outcome.
A short summary of the completed research.
An evaluation of all prior research studies that meet inclusion criteria and looked at a specific issue.
Glossary of Terms. Effective Healthcare Program. Agency for Healthcare Research and Quality (AHRQ). Accessed 08/18/12.
Webster's New World Medical Dictionary, 3rd Edition. May 2008.