Glossary of terms

Bias: 

In research, the term ‘bias’ is used when a particular design or analysis is likely to favour a particular outcome. In a clinical trial, if one treatment is always given to participants who have a more severe form of a disease, then this treatment will appear worse than others. Bias can also happen if a researcher knows about the treatment a participant is receiving, and this interferes with the researcher’s ability to be impartial. It is important to avoid bias in health research, as it can distort the results and could lead to unsafe or ineffective treatments being licensed for use, or useful treatments being overlooked. Researchers try to avoid bias by using randomisation and by ‘blinding’ those assessing the results of treatments, which may be both the patient and the doctor

Blind / Blinding: 

Blinding means that study participants and/or the researchers assessing the effects of treatment do not know which treatment each person has received. This helps to prevent bias. A study is considered double-blind when neither the participant nor the researchers are aware which participants are in the control group and which are in the active treatment group. This is to avoid aims and expectations that may influence the outcome. This is considered the gold standard of studies as it is tightly controlled and external variables are significantly reduced or balanced between the control and treatment group.

Clinical (or healthcare research) study:

A research study involving human volunteers (also called participants) that is intended to add to medical knowledge. There are two types of clinical studies: interventional studies (also called clinical trials) and observational studies.

Clinical trial:

Another name for an interventional study.

Interventional study:

A type of clinical study in which participants are assigned to groups that receive one or more intervention/treatment (or no intervention) so that researchers can evaluate the effects of the interventions on biomedical or health-related outcomes. The assignments are determined by the study's protocol. Participants may receive diagnostic, therapeutic, or other types of interventions.

Observational study:

An observational study investigates health outcomes amongst groups of people in the course of their everyday life. Participants may receive diagnostic, therapeutic, or other types of interventions but this is part of their regular medical care (not assigned by the research study /investigator).

Open-label extension (OLE):

An Open Label Extension, or OLE, is a phase of a study that occurs after the randomised (blinded) portion of the trial is completed. All eligible participants receive the active form of the drug.

Phase:

Categories for describing the clinical trial of a drug based on the study's characteristics, such as the objective and number of participants. There are four phases:
  • Phase I trials test an experimental drug in a small group of people to evaluate safety, identify side effects and determine safe dosages. 
  • Phase II trials involve larger groups of people than Phase I and they are designed to assess whether an experimental treatment is safe and whether it works. This phase can last several years. 
  • Phase III trials are usually large studies comparing the experimental drug to a placebo or standard treatment, to evaluate whether the drug works and collect information to allow it to be used safely. 
  • Phase IV trials are performed once a drug has reached the market, to provide additional information about the best use of the drug.

Placebo / placebo group:

A placebo is an inactive substance or treatment that looks the same as an active drug or the intervention being studied. Placebo is given to the control group to assess the difference between this group and the intervention group, to be confident that any differences between the groups can be attributed to the active drug or intervention.

Placebo effect:

The placebo effect is a physical or emotional change occurring after a substance is taken and not as a result of the specific properties of a drug. The change may be beneficial and reflects the expectation of the participant or the administrator.

Randomised controlled trial / randomly assigned:

Randomised controlled trials  are interventional studies that study the cause-effect relationship of a drug being studied. Participants are randomly assigned to a group that is either a control group or the intervention group. Random assignment is to minimise bias and balance individual characteristics so any differences between the groups are attributed to the intervention.The study protocol outlines the ratio of people that will be assigned to the intervention group or control group, for example "a 3:2 ratio of study drug to placebo" means that for every 5 participants enrolled, 3 people will be randomly assigned to receive the intervention and 2 people will be randomly assigned to the control group.