Definitions of Key Terms Related to Research

Along their PH journeys, patients may be presented with the opportunity to participate in PH research, which can present a whole new set of terminology to learn. The following definitions have been designed to help patients and their loved ones navigate the research language as they consider participating in clinical studies or read through the findings of exciting new research. Special thanks to Arjun Pandey who has volunteered his time and research skills to help us develop this resource.

Research Phases

Pre-Clinical Studies
Before a new treatment is tested on humans, initial research is conducted to determine potential safety concerns. Pre-clinical studies are typically done in a lab and involve testing on cells, tissue samples, and/or animals.  

Clinical Studies
Once pre-clinical studies have shown that a treatment is not dangerous, it is tested on humans in clinical studies (also know as clinical trials). Clinical studies allow researchers to determine the treatment’s efficacy and potential for use in the general population. Clinical studies are accomplished over many years in multiple phases:

Phase I
Goal:
To determine the treatment’s safety when used on humans.
Participants:
Between 20-80 typically healthy participants.
Duration:
Several months.

Phase II
Goal:
To measure the treatment’s efficacy as a therapeutic option for a given condition and to continue to evaluate its safety.
Participants:
Generally between 100-300 people affected by the targeted condition Duration: Up to two years.

Phase III
Goal:
To evaluate the treatment’s efficacy compared to standard of care (available existing treatments) and/or a placebo-control (inactive substance that looks identical to a drug but has no effect on the body).
Participants:
May include up to thousands of people affected by the targeted condition.
Duration:
Up to four years.

Phase IV
Goal:
To measure the treatment’s real-world efficacy, determine its optimal use, and evaluate its safety in larger populations.
Participants:
Larger group of people affected by the targeted condition.
Duration:
Long-term research undertaken after a treatment has been available for sale.

Terminology

Informed Consent: A process whereby participants are informed of the potential risks and benefits of participation in a trial prior to giving their consent to participate.

Placebo: an inactive substance that looks identical to the drug being studied but has no effect on the body.

Standard of care: Standard of care is a term used in medical studies that refers to treatments currently available for prescription as opposed to new treatments being researched. Studies typically compare novel treatments against the standard of care in order to determine the efficacy of a new drug under study in comparison to existing treatments.

Types of Studies

Randomized/Non-Randomized

Randomized: In this type of study, participants are randomly assigned to a study group. In this trial design, chance alone determines which group a participant gets placed in, which eliminates bias.

Non-randomized: In this type of study, participants are assigned to a study group based on specific criteria. The main types of studies falling under this category are:

  1. Cohort studies, which follow a cohort (group) of participants prospectively (from a point in time onwards) or retrospectively (examining data that has already been collected).
  2. Case-control studies, which compare data collected from participants who have a given disease (cases) to that of participants who do not have the disease (controls) retrospectively (examining data that has already been collected). This type of research is useful in rare diseases as it allows researchers to determine which demographic elements and risk factors are most strongly associated to the disease.
  3. Cross-sectional studies, which provide information about the differences between study groups at a specific point in time (rather than longitudinal studies that examine these relationships over longer time periods).

Interventional/Non-Interventional

Interventional: This type of study involves an intervention in participants’ care and/or routine. Researchers may use this type of study to test a new treatment, a new diagnostic technique, or existing treatments.

Non-interventional or observational: In this type of study, researchers observe participants without intervening in their care and/or routine. These studies can be conducted prospectively (from a point going forward) or retrospectively (examining data that has already been collected).

Single-Group/Multi-Group

Single-group study: In this type of study, all participants are prescribed a treatment and the effects of that treatment are subsequently studied. These kinds of studies do not involve control groups in which participants may be given a placebo.

Study arms: The term study arms refers to the group or sub-group to which a participant belongs in a clinical trial. The arms of a study are determined before the research begins. For example, one arm of the study may be receiving a placebo-control, another may be receiving a low dose of the studied drug, and a final group may be receiving a higher dose of the drug.

Placebo-controlled: In this type of study, a group of participants is given an inactive substance that looks identical to the drug being studied but has no effect on the body (placebo). The “placebo effect” is known as a phenomena in which an impact is noticed on participants who have been given a placebo and told it may improve their condition. To reduce bias in placebo-controlled studies, participants are often not told whether they are given the placebo-control or the drug under study.

Parallel/Crossover Assignments

Parallel assignment: This term refers to a method of conducting a study in which participants are assigned to a group and remain in that same group for the entire duration of the study (i.e. participants are assigned to either the control group or the intervention group for the study). Parallel studies rely on randomization to ensure that there is no bias in the creation of the groups.

Crossover assignment: Crossover studies are studies in which participants are assigned to a study arm for a specific period of time and, after a given period of time, are then assigned to another arm of the study. As an example, a participant may be assigned to a placebo-control group for 6 months and, after a delay, may be assigned to the intervention group for 6 months or vice versa. In this study design, every participant will be given the studied drug at one point of the trial.

Single-Blinded/Double-Blinded

Single-blinded: In this type of study, information about which group participants have been assigned to is withheld from either the researchers or the participants. This technique is used to reduce bias in either researchers or participants.

Double-blinded: In this type of study, information about which group participants have been assigned to is withheld from both the researchers or the participants. This technique is used to reduce bias in both researchers and participants. For example, a double-blinded randomized placebo-controlled trial is one in which participants are randomly assigned to either the drug-intervention group or the placebo-control group without being told which one. Similarly, the researchers are not told which participants have been assigned to which group. This type of study is considered the gold standard of clinical research.

Sources:

https://clinicaltrials.gov/ct2/about-studies/glossary

http://www.takeda.us/research_development/pdf/clinicaltrialsglossary.pdf

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