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Clinical Trial Terminology and Glossary

Clinical trials are robust scientific experiments that test a new medical treatment on humans to prove their safety and efficacy.

There are several clinical research terms that may be new to you. This section provides definitions for words and terms you may need to know.

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Eligibility Criteria

A list of criteria guiding enrollment of participants into a clinical research study. The criteria describe both inclusive and exclusive factors (e.g., inclusion criterion - participants must be aged between 55 and 85 years old; exclusion criterion – must not take drug X 3 months before the study).


A procedure such as a drug, dietary supplements, gene transfer, vaccine, behavior, or device modification that is performed for clinical research purposes.


A document that indicates the objective/s, design, methodology, statistical considerations, and organization of a clinical trial.

Age or Age Group

A type of eligibility criteria that indicates the age a person must be to participate in a clinical study. This may be indicated by a specific age or the following age groups:
The age groups are:

  • Child (birth-17)
  • Adult (18-64)
  • Older Adult (65+)

Adverse Event

Any untoward or unfavorable medical occurrence to a clinical research study participant, such as any abnormal sign (e.g., abnormal physical examination or laboratory finding), symptom, or disease, temporally related to the participant's involvement in the research study, whether or not considered causally related to participation in the research.

Clinical Study

A research study conducted on human volunteers to answer specific health questions. Interventional studies determine whether an experimental treatment or new ways of using known therapies are within the safe dosage range and are effective under controlled environments.

Principal Investigator (PI)

Also known as the medical researcher, the principal investigator is responsible for the scientific and technical direction of the entire clinical study.

Observational Study

A type of clinical study where participants are identified as belonging to study groups and are assessed for biomedical or health outcomes. Participants may receive diagnostic, therapeutic, or other types of interventions, but the investigator does not assign participants to specific interventions/treatments.

A patient registry is a type of observational study.

Quality Control (QC) Review

The internal operational techniques and activities executed within the quality assurance system to verify that the requirements for quality of clinical trial-related activities have been fulfilled (e.g., data and form checks, monitoring by the clinical research team, routine reports, correction actions, etc.).

Interventional Study (Clinical Trial)

Also called a clinical trial, a type of clinical study in which participants receive one or more interventions according to the protocol and group they are assigned to so researchers can evaluate the effects of the intervention on a health condition.


A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Currently Enrolling Studies

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The process of submitting and updating summary information about a clinical study and its protocol, from its beginning to end to a structured, public web-based study registry that is accessible to the public.


The point of a participant's entry into the clinical trial after informed consent has been obtained. This term may also be used to define the number of participants who joined a clinical trial.

Eligibility Criteria

These are the requirements that people who want to participate in a clinical study must meet. The eligibility criteria include inclusion criteria and exclusion criteria and are defined in the study protocol.


Categories, as defined by the Food and Drug Administration (FDA), for describing the clinical trial of a drug based on the clinical study's characteristics, such as the objective and number of participants.


Usually a pharmaceutical, drug, or medical device company that wishes to investigate the effectiveness of a new product and financially supports the investigation.

Cross-Over Assignment

A type of intervention model describing a clinical trial in which groups of trial participants receive two or more interventions in a specific order.

For example, a two-by-two cross-over assignment involves two groups of participants. One group receives drug A during the initial phase of the clinical trial, followed by drug B during a later phase. The other group receives drug B during the initial phase, followed by drug A. So, during the clinical trial, participants "cross over" to the other drug. All participants receive drug A and drug B at some point during the clinical trial but in a different order, depending on the group to which they are assigned.


An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.

Human Subjects Protection Review Board

A group of people who review, approve, and monitor the clinical study protocol. Their role is to protect the rights and welfare of people participating in a study (referred to as human subjects), by providing oversight such as reviewing the informed consent form. The group typically includes people with varying backgrounds, including a community member, to make sure that clinical research activities conducted by an organization are completely and adequately reviewed. Also called an institutional review board, IRB, or an ethics committee.

Informed Consent

Informed consent is used by researchers to explain the clinical trial to potential volunteers. It aims to protect the participants. It is used when someone who is interested in participating first asks about the study, and it continues all throughout the study until the study ends. The research team will assess the details of the clinical trial with the potential participant and will answer any concerns. This information is also written in a document form, also known as the informed consent form, which is designed to be clear and easy to understand. If a person decides to participate in a clinical trial, they will sign the informed consent form to acknowledge their understanding of the details of the clinical trial and consent to participate. An informed consent form is not a contract; the trial participant can withdraw from the clinical trial at any time and for any reason.

Intervention Model

The general design of the strategy for assigning interventions to participants in clinical studies. Types of intervention models include the following: single group assignment, parallel assignment, cross-over assignment, and factorial assignment.

Early Phase 1 (Formerly Listed as Phase 0)

A phase of research used to describe exploratory clinical trials conducted prior to traditional phase 1 clinical trials to examine how or whether a drug affects the body. They involve limited human exposure to the drug and have no therapeutic or diagnostic goals (for example, screening studies and microdose studies).

Phase 1

A phase of research that describes clinical trials focusing on drug safety. They are usually conducted with healthy human volunteers, and the goal is to determine the drug's most frequent and serious adverse events and, often, how the drug is broken down and excreted by the body. These clinical trials usually involve a small number of participants.

Phase 2

A research phase to describe clinical trials that gather preliminary data on whether a drug works in people with a certain condition/disease (that is, the drug's effectiveness).

For example, study participants receiving the drug may be compared to similar participants receiving a different treatment, usually an inactive substance (called a placebo) or a different drug. Safety continues to be evaluated, and short-term adverse events are studied.

Phase 3

A phase of research to describe clinical trials that gather more information about a drug's safety and effectiveness by studying several different populations and dosages and by using the drug in combination with other drugs. These clinical studies typically involve more participants.

Phase 4

A phase of research to describe clinical trials occurring after a drug has undergone FDA approval for marketing. They include postmarket requirements and commitment studies that are required of or agreed to by the study sponsor. These clinical trials conduct data collection about a drug's safety, efficacy, or optimal use.

Currently Enrolling Studies

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Reporting Group

A grouping of study participants in a clinical study used for summarizing the data collected during the study. This grouping may be the same as or different from a study arm or group.


Placebos are inactive substances. In a clinical trial, a placebo is made to look like the investigational treatment. It is sometimes used to compare against the actual investigational treatment to evaluate effectiveness.

Control Group

A control group refers to a group of clinical trial participants who do not receive the drug or treatment being studied in the trial but instead receive a standard of care or a placebo.

US Department of Health and Human Services

The US Department of Health and Human Services is a government agency that provides clarification and guidance on the whole clinical trial process, develops educational programs and materials, and provides advice on ethical and regulatory issues.

Office for Human Research Protections

The Office for Human Research Protections (OHRP) establishes criteria for compliance with the Health and Human Services policy for the protection of human subjects in research conducted or supported by several federal agencies. Institutions involved in human subject research must sign an Assurance indicating their agreement to comply with the OHRP's regulations to receive federal research support.

Food and Drug Administration (FDA)

The Food and Drug Administration is responsible for regulating clinical research submitted in marketing applications for food, drugs, cosmetics, and medical devices in the US.

Institutional Review Board (IRB)

An Institutional Review Board (IRB) must approve every clinical trial in the United States at each study site. The IRB consists of doctors, scientists, and laypeople, like yourself, who are dedicated to ensuring that the study participants aren't exposed to unnecessary risks. The people at the IRB regularly review the study and its results. They ensure that participants' risks (or potential harms) are as low as possible.

Research Study Participants in Tampa Bay

Ongoing Clinical Research Studies in Tampa

We will answer your questions and keep you informed. We want you to successfully enroll in the most appropriate study based on your needs so you can have the best possible results.

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At Santos Research Center, Corp., we have completed over 400 clinical trials. We utilize efficient and reliable systems to plan and manage quality medical research studies.

For more information about our ongoing clinical research, you may visit us at www.santosresearch.com.

If you are interested in participating in our paid clinical trials, contact us at (813) 249-9100.

Santos Research Center, Corp. is a research facility conducting paid clinical trials, in partnership with major pharmaceutical companies & CROs. We work with patients from across the Tampa Bay area.

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