Cohortias – The Basic Components of Clinical Trials.

Each clinical trial has a written plan, or study protocol, that describes the goals of the study, how long the study will last, who can participate.

The Basic Components of Clinical Trials

The scientists and health care providers who manage clinical trials are usually called investigators. The people who join clinical trials are usually called participants but may also be called volunteers or study subjects. ALL clinical trials are voluntary. You never have to participate in a clinical trial unless you want to; this is a human right protected by international laws.

In 2002, the World Health Organization (WHO) released a Handbook for Good Clinical Research Practic (PDF). It is intended to help each country develop its own laws about clinical trials. The WHO’s handbook is based in part on the recommendations for good clinical practice developed by the International Conference on Harmonisation (ICH) in 1996. In the US, for example, the Food and Drug Administration (FDA), which approves drugs for public use, has adopted the ICH’s recommendations for clinical trials.

Study Protocol

Each clinical trial has a written plan, or study protocol, that describes the goals of the study, how long the study will last, who can participate (also called inclusion and exclusion criteria), and what tests and procedures will be conducted for each participant.

Inclusion and exclusion criteria

Inclusion and exclusion criteria are the guidelines for determining who can and cannot participate in a specific clinical trial.

Inclusion criteria are requirements that a person must meet to participate (such as HIV drug-naïve — never having taken HIV drugs — CD4 cell count, viral load, age, or many others).

Exclusion criteria are factors that prevent a person from participating, either for his or her safety or to make it easier to understand the study results. For example, people might be excluded for having liver problems, or if they have already taken a drug that is being studied.

For example, beginning in early 2020, the novel coronavirus (COVID-19) swept the globe, killing millions of people and infecting millions more. HIV community members advocated for HIV to be removed from the exclusion criteria for COVID-19 vaccine trials. As a result, people living with HIV were included in some of those studies, and the vaccines appear to be safe for people living with HIV to take.

clinical trials

Informed consent

Each participant in a clinical trial must sign a document called “informed consent.”

When you sign this document, it means that you understand the details of the study and you agree to participate.

You may want to take the document with you and talk about the study with your health care provider, family, or friends before you decide to participate. If your native language is not the language spoken by the people describing the study, you should ask if a translation is available.

It is important that you truly understand the study and what you will be asked to do. If you have any questions, be sure to ask the study staff. It is their job to make sure that you understand what you are agreeing to do when you sign this document.


You may be paid for travel expenses to and from the study site and for your time; this payment is sometimes called compensation. Childcare may also be provided. You can choose to leave (drop out of) a study at any time and for any reason.


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