What Are the Exclusion and Inclusion Criteria to Participate in Clinical Trials?

Participating in clinical trials is one of the best ways that the average person can contribute to the advancement of medical knowledge in their community and the pioneering of new treatments for various conditions, including neurological ones.

However, not everyone is eligible to enroll in every clinical trial. For each clinical, depending on the research question, the clinicians are looking for patients with specific characteristics and health conditions to find the answer they seek.

Similarly, some patients that otherwise might be good candidates for a particular trial might be excluded because of one or more characteristics.

Here, let’s discuss inclusion and exclusion criteria, how they’re different, and examples of how researchers use them to screen and select trial participants.

What Are Inclusion Criteria in Clinical Trials?

Shortly put, inclusion criteria are the characteristics that a prospective participant must have in order to be accepted into a clinical trial.

Depending on the study design, inclusion criteria can be wide-ranging in nature but they often relate to the condition targeted for treatment:

“They typically identify a population in which it is expected that the effect of the drug can be shown. An obvious example is identifying patients with a specific mutation that is targeted by the treatment, where the drug is likely to be effective only in those patients with the disease who have the mutation.”

For more examples of common inclusion criteria, please see our later section on the topic.

What Are Exclusion Criteria in Clinical Trials?

Basically, exclusion criteria are the characteristics that would prevent a prospective participant from gaining acceptance into a clinical trial.

The purpose of exclusion is to rule out confounding variables that would muddy the analytical waters and hinder the clinicians from accurately assessing the effectiveness of the treatment or drug under study:

“Exclusion criteria specify characteristics that disqualify patients from participation and often include factors such as comorbidities or concomitant treatment or factors that could mask the effect of the intervention.”

For more examples of common exclusion criteria, please see our next section on the topic.

What Characteristics Are Typically Used as Inclusion and Exclusion Criteria?

The list of potential inclusion and exclusion criteria is long, and they vary widely from study to study. Here are some of the most common factors on which inclusion and exclusion hinge:

  • Smoker/nonsmoker
  • Ethnicity
  • Race
  • Weight
  • Underlying medical conditions
  • Age
  • Sex
  • Diet
  • Medications
  • Psychosocial or emotional conditions
  • Logistical challenges limiting access to patients/patients’ mobility/language barriers
  • Physical activity levels
  • Type and stage of disease
  • Treatment history

What Considerations Do Clinicians Make When Weighing Inclusion and Exclusion Criteria?

We all know the world is an imperfect place. Ideally, researchers would have a pool of perfect participants to select from, with all of the characteristics on their inclusion list and none on their exclusion list.

However, because the perfect world doesn’t exist, clinicians have tough choices to make in terms of who to include and who to reject for clinical trial participation.

Accordingly, here are some considerations when developing inclusion and exclusion criteria:

  • If the inclusion criteria are too narrow or the exclusion criteria too numerous, the pool of available candidates might shrink too much and render the study infeasible.
  • If the same problem with narrow inclusion and vast exclusion criteria exists, the study results might not be applicable to the wider population.
  • If the inclusion criteria are too large, the results might not effectively address the specific research question (for example, by not properly focusing on the target treatment group).
  • Because clinical trials occur in the real world with all of its logistical challenges, researchers often need to accommodate these difficulties when deciding who to accept or reject.
  • The researchers often create a hierarchy of criteria – from essential at the top of the pyramid to trivial at the bottom. Accordingly, when necessary, they then begin eliminating trivial criteria.

What Are the Benefits to Clinical Trial Participants Who Meet All the Inclusion Criteria?

One of the most common (and basic) questions that individuals considering participation in a clinical trial ask is: why should I join?

After all, in many instances, the study in question is investigating novel new therapeutic approaches that don’t necessarily have a proven track record of success and may pose some health risks – that’s what clinical trials exist to investigate.

So, what’s in it for participants? Here are a few reasons that you might want to consider enrolling in a clinical trial:

  • Access to new treatments before they become available to the general population
  • Ongoing health monitoring and healthcare from industry-leading experts throughout the trial
  • Helping to advance medical knowledge and develop transformative, often life-saving treatments
  • Compensation for time and travel
  • Free medications/treatments

What Is Informed Consent in Inclusion Criteria?

One of the most common inclusion criteria is called “informed consent.”

Obtaining informed consent from the patient, contrary to popular perception, is much more than simply “signing on the dotted line.” According to FDA guidelines, informed consent requires:

  • “providing a potential subject with adequate information to allow for an informed decision about participation in the clinical investigation”
  • “facilitating the potential subject’s comprehension of the information”
  • “providing adequate opportunity for the potential subject to ask questions and to consider whether to participate”
  • “obtaining the potential subject’s voluntary agreement to participate”
  • “continuing to provide information as the clinical investigation progresses or as the subject or situation requires”

Informed consent is a cornerstone of American medical ethics. Learn more about the patient’s right to informed consent.

Can Minors Give Informed Consent?

Children are generally regarded as unable to provide informed consent. Therefore, parents are generally responsible for giving informed consent on behalf of their children in the context of medical treatment, including for enrollment in clinical trials.  

Contact Northwest Florida Clinical Research Group to Enroll in a Study or Learn More

Northwest Florida Clinical Research Group (NWFLCRG) is one of the region’s leading neurological research groups. To learn more about participating in a clinical trial or how to enroll in one of our ongoing studies, check out our Clinical Trials page. Of course,  we’re always available to answer any questions related to the exciting and rapidly developing field of neurological research. Contact Northwest Florida Clinical Research Group to learn more about the work we do.

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