Glossary of clinical trial terms 2018-05-27T12:55:03+00:00

Glossary of clinical trial terms


Adverse event is any adverse and untoward sign, symptom or disease (including deviations in laboratory test results) temporally associated with the use of a medicine or a medicinal product, which does not necessarily have a causal relation with the use of the medicinal product.

Assent is a child’s consent to participate in a clinical trial given by the child in addition to parental/guardian informed consent. If possible, this should be obtained in writing.

Audit is an examination conducted by the trial sponsor to inspect trial documentation, site and other resources in order to verify compliance with the regulatory requirements, standard operating procedures, good clinical practice and the protocol.


Blinding is a procedure used to ensure impartiality of the subjects, investigator and sponsor in a trial, meaning they are not aware of which treatment group a subject is assigned (e.g. which dose of the medicinal product he/she is receiving, whether he/she is receiving the investigational medicinal product, comparator or placebo, etc.). With respect to blinding, trials are divided into four groups:

  1. Open-label trial – both the investigator and the subject know which treatment group the subject is assigned to,
  2. Single blind trial – the subject does not know but the investigator does know which treatment group the subject is assigned to,
  3. Double blind trial – neither the subject nor the investigator know which treatment group the subject is assigned to,
  4. Triple blind trial – neither the subject nor the investigator or the persons analysing the data know which treatment group the subject is assigned to.


Clinical trial/study of a medicinal product is an investigation in human subjects conducted in accordance with a protocol, intended to discover or verify the pharmacokinetic and pharmacodynamic properties of the medicinal product and/or to discover any side effects or interactions of medicinal products and to determine their safety and/or efficacy.

Comparator is a previously registered medicinal product used in a clinical trial to compare the efficacy of the investigational medicinal product.

Compliance is a subject’s adherence to the instructions for regular taking of the investigational medicinal product and accepting other protocol requirements.


Efficacy of a medicinal product is its property to have a positive effect on a disease or condition.


Good Clinical Practice is a set of internationally recognized ethical and scientific procedures and requirements which have to be complied with while planning, conducting, recording and reporting on clinical trials.


Impartial witness is an independent person who witnesses a patient information procedure and signs an informed consent in the case that the subject cannot or is unable to read.

Independent Ethics Committee is an independent body constituted of healthcare professionals and members of nonmedical professions, who are responsible for the protection of the rights, safety and wellbeing of subjects included in clinical trials and who guarantee such protection, through, but not limited to, expressing their opinion on protocols, eligibility of investigators, suitability of the facility where the trial is to be conducted, on equipment and methods, and on documents to be used to inform subjects and obtain their consent on the basis of informed consent.

Informed Consent is a subject’s consent, in a written form, to participate in the clinical trial on the basis of properly documented information which refers to the nature and importance, consequences and risks of the trial, and is signed and dated by the subject and the investigator. If a subject is incapable of giving such consent or is underage, the consent is signed by his/her legal representative or guardian.

Inspection is an act by a regulatory authority undertaken to inspect trial documentation, site and other resources in order to verify compliance with the applicable legal instruments, good clinical practice and protocol.

Interaction of medicinal products is a change in the action and/or effect of a medicinal product when used with one or more medicinal products. Such change may have effect in changed efficacy or safety of the medicinal product.

Investigational medicinal product is a substance investigated in a clinical trial. An investigational medicinal product is investigated or used as a comparator in a clinical trial, including medicinal products with a marketing authorization when used in a new dose strength, or in a new delivery system, or are different in formulation or packaging, or are investigated for unapproved indications.

Investigator is a medical doctor or a person having appropriate professional qualifications for conducting clinical trials who is responsible for conducting a clinical trial at a trial site.

Investigator’s Brochure is a document presenting all results of the completed clinical and nonclinical trials for a medicinal product. This document provides information professionals need to know about medicinal product properties.


Marketing Authorization for the Finished Medicinal Product (Registration) is an approval granted by the Croatian Agency for Medicinal Products and Medical Devices which finalizes the procedure of determining the quality, efficacy and safety of a finished medicinal product and approves its marketing.
Medicinal product is any substance or a mixture of substances intended to treat or prevent diseases in humans.


Non-interventional (observational) trial of a medicinal product is a trial where the investigational medicinal product is prescribed in accordance with the marketing authorization and where certain data on subjects are collected. Patients are treated in accordance with common practice and prescription is made irrespective of the decision on whether to include a patient in the trial. No additional diagnostic or follow up procedures are conducted.


Placebo is an inactive substance or procedure, resembling an investigational medicinal product or treatment applied and having no therapeutic medicinal properties, which is used to determine the influence of a psychological reaction to the success of treatment (placebo effect).

Protocol is a document explaining the purpose and objectives of a trial, prescribing the conditions for a trial, schedule of tests and procedures to be performed, and specifying the data to be gathered to demonstrate that a medicinal product is safe and effective, as well as the method of statistical data processing.


Randomization is a procedure of assigning trial subjects to the treatment according to a defined parameter (e.g. with a higher or lower dose of the investigational medicinal product, comparator or placebo to be used) by random choice. Neither the subject nor the investigator can influence the subject’s assignment to a treatment group. This procedure reduces bias and ensures greater objectivity of data obtained in clinical trials.

Registration of a medicinal product – see Marketing Authorization for a Finished Medicinal product.


Screening is a procedure to determine whether a subject meets the inclusion (or exclusion) criteria.

Side effect is any adverse and unwanted reaction to an investigational medicinal product administered in any dose.

Sponsor is a legal or natural person responsible for the commencement and conduct of a clinical trial and/or paying the cost of a clinical trial. Sponsors may be academic communities, pharmaceutical companies, individual doctors, etc.

Subject is a person participating in a clinical trial entitled to be provided detailed information on the investigational medicinal product during the trial. The trial doctor should keep a subject informed of any new data which may affect his/her participation in the trial.


Trial see Clinical trial.

What are clinical trials?
Medicinal product development and phases of clinical trials
How are clinical trials conducted?
Possible benefits and risks of participation
Rights and protection of subjects
Glossary of clinical trial terms
Questions you may ask the trial doctor
Where can I get more information?