Clinical Trial Terminology, Grouped by Workflow and Stamped to ICH E6(R3) (2025)

At a glance

• This is a working reference, not an A-to-Z dump: terms are grouped by the workflow where they actually bite (consent, safety, data, conduct, oversight), and every definition is stamped to its current source so you can check your SOP language against ICH E6(R3) (2025).
• ICH E6(R3) was adopted on 06 January 2025 and carries a rebuilt master glossary; the safety chain (AE, SAE, SUSAR, expectedness) still routes through ICH E2A, and US investigator/IND obligations live in 21 CFR Part 312.
• “Serious” and “severe” are not the same word: seriousness drives reporting obligations under ICH E2A, severity describes intensity. Confusing them generates findings.
• “Reconciliation” has two distinct GCP senses, and they belong to different teams: SAE database reconciliation (safety) and data/CRF reconciliation (data management).
• The confused-pairs table below covers the look-alikes inspectors see most: AE vs SAE vs SUSAR, deviation vs important deviation, source vs essential records, monitoring vs audit vs inspection, sponsor vs CRO vs investigator.
• Definitions describe what the regulations require; meeting them is the sponsor’s and investigator’s responsibility, not a property any tool or template confers.

How to use this reference

Flat glossaries answer “what does this word mean” but not “when does it matter and which definition is current.” This reference fixes both. Terms are grouped by the stage of the trial where you reach for them, and each carries the regulation it comes from plus its version, so you can tell at a glance whether your site or SOP wording matches the 2025 standard.

Three sources do the work here. ICH E6(R3) Good Clinical Practice supplies the GCP master glossary and the rules for deviations, monitoring, audit, and data handling. ICH E2A supplies the clinical-safety vocabulary (adverse event, serious, unexpected, the expedited-reporting standard). For trials run under a US IND, 21 CFR Part 312 supplies the statutory definitions and the investigator and sponsor obligations. Where two of these speak to the same point, this reference shows you both rather than blending them.

What ICH E6(R3) changed (2025): read the glossary, not just the body

ICH E6(R3) was adopted on 06 January 2025 as the current Step 4 version, superseding the E6(R2) wording. The most practical change for anyone reaching for a glossary is structural: E6(R3) carries a consolidated master glossary that defines the core GCP vocabulary in one place, and it leans on terminology that reflects modern, media-neutral, risk-based trial conduct.

A few wording shifts are worth flagging because they show up in SOPs. E6(R3) uses “trial participant” (with “participant” used interchangeably) rather than the older “subject.” It defines “Essential Records” as the documents and data, in any format, associated with a trial that allow evaluation of the methods used and verification that the trial was conducted in accordance with GCP and applicable regulatory requirements. It defines “Source Records” as original documents or data, or certified copies, irrespective of media, explicitly including participant-entered data such as ePROs and data from wearables and sensors. And it frames “Data Integrity” around data being attributable, legible, contemporaneous, original, accurate, complete, secure and reliable such that data are fit for purpose, which is the ALCOA-plus idea written into the glossary itself.

Caution on currency: US terminology under 21 CFR Part 312 still uses “subject” as the defined term (a human who participates in an investigation, as recipient or control). So a protocol can correctly say “participant” in its GCP framing and “subject” where it cites Part 312. That is alignment of two current sources, not an error to scrub.

Consent and participant terms

• Informed consent — Under ICH E6(R3), informed consent is the process by which a participant or their legally acceptable representative voluntarily confirms willingness to participate after being informed and given the opportunity to discuss all relevant aspects; it is documented by a written, signed and dated consent form. ICH E6(R3) requires that freely given informed consent be obtained and documented from every participant prior to participation. Under 21 CFR 312.60, the investigator is responsible for obtaining the informed consent of each human subject in accordance with Part 50.
• Assent — ICH E6(R3) defines assent as the affirmative agreement of a minor to participate; the glossary is explicit that the absence of expressed agreement or disagreement should not be interpreted as assent. Practically: silence is not assent.
• Legally acceptable representative — Per ICH E6(R3), an individual or body authorised under applicable law to consent on behalf of a prospective participant who cannot consent themselves.
• IRB / IEC — ICH E6(R3) defines the Institutional Review Board / Independent Ethics Committee as an independent body responsible for protecting the rights, safety and well-being of participants, including by reviewing and approving the protocol and the consent process. Under 21 CFR 312.66, the investigator must assure that an IRB meeting Part 56 requirements is responsible for initial and continuing review.

Safety terms, and the AE / SAE / SUSAR chain

This is where most terminology findings originate, so treat the chain as a sequence, not a synonym list.

• Adverse event (AE) — ICH E2A defines an adverse event as any untoward medical occurrence in a patient or clinical investigation subject administered a pharmaceutical product, which does not necessarily have a causal relationship with the treatment. ICH E6(R3) carries the same concept in its glossary.
• Adverse drug reaction (ADR) — ICH E2A treats a pre-approval ADR as a response where a causal relationship between the medicinal product and the event is at least a reasonable possibility, meaning the relationship cannot be ruled out. The dividing line between an AE and an ADR is causality.
• Serious adverse event (SAE) — Under ICH E2A, an event is serious if at any dose it results in death, is life-threatening, requires inpatient hospitalisation or prolongation of existing hospitalisation, results in persistent or significant disability/incapacity, or is a congenital anomaly/birth defect. ICH E6(R3) reproduces these same seriousness criteria in its glossary. Note the inclusion of important medical events that may require intervention to prevent one of those outcomes.
• Serious is not severe. ICH E2A is explicit that “serious” and “severe” are not synonymous: severity describes the intensity of an event, while seriousness is based on patient or event outcome, and seriousness (not severity) serves as the guide for defining regulatory reporting obligations. A “severe headache” may be entirely non-serious.
• Unexpected — ICH E2A defines an unexpected adverse reaction as one whose nature or severity is not consistent with the applicable product information, such as the Investigator’s Brochure. Expectedness is judged against the source document, not against pharmacological plausibility.
• SUSAR — A Suspected Unexpected Serious Adverse Reaction is, per ICH E6(R3), an adverse reaction that meets three criteria at once: suspected, unexpected and serious. Drop any one criterion and it is not a SUSAR.

On reporting timeframes, two current sources speak and they do not say the same thing, so do not flatten them. ICH E2A sets the expedited-reporting standard for the sponsor’s notification to regulators: fatal or life-threatening unexpected ADRs as soon as possible but no later than 7 calendar days after first knowledge, with a complete report within 8 additional days; all other serious, unexpected ADRs no later than 15 calendar days. 21 CFR 312.64(b) imposes a different obligation in a different direction: the investigator must immediately report to the sponsor any serious adverse event, whether or not considered drug related. And 21 CFR 312.32 sets the sponsor’s IND safety report clock to FDA at no later than 15 calendar days after the sponsor determines the information qualifies. These are complementary clocks, not duplicates: investigator-to-sponsor (immediate, Part 312), and sponsor-to-regulator (7/8 or 15 day under E2A; 15 day under Part 312). Map your SOP to the right arrow.

This is also reconciliation sense #1. ICH E6(R3) lists “SAE reconciliation” among the records documenting data finalisation, the cross-check that the clinical database and the safety (pharmacovigilance) database agree on which SAEs exist and how they are coded.

Data and document terms

• Source records — ICH E6(R3) defines source records as original documents or data, or certified copies, irrespective of media, including participant medical records, ePROs, and data from automated instruments such as wearables and sensors.
• Essential records — ICH E6(R3) defines essential records as the documents and data, in any format, that allow evaluation of the trial and verification that it was conducted in accordance with GCP and applicable regulatory requirements. Source records prove what happened to a participant; essential records collectively prove the trial was run properly.
• Case report form (CRF) — Per ICH E6(R3), a data acquisition tool designed to record protocol-required information reported by the investigator to the sponsor on each participant. Under 21 CFR 312.62, the investigator must prepare and maintain adequate and accurate case histories, which include the case report forms and supporting data such as signed and dated consent forms and medical records.
• Certified copy — ICH E6(R3) defines a certified copy as a copy verified, by dated signature or a validated process, to have the same information as the original, including relevant metadata.
• Data integrity (ALCOA framing) — ICH E6(R3) defines data integrity by the degree to which data are attributable, legible, contemporaneous, original, accurate, complete, secure and reliable such that they are fit for purpose.

This is reconciliation sense #2. ICH E6(R3) describes activities to finalise data sets prior to analysis that may include reconciliation of entered data and data sets or reconciliation of relevant databases, alongside rectification of data errors and addressing the impact of noncompliance issues including protocol deviations. That is data/CRF reconciliation, a data-management activity. It is not the same task as SAE reconciliation above, even though both use the word.

Conduct and oversight terms

• Protocol deviation — ICH E6(R3) requires the investigator to document all protocol deviations, review them, and for those deemed important, explain the deviation and implement measures to prevent recurrence. The guideline contemplates that the investigator should follow the protocol and deviate only where necessary to eliminate an immediate hazard to participants, informing the sponsor promptly when that happens.
• Important protocol deviation — ICH E6(R3) has the sponsor define trial-specific criteria for classifying deviations as important, and defines important protocol deviations as a subset that may significantly impact the completeness, accuracy or reliability of the trial data, or significantly affect a participant’s rights, safety or well-being. (The guideline does not define a separate term “protocol violation”; in practice teams use “violation” loosely, but the E6(R3) construct is deviation vs important deviation.)
• Monitoring — ICH E6(R3) defines monitoring as overseeing the progress of a trial and ensuring it is conducted, recorded and reported in accordance with the protocol, SOPs, GCP and applicable regulatory requirements. It is a sponsor activity.
• Audit — ICH E6(R3) defines an audit as a systematic and independent examination of trial-related activities and records, performed by the sponsor, service provider (including CRO) or institution, to determine whether activities were conducted and data recorded, analysed and reported per the protocol, SOPs, GCP and applicable regulatory requirements.
• Inspection — ICH E6(R3) defines inspection as the act by a regulatory authority of conducting an official review of documents, facilities, records and other resources related to the trial. Monitoring is routine and sponsor-run; audit is independent and sponsor- or institution-run; inspection is the regulator’s.
• Sponsor — ICH E6(R3) defines the sponsor as the individual, company, institution or organisation that takes responsibility for the initiation, management and arrangement of financing of a trial. 21 CFR 312.3 defines the sponsor as the person who takes responsibility for and initiates a clinical investigation and who does not actually conduct it unless they are a sponsor-investigator.
• CRO — 21 CFR 312.3 defines a contract research organization as a person that assumes, as an independent contractor with the sponsor, one or more of the sponsor’s obligations. In ICH E6(R3) terms the CRO is a service provider; either way, ICH E6(R3) is clear that responsibility for the conduct of the trial, including data quality and integrity, resides with the sponsor even where activities are transferred.
• Investigator and sub-investigator — 21 CFR 312.3 defines the investigator as the individual who actually conducts a clinical investigation, with the responsible leader of a team being the investigator and other team members being subinvestigators. 21 CFR 312.60 makes the investigator responsible for conducting the study per the signed statement and investigational plan, protecting subjects, and controlling the investigational drug.
• Sponsor-investigator — Both ICH E6(R3) and 21 CFR 312.3 define a sponsor-investigator as an individual who both initiates and conducts the trial; the obligations of a sponsor-investigator include both those of a sponsor and those of an investigator.
• IND in effect — 21 CFR 312.20 requires a sponsor to submit an IND when intending to conduct a clinical investigation subject to 312.2(a), and prohibits beginning that investigation until an IND is in effect. “Investigational” is a regulatory status, not a description of the molecule.

Confused-pairs quick table

Term A	Term B	One-line distinction	Why it matters
Adverse event (AE)	Serious adverse event (SAE)	An AE is any untoward occurrence; an SAE meets ICH E2A seriousness criteria (death, life-threatening, hospitalisation, disability, congenital anomaly)	Seriousness, not severity, sets the reporting clock
SAE	SUSAR	A SUSAR is an adverse reaction that is suspected, unexpected and serious (all three, per ICH E6(R3))	Only the SUSAR/serious-unexpected-ADR subset triggers expedited reporting under ICH E2A
Serious	Severe	Serious is an outcome category; severe is intensity (ICH E2A)	A “severe” but non-serious event is mislabeled if reported as serious
Protocol deviation	Important protocol deviation	Important deviations are the subset that materially affect data reliability or participant rights/safety (ICH E6(R3) 3.9.3)	Only important deviations drive remediation and recurrence prevention
Source records	Essential records	Source proves what happened to a participant; essential records prove the trial was run properly (ICH E6(R3))	Misfiling one as the other creates TMF and reconstruction gaps
Monitoring	Audit	Audit	Inspection
Sponsor	CRO	Investigator	Sponsor takes responsibility and initiates; CRO is an independent contractor assuming sponsor obligations; investigator conducts (ICH E6(R3) / 21 CFR 312.3)
Reconciliation (safety)	Reconciliation (data)	SAE database vs clinical database cross-check, vs data/CRF reconciliation of entered data and data sets (ICH E6(R3))	Different owners, different timing, different evidence

Where teams get it wrong

A handful of confusions generate most terminology findings:

• Treating “serious” as a synonym for “severe.” ICH E2A draws the line explicitly, and using “severe” to mean “serious” in SAE narratives is a recurring inspection comment.
• Reporting too much, or the wrong direction. Investigators owe the sponsor an immediate report of any SAE under 21 CFR 312.64(b); the sponsor owes regulators an expedited report only for the serious-unexpected subset under ICH E2A and a 15-day IND safety report under 21 CFR 312.32. Collapsing these into one rule causes both over- and under-reporting.
• Calling every deviation “important.” ICH E6(R3) reserves “important” for the subset affecting data reliability or participant rights and safety; over-flagging dilutes the signal CAPA depends on.
• Using one word “reconciliation” for two jobs. SAE reconciliation (safety vs clinical database) and data/CRF reconciliation (entered data vs data sets) are different activities owned by different teams in ICH E6(R3); a SOP that conflates them leaves a gap at database lock.
• Assuming silence is assent. ICH E6(R3) states the absence of expressed agreement or disagreement is not assent.

Downloadable reference

The two tables above (the workflow-grouped definitions with their current source, and the confused-pairs disambiguation) are the printable deliverable: keep them at the bench or in the eTMF as a one-page check that your site and SOP language matches ICH E6(R3) (2025), with the E2A safety chain and 21 CFR Part 312 obligations called out where they apply. For related detail, see the sibling references on protocol deviations, informed consent, SAE/SUSAR safety reporting, and essential documents and the TMF.

A closing reminder in the house style: these definitions describe what the regulations require. Matching your terminology to them is necessary, but it is the sponsor’s and investigator’s ongoing responsibility to conduct the trial in compliance; getting the words right does not by itself make a trial compliant.

Sources

• ICH E6(R3) Good Clinical Practice, version r3 (adopted 06 January 2025) — https://www.ich.org/page/efficacy-guidelines
• ICH E2A Clinical Safety Data Management: Definitions and Standards for Expedited Reporting, version r1 (Step 4, 27 October 1994) — https://database.ich.org/sites/default/files/E2A_Guideline.pdf
• 21 CFR Part 312 Investigational New Drug Application, version 2026-04 (eCFR, up to date as of 4/14/2026)