Examples
Worked examples
- Is an instance
A co-investigator physician at a trial site is delegated authority to obtain informed consent and perform protocol-specified physical exams; the PI lists them by name on the FDA Form 1572 and records their specific delegated duties, effective dates, and CV/training documentation on the site's Delegation of Authority log.
- Is an instance
A research fellow is authorized on the delegation log to review and grade adverse events under the PI's supervision, but is not authorized to make final eligibility determinations -- that duty remains reserved to the PI or a specifically delegated sub-investigator with the requisite clinical judgment authority.
Counter-examples
Looks similar, but isn't
- Not an instance
A study coordinator who schedules visits, enters case report form data, and handles participant logistics is not a sub-investigator: those duties are administrative/data-entry rather than the 'critical trial-related procedures' or clinical/eligibility decisions that define the sub-investigator role under ICH E6(R2) 1.56. See Clinical Research Coordinator (CRC).
- Not an instance
A monitor employed by the sponsor or a contract research organization (CRO) who visits the site to verify protocol adherence and data accuracy is not a sub-investigator -- a monitor is a sponsor-side oversight role (ICH E6(R2) 1.38) and is never listed on the site's own delegation log.
Editorial commentary
In US and ICH-harmonized clinical trial regulation, a sub-investigator is any individual member of the trial team at a site who is designated and supervised by the principal investigator (PI) to perform critical trial-related procedures and/or make important trial-related decisions — for example, associates, residents, or research fellows. The definition traces to ICH E6(R2) Good Clinical Practice, Section 1.56, and is the basis for how FDA regulations at 21 CFR Part 312 Subpart D treat delegated site-level trial conduct.
Where the role sits relative to the PI
The PI is the person who signs the FDA Form 1572 (Statement of Investigator) and personally assumes the regulatory obligations of 21 CFR 312.60 — conducting the study according to the protocol, protecting the rights and welfare of subjects, and controlling the investigational product. A sub-investigator does not sign the 1572 and does not independently assume those obligations; instead, 21 CFR 312.53(c) requires the PI’s Statement of Investigator to list the names of the sub-investigators who will be assisting in the conduct of the investigation. Because the PI’s signature covers the whole site team, the PI remains accountable for the sub-investigator’s delegated work, not just their own.
The delegation log defines the scope of the role
Naming someone as a sub-investigator on Form 1572 establishes who is on the team; it does not by itself specify what any individual sub-investigator is authorized to do. That specificity comes from the site’s Delegation of Authority (DoA) log, which ICH E6(R2) Section 4.1.5 requires the investigator to maintain as a list of appropriately qualified persons to whom significant trial-related duties have been delegated. A well-maintained DoA log typically records, per sub-investigator: the specific duties delegated (e.g., obtaining consent, conducting exams, assessing adverse events, making eligibility determinations), the effective date range of that delegation, and documentation that the person is qualified by training, experience, and (where applicable) licensure to perform those duties — consistent with the sponsor’s obligation under 21 CFR 312.53(a) to select only qualified investigators and sub-investigators.
What sub-investigators typically do, and what they don’t
Because ICH E6(R2) 1.56 limits the term to people performing critical trial-related procedures or important trial-related decisions, not every person working on a study qualifies as a sub-investigator. Administrative and data-management functions — scheduling visits, entering case report form data, managing regulatory binders — are typically performed by study coordinators or clinical research coordinators (CRCs), who are not sub-investigators unless separately delegated a qualifying clinical/decisional duty. Sponsor- or CRO-employed monitors who visit the site to check protocol adherence and source-data accuracy are likewise a distinct, sponsor-side role (ICH E6(R2) 1.38) and are never listed on a site’s own delegation log, since they are not part of the site team the PI supervises.
Why the distinction matters in practice
FDA and other regulatory inspectors reviewing a site’s conduct will cross-reference the delegation log against both Form 1572 and the source documentation for specific procedures — if a task is performed by someone whose delegation log entry doesn’t cover it (or who isn’t named on the 1572 at all), that is a common, citable GCP finding. Keeping the sub-investigator list on Form 1572, the scope of delegated duties on the DoA log, and actual site practice in alignment is a routine but essential part of investigator-site regulatory compliance, and typically falls to the PI and the site’s regulatory/study coordinator staff to maintain throughout the study, including whenever site staff turnover requires updating the delegation log or amending the 1572.
Related reading
See the CASRAI comparison of Co-Investigator vs. Sub-Investigator for how the sub-investigator role differs from a co-investigator (a role that, unlike sub-investigator, is not itself defined by ICH E6 or FDA regulation and varies by institution/grant convention).
Machine-readable encodings
Use in your systems
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