Direct comparison
Co-Investigator vs. Sub-Investigator
Co-Investigator is a general research role; Sub-Investigator is FDA/ICH-defined (21 CFR 312.53), named on Form 1572 and the Delegation of Authority Log.
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How do Co-Investigator, Sub-Investigator compare side by side?
The table below compares Co-Investigator, Sub-Investigator across 7 procurement-relevant dimensions, from formally defined by clinical-trial regulation? through qualification/training documentation required?.
Side-by-side comparison
| Dimension | Co-Investigator | Sub-Investigator |
|---|---|---|
| Formally defined by clinical-trial regulation? | No — general collaborative-research term, used across grants, publications, and multi-institutional studies | Yes — 21 CFR 312.3 defines the role within the "investigator" framework |
| Named on FDA Form 1572? | Only if also formally serving as a sub-investigator | Yes, listed by name (does not sign the form) |
| Requires a Delegation of Authority Log entry? | Only if delegated protocol-critical trial tasks | Yes — task-level entries with start/end dates, per ICH E6(R2) 4.1.5 |
| Governing framework | Institutional and funder practice; no single regulatory definition | 21 CFR 312.53 / 312.60; ICH E6(R2) Section 4.1.5 |
| Applies outside clinical trials? | Yes — grants, non-trial collaborations, publications | No — a clinical-trial-specific designation tied to IND-regulated investigations |
| Who retains ultimate accountability? | Depends on the funder/collaboration structure | The PI, per 21 CFR 312.60, regardless of delegated tasks |
| Qualification/training documentation required? | Varies by institution/funder | Yes — CV/training/licensure records expected in the Investigator Site File to support each delegated task |
Common questions
Common questions about Co-Investigator vs Sub-Investigator
Is every sub-investigator also a co-investigator?
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Informally, usually yes — most people functioning as sub-investigators are also described as co-investigators on the study team. But the reverse is not automatic: a co-investigator only becomes a sub-investigator once the PI formally delegates specific, protocol-critical trial duties to them, documented on the Delegation of Authority Log and, where applicable, listed on the FDA Form 1572.
Does a sub-investigator sign the FDA Form 1572?
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No. Only the Principal Investigator signs Form 1572. Sub-investigators are listed by name on the form but do not sign it themselves.
Who is accountable if a sub-investigator makes an error?
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The PI retains overall regulatory responsibility for the trial's conduct at that site under 21 CFR 312.60, even though a specific task was delegated to and performed by a sub-investigator. Delegation transfers performance, not the PI's accountability.
Does "Co-Investigator" mean the same thing on a grant as it does on a clinical trial?
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Not exactly — the underlying idea (a substantively contributing researcher who is not the lead PI) carries over, but a clinical trial adds a regulatory layer (FDA/ICH requirements) that a non-trial grant collaboration does not have.
