Direct comparison
PI vs. Sub-Investigator: Roles Compared
PI signs FDA Form 1572 and holds non-delegable accountability (21 CFR 312.60); Sub-I performs delegated tasks per the Delegation of Authority Log.
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How do Principal Investigator, Sub-Investigator compare side by side?
The table below compares Principal Investigator, Sub-Investigator across 7 procurement-relevant dimensions, from signs fda form 1572? through governing citations.
Side-by-side comparison
| Dimension | Principal Investigator | Sub-Investigator |
|---|---|---|
| Signs FDA Form 1572? | Yes — the PI is the signatory of record for the site (21 CFR 312.53(c)) | No — listed by name on the 1572 but does not sign it |
| Ultimate regulatory accountability to FDA/sponsor | Yes, non-delegable, under 21 CFR 312.60, regardless of what is delegated | No — accountable to the PI for delegated tasks, not to FDA/sponsor for overall site conduct |
| Where scope of work is documented | Protocol, 1572, and overall investigator agreement | Delegation of Authority (DoA) Log, per ICH E6(R2) 4.1.5, task by task |
| Can independently perform protocol-critical procedures? | Yes, inherently | Yes, if delegated and documented — can include complex clinical judgment tasks |
| Requires their own 1572? | Always, for each site they serve as PI | Only if they themselves become PI of record for a study — not triggered by task complexity alone |
| Supervises whom | The full site investigator team, including all Sub-Investigators | Works under the PI's supervision; may in turn oversee other delegated staff for specific tasks |
| Governing citations | 21 CFR 312.53, 312.60; ICH E6(R2) Section 4 | ICH E6(R2) Section 1.56 (definition), 4.1.5 (delegation); named per 21 CFR 312.53(c) |
Common questions
Common questions about Principal Investigator vs Sub-Investigator
Can a Sub-Investigator sign informed consent forms?
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Only if that specific task is delegated to them and documented on the DoA Log, and permitted under applicable institutional/IRB procedures — the 1572 alone does not authorize it.
Does adding a Sub-Investigator require notifying FDA?
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It requires updating the DoA Log and investigator site file, and typically notifying the sponsor and IRB, but not a new or amended 1572, since Sub-Investigators are not 1572 signatories.
Is Co-Investigator the same as Sub-Investigator?
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No. Co-Investigator is a general academic/grants term with no clinical-trial-specific regulatory definition; Sub-Investigator is the FDA/ICH-defined trial role. See the separate Co-Investigator vs. Sub-Investigator comparison.
Who is accountable if a Sub-Investigator's delegated task goes wrong?
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The PI retains site-level regulatory accountability under 21 CFR 312.60 even for properly delegated tasks; this doesn't erase the Sub-Investigator's own professional responsibility for their own performance.
