Investigations are a top FDA finding

In FY2025, inadequate investigations under 21 CFR 211.192 were the second most-cited drug observation, with 164 citations, behind quality unit procedures under § 211.22(d) with 243 (GMP Insiders). In 2025 warning letters, § 211.192 drew 22 citations (Pharmaceutical Online), with the authors calling for investigations “supported by a robust root-cause analysis that drives effective corrective and preventive actions.”

What the regulations require

RequirementSource
”Any deviation from the written procedures shall be recorded and justified.”21 CFR 211.100(b)
The quality unit reviews production records to assure “that no errors have occurred” or, if they have, “that they have been fully investigated.”21 CFR 211.22(a)
Unexplained discrepancies and batch failures must be investigated “whether or not the batch has already been distributed,” extended to other batches and products that may be associated, with a written record of conclusions and follow-up21 CFR 211.192
Investigation effort “should be commensurate with the level of risk”; use “A structured approach” to determine root causeICH Q10

Out-of-specification results: the two phases

FDA’s OOS guidance (revised May 2022) sets two phases (FDA):

  1. Phase I (laboratory). “an initial assessment of the accuracy of the laboratory’s data.” Results “should not be attributed to analytical error without completing an investigation.”
  2. Phase II (full-scale). When no lab error is confirmed, “a full-scale OOS investigation using a predefined procedure should be conducted” to “identify the root cause,” extended “to other batches or products that may have been associated with the specific failure.”

The “human error” trap

FDA keeps rejecting unsupported human error conclusions. A 2025 warning letter faulted a firm for not showing “how you determined human error was the sole reason for the failed tests” (FDA Warning Letter). Industry experts agree: “human error is always a symptom — a starting point — for an investigation and is never the answer or cause” (Pharmaceutical Online). ECA puts it simply: human error “rarely is it the actual root cause” (ECA).

Deviation investigation checklist

Immediate response (day 0–1)

  • Deviation recorded with what, where, when and who discovered it
  • Affected materials, batches and equipment identified and quarantined as needed
  • Initial risk classification (critical, major, minor) with rationale

Investigation

  • Investigation team includes process, quality and, where relevant, lab experts
  • Timeline of events reconstructed from batch records, logs and audit trails
  • Structured root cause method used and documented (for example event and causal factor charting, fault tree or 5 Whys with evidence)
  • Each candidate cause confirmed or ruled out with data
  • If human error is involved, contributing factors examined: procedure clarity, training, workload, equipment design
  • Scope extended to other batches, products and sites that may be affected

Impact and disposition

  • Product quality impact assessed against specifications and stability
  • Regulatory impact assessed (filing commitments, field alert reporting)
  • Batch disposition decided by the quality unit with documented justification

CAPA and closure

  • Corrective and preventive actions address the confirmed root cause
  • Effectiveness criteria defined before closure
  • Investigation closed within the SOP timeline, or extension justified
  • Trend data updated for recurring deviations

Deviation investigation report template

SectionContents
1. SummaryDeviation number, product, batch, date, classification
2. DescriptionFactual account of what happened vs what should have happened
3. Immediate actionsContainment and quarantine
4. InvestigationMethod, data reviewed, timeline, causes considered
5. Root causeConfirmed cause with supporting evidence
6. ScopeOther batches, products, sites assessed and results
7. Impact assessmentProduct quality, patient safety, regulatory
8. CAPAActions, owners, dates, effectiveness criteria
9. Conclusion and dispositionQuality unit decision and sign-off

Review investigations at scale

Recurring 211.192 findings often come from investigations that look complete but do not prove their conclusions. AI document assessment can review closed deviation reports and your investigation SOP against 211.192, the OOS guidance and ICH Q10, flag unsupported “human error” conclusions or missing scope checks, and cite the passage behind every finding.

Run a sample regulatory document assessment on a set of closed deviations. AskDona shows the evidence; your QA team decides.

FAQ

What does 21 CFR 211.192 require? Investigation of unexplained discrepancies and failures, whether or not the batch has been distributed, extended to related batches, with written conclusions and follow-up (eCFR).

What are the phases of an OOS investigation? Phase I assesses laboratory data accuracy; Phase II is a full-scale investigation to identify the root cause (FDA).

Is human error an acceptable root cause? Only with evidence, and usually as a symptom of deeper causes. FDA has rejected unsupported human error conclusions in warning letters.

How deep should an investigation go? ICH Q10 says effort should be “commensurate with the level of risk” (ICH Q10).

References

All pages opened and checked by October 9, 2026.

SourceTypeDateUsed for
eCFR: 21 CFR Part 211Regulation textCurrent§§ 211.22, 211.100
eCFR: 21 CFR 211.192Regulation textCurrentInvestigation requirements
FDA/ICH: Q10Regulator guidanceApr 2009Risk-based investigation
FDA: OOS guidance Rev. 1Regulator guidanceMay 2022Phase I and II
GMP Insiders: FY2025 observationsIndustry analysisJan 5, 2026211.192 citations
Pharmaceutical Online: 2025 warning lettersExpert columnDec 15, 2025Warning letter data
FDA Warning Letter 320-25-88 (ProPublica copy)RegulatorJul 2, 2025Human error criticism
Pharmaceutical Online: Beyond human errorIndustry roundtableNov 16, 2020Root cause methods
ECA: Rethinking deviation managementIndustry associationc. 2025Human error