Phase 1
Initial Assessment and Lab Investigation
1Identify and document the anomalous result
Result documented immediately upon identification, with the investigation record opened before any further sample handling or retesting occurs.
21 CFR 211.192
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2Secure samples and preserve original data
Retained samples secured and all original raw data, instrument printouts, and bench records preserved before proceeding, protecting the investigation's evidentiary basis.
21 CFR 211.194
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3Conduct the Phase I laboratory investigation
Analyst technique, equipment function, reagent and media quality, calculation accuracy, and method suitability reviewed for a plausible laboratory explanation.
FDA OOS Guidance 2006
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Is a documented, objective, assignable laboratory cause identified?
YES → Invalidate, retest if justified
NO → Proceed to Phase II
Phase 2
Manufacturing and Process Investigation
4Expand investigation into manufacturing records
Batch record, equipment logs, environmental monitoring data, and process parameters from the affected batch reviewed for any contributing factor.
FDA OOS Guidance 2006
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5Review personnel, materials, and environment
Personnel involved, raw material lots used, and environmental conditions during the affected process step reviewed for any plausible source of the finding.
21 CFR 211.192
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6Interview involved personnel
Personnel directly involved in the affected process step interviewed to capture contemporaneous observations not necessarily reflected in written records.
FDA OOS Guidance 2006
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7Evaluate related batches for potential impact
Other batches manufactured with the same materials, equipment, or process conditions evaluated to determine whether the finding has implications beyond the single batch.
21 CFR 211.192
Phase 3
Root Cause and Impact Assessment
8Apply a structured root cause methodology
Formal tools such as the 5 Whys or a fishbone diagram applied systematically rather than relying on an unstructured narrative conclusion.
ICH Q10
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9Determine the most probable root cause
Root cause determined and supported by objective evidence gathered during the investigation, rather than the most convenient or least disruptive explanation.
FDA OOS Guidance 2006
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10Assess batch disposition and broader impact
Disposition decision made for the affected batch and any related batches, with the conclusion and supporting rationale fully documented for quality unit review.
21 CFR 211.192
Phase 4
CAPA and Closure
11Develop and implement CAPA
Corrective actions address the immediate cause; preventive actions address the systemic factors that allowed the cause to occur, both tracked to implementation.
ICH Q10 Section 3.2.2
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12QA review and final closure
Quality unit reviews the complete investigation record, confirms the conclusion is adequately supported, and formally closes the investigation.
21 CFR 211.22
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13Verify CAPA effectiveness and update trends
CAPA effectiveness verified through follow-up monitoring, with the investigation and its outcome added to the relevant trend dataset for ongoing review.
ICH Q10
Investigation Outcome Requirements
Invalidation Requires Objective Evidence
A result may only be invalidated with documented, objective evidence of an assignable laboratory error, not on the basis that the result seems inconsistent with expectation alone.
FDA OOS Guidance 2006
Retesting Requires Justification
Any retesting performed must be scientifically justified and pre-defined in procedure, not conducted simply until a passing result is obtained.
FDA OOS Guidance 2006
Inconclusive Findings Are Handled Conservatively
Where no root cause can be established, the original result stands and the batch disposition decision reflects that unresolved uncertainty.
21 CFR 211.192
Root Cause Methodology Tools
5 Whys
Repeated questioning that moves past the immediate symptom to a deeper systemic cause, useful for straightforward, single-path investigations.
Fishbone (Ishikawa) Diagram
Structured visual tool organizing potential causes into categories such as people, method, machine, material, and environment.
Fault Tree Analysis
Top-down logical diagram tracing how combinations of contributing factors could lead to the observed failure, useful for complex, multi-factor events.
Timeline Reconstruction
Chronological reconstruction of events surrounding the affected batch or sample, useful for identifying a specific point where a deviation from procedure occurred.
Comparative Analysis
Comparison against similar batches or samples that did not exhibit the finding, helping isolate the specific variable that differed.
Documentation Requirements
Contemporaneous record-keeping
Investigation findings documented as they are gathered, not reconstructed from memory after the investigation has largely concluded.
Objective evidence for every conclusion
Each conclusion in the investigation record supported by specific, referenced evidence rather than unsupported assertion.
Complete chronology
Investigation record includes a clear timeline from initial identification of the anomalous result through final closure.
Cross-functional sign-off
Investigation reviewed and approved by all relevant functions, including quality, before final closure and disposition.