What is root cause analysis in GMP?

Short answer

Root cause analysis in GMP is an evidence-based investigation used to understand the underlying and contributing factors that allowed a deviation, defect, failure or recurring problem to occur. The conclusion should follow from the evidence, and any resulting actions should address the identified cause rather than only correcting the immediate symptom.

What this means in practice

A useful investigation separates the event itself, its direct cause, contributing factors and wider system weaknesses. It should test reasonable hypotheses, consider related events and trends, and explain how the available evidence supports the final conclusion.

If a definitive root cause cannot be established, the record should be transparent about that uncertainty. The most likely cause or causes may still be identified and addressed, provided the rationale and limitations are documented.

Regulatory guidance and investigation tools

EU GMP Chapter 1 is regulatory guidance. It expects an appropriate level of root cause analysis during investigations of deviations, suspected product defects and other problems. Where human error is suspected, the conclusion should be justified and process, procedural or system failures should not be overlooked.

EU GMP does not mandate one universal investigation method. Techniques such as a structured timeline, the 5 Whys or an Ishikawa diagram can help organise thinking, but completing a tool does not by itself demonstrate that the correct cause has been found.

A defensible root cause analysis normally includes

A precise, factual problem statement.

Preservation and review of relevant records, data, interviews and physical evidence.

A timeline showing what happened before, during and after the event.

Assessment of equipment, materials, methods, environment, people, procedures and management systems as relevant.

Testing of plausible causes against the evidence.

Review of similar events, adverse trends and previous CAPA.

A documented conclusion, including uncertainty and limitations.

Actions linked directly to the identified or most likely causes.

Common weaknesses

Naming human error without examining why the error was possible.

Selecting a preferred cause before the evidence has been gathered.

Stopping at the first plausible explanation.

Using a diagram as evidence instead of supporting the conclusion with records and facts.

Raising generic retraining actions that do not address the underlying system.

Closing the investigation while repeat events or contradictory evidence remain unexplained.

Questions to ask internally

Does the problem statement describe the actual event without assumption?

What evidence supports and contradicts each hypothesis?

Have related processes, batches, systems and sites been considered where relevant?

Would removing the proposed cause reasonably prevent recurrence?

Are the resulting actions proportionate, owned and capable of effectiveness verification?

How W2 can help

W2 Cleanroom Consulting can independently review investigation logic, challenge unsupported human-error conclusions, examine links to cleanroom control and validated state, and assess whether proposed CAPA addresses the evidence. The client remains responsible for Quality decisions, investigation approval, licence obligations and regulatory correspondence.

Need an independent review of a difficult investigation?

Contact W2 Cleanroom Consulting at info@w2cleanrooms.com to discuss root cause review, recurring deviations, inspection response or remediation support.

Prepared and reviewed by: W2 Cleanroom Consulting GMP team. Last reviewed: 24 July 2026.