DQ/IQ/OQ/PQ: Qualification that holds up in an audit

Qualification provides documented evidence that facilities, systems and equipment are fit for their intended use. The model is well established and described in EU GMP Annex 15. What decides the outcome, though, is not the model but the execution: what you test against, how deeply you test, and what happens to deviations.

The V model in four stages

• DQ (Design Qualification): the intended design meets the requirements set out in the URS. Verification happens on paper, before anything is purchased or built.
• IQ (Installation Qualification): delivered and installed as specified. Components, piping and instrumentation verified, calibrations recorded, materials and supplier documentation checked.
• OQ (Operational Qualification): function demonstrated across the entire intended operating range, including upper and lower limits. Only on that basis are SOPs and training finalised.
• PQ (Performance Qualification): performance is reproducible under real operating conditions, tested with production material or a qualified substitute. Where it can be justified, PQ is combined with OQ.

The chain of evidence decides

Each stage tests against the one before it, and everything ultimately tests against the URS. That chain is exactly what an auditor looks at: can every requirement be traced to the test that proves it, and on to the result that closes it? A traceability matrix is not a formality here, it is the tool that makes completeness demonstrable at all.

Test depth is a risk decision, not a matter of diligence.

Setting test depth on a risk basis

Annex 15 requires a risk-based approach and ICH Q9 supplies the method. Effort belongs where a failure reaches the product or the patient: critical process parameters, product contact surfaces, utilities and data paths. Standard components with no product contact do not need a test campaign of their own. Where the supplier has already tested robustly, for instance in FAT or SAT, those results can be leveraged under Annex 15 instead of repeated on site. What matters is that the rationale is documented, not that effort was saved.

Where qualification fails in practice

The patterns repeat: a URS that contains wishes rather than verifiable requirements. Test cases without acceptance criteria, where nobody can say when they have passed. Deviations that were recorded but neither assessed nor closed. And protocols written after execution. None of these is a technical problem, all four are questions of project leadership.

After qualification comes requalification

The qualified state is not a certificate, it is a condition that has to be maintained. Changes run through change control, periodic reviews check whether the assumptions still hold, and requalification follows risk rather than the calendar. A facility that is qualified but not monitored in live operations is exposed at the next audit.