IQ, OQ, PQ Explained: Validating Systems for GxP
IQ, OQ and PQ are the three qualification stages that show a system or piece of equipment is installed correctly, works as intended, and performs in real use. They appear in equipment qualification and in computer system validation, and inspectors expect the evidence to be structured, documented and traceable to requirements. This guide explains what each stage proves, how they differ, and where they fit.
The three stages
- 1
IQ, Installation Qualification
Documented evidence that the system or equipment is installed correctly and matches the specification: the right version, configuration, connections, utilities and environment. IQ answers, is it installed the way it should be?
- 2
OQ, Operational Qualification
Documented evidence that the system operates as intended across its intended range: functions work, limits and alarms behave, security and access controls do what they should. OQ answers, does it work the way it should?
- 3
PQ, Performance Qualification
Documented evidence that the system performs consistently in its real operating environment, with real processes, data and users, over time. PQ answers, does it perform in actual use?
How they differ
| Stage | Question | Typical evidence |
|---|---|---|
| IQ | Is it installed correctly? | Build and version records, configuration, connectivity, environment checks. |
| OQ | Does it operate as intended? | Function tests across the range, limit and alarm tests, access-control tests. |
| PQ | Does it perform in real use? | Runs with real processes and data, performance over time, user workflows. |
Where IQ OQ PQ fit in validation
In computer system validation, IQ, OQ and PQ sit inside a validated lifecycle that starts from requirements and risk. Requirements are defined, risks assessed, and each qualification test traces back to a requirement, so an inspector can follow the thread from a requirement to the evidence that it was met. The point is not the paperwork for its own sake; it is a defensible chain of evidence that the system does what the regulated process needs.
Frequently asked questions
IQ is Installation Qualification, OQ is Operational Qualification, and PQ is Performance Qualification. Together they provide documented evidence that a system or piece of equipment is installed correctly, operates as intended, and performs consistently in real use.