IQ OQ PQ: What Each Protocol Tests and How to Write Them

A new filling line goes in. Before it can run validated production batches, it has to pass three qualification stages. IQ, OQ, and PQ are not bureaucratic hurdles invented by regulatory bodies to create paperwork. Each one answers a specific question that the next stage cannot answer. If you skip one, the production output from that line is not validated. The regulatory consequence of running unvalidated production in a regulated environment is not an observation. It is a major finding.

The three stages are sequential for a reason. Installation qualification confirms the equipment is installed correctly. Operational qualification confirms it operates to spec. Process qualification confirms the process consistently produces acceptable product. Each one builds on the previous. You cannot demonstrate that a process consistently produces acceptable product on equipment that has not been confirmed to operate within specification.

What is IQ (Installation Qualification)?

IQ answers one question: was the equipment installed as specified? It does not test whether the equipment works. It tests whether the equipment was installed in accordance with the user requirements specification (URS), the vendor installation documentation, and the applicable site standards.

IQ checks five categories. Physical installation: is the equipment level within the vendor's specified tolerance? Is it anchored as required? Are the required clearances maintained for service access and ventilation? These are not administrative checks. A furnace installed out of level will produce non-uniform heat distribution. A compressor without specified service clearance cannot be maintained without moving the equipment.

Utilities: are the power supply, compressed air, cooling water, and any other utilities available at the equipment connection point at the specified conditions? Not the nominal site conditions. The actual measured conditions at the equipment. A specification of 6.5 bar compressed air requires a measured confirmation of 6.5 bar at the equipment inlet, not an assumption based on the header pressure.

Documentation package: are the P&IDs present and current? Are the calibration certificates for all instruments in the equipment present and covering the test period? Are the maintenance manuals, spare parts list, and software documentation included? An IQ without a complete documentation package is an incomplete IQ.

Instrument calibration status: every instrument on the equipment that will be used to measure a process parameter must be calibrated and within its calibration period before OQ begins. Calibration certificates must be included in the IQ report.

Software version: if the equipment runs on a control system, the software version is recorded and confirmed against the validated version specified in the URS or the vendor documentation.

IQ produces an installation qualification report. Every check is recorded as pass or fail, with any deviations documented and resolved before OQ begins. An IQ report with open deviations at the time OQ starts is not an acceptable IQ report.

What is OQ (Operational Qualification)?

OQ answers the next question: does the equipment operate within specified parameters? OQ does not use product. It is pure equipment verification. You are confirming that the equipment can achieve and maintain the process parameters it was specified to achieve, before you introduce any product into the equation.

The critical design principle for OQ is worst-case testing. OQ is not run at the nominal operating setpoint. It is run at the extremes of the specified operating range. If the process temperature range is 700 to 760 degrees C, OQ tests at 700 degrees C and at 760 degrees C, not at 730 degrees C. The logic is that if the equipment performs to spec at both extremes, it will perform to spec at every point within the range. Nominal setpoint testing tells you nothing about performance at the process limits.

OQ tests at least three categories. Process parameter control: at each extreme of the operating range, does the equipment achieve the setpoint and maintain it within the specified tolerance for the required duration? The acceptance criterion is a measurable pass/fail: temperature maintained within plus or minus 3 degrees C of setpoint for 60 minutes at both the low and high setpoints.

Alarm and interlock verification: every safety interlock must be tested by inducing the fault condition and confirming the interlock response. A high-temperature interlock is tested by raising the temperature above the trip setpoint and confirming the equipment responds as designed. These tests must be documented individually. "Interlocks tested and functional" is not a test record.

Equipment repeatability: the equipment is run through the same operating cycle multiple times to confirm that performance is consistent across cycles. A furnace that achieves setpoint on the first run but drifts on subsequent runs has a repeatability problem that OQ will catch before it manifests in production.

What is PQ (Process Qualification)?

PQ answers the final question: does the process consistently produce acceptable product? PQ uses real product, real operators, production-rate throughput, and production-grade input materials. Everything is real. The purpose is to demonstrate that under actual production conditions, the process delivers output that consistently meets specifications.

PQ requires multiple production runs. One run is not a demonstration of consistency. A single lot produced within specification could be the result of favorable random variation. Multiple lots produced within specification across different shifts, different operators, and different input material lots is a demonstration of process consistency.

The FDA process validation guidance states that the number of runs must be sufficient to demonstrate that the process will consistently produce product meeting predetermined specifications. In regulated environments, three production lots is the established minimum for most processes. Some processes require more, depending on the variability of the process and the criticality of the product. Three lots is the floor, not the ceiling.

PQ produces a process qualification report with statistical analysis. Process capability indices, specifically Cpk, are calculated to quantify the relationship between the process spread and the specification limits. A Cpk of 1.33 or higher is the standard expectation in regulated manufacturing. Confidence intervals on the key performance metrics are calculated to establish how reliable the Cpk estimate is across the three lots. Batch-to-batch variation is analyzed to confirm that the process is not drifting between lots.

The PQ report is the document that proves the line is ready for production. Without it, production output on that equipment is not validated, regardless of how well the equipment performed during OQ.

IQ OQ PQ: how they build on each other

Stage	What it proves	Required before starting	Failure consequence
IQ	Equipment installed correctly per spec	URS and vendor installation documentation	Reinstall or modify, repeat IQ
OQ	Equipment operates within spec across full range	IQ complete, all deviations closed	Root cause investigation, parameter changes, repeat OQ
PQ	Process consistently produces acceptable product	OQ complete, all deviations closed	Process development investigation, PQ repeated

The sequential dependency is strict. If the IQ reveals that the cooling water supply is 0.8 bar below specification, OQ cannot begin until the utility is corrected and the IQ check is re-performed with the correction documented. If the OQ reveals that temperature uniformity fails at the high end of the operating range, PQ cannot begin until the uniformity issue is resolved and OQ is repeated at the corrected conditions. A PQ performed on a process that has an open OQ deviation is a PQ conducted on a process that has not been confirmed to operate within specification.

What a good protocol looks like

Every IQ, OQ, and PQ protocol has the same structural requirements. The purpose statement defines exactly what the protocol is intended to prove. One to three sentences. "This IQ protocol confirms that filling line FL-004 was installed in accordance with user requirements specification URS-FL-004-001 and vendor installation documentation reference [vendor doc number]."

The scope section identifies the equipment by asset number, the process by name and area, and the facility by site designation. Any adjacent equipment or interfaces covered by the protocol must be named. Any equipment or interfaces explicitly excluded must also be named.

The responsibilities section assigns each role in the protocol execution to a specific job title. Who executes each test. Who witnesses the execution and countersigns the data. Who performs the independent review of the completed protocol. Who approves the final report. All four are different people in a well-controlled protocol.

The pre-execution checklist must be signed off before any testing begins. Every prerequisite from the previous stage must be confirmed. For OQ, the checklist confirms the IQ report is approved and all deviations are closed, all test instruments are calibrated and within their calibration period, and the test execution team has been trained on the protocol. Testing before the checklist is signed is a deviation from the protocol.

Test cases are the core of the protocol. Each test case covers one parameter or one function. The structure of each test case: test ID, objective, test method (step-by-step procedure for conducting the test), acceptance criterion (objective, measurable pass/fail statement), results table with fields for measured values and the instrument used, pass/fail field, and a deviation reference field for any out-of-specification result. The acceptance criterion must be written before testing begins. Writing the criterion after seeing the results is not a qualified test.

The deviation procedure defines two paths. Path one: the deviation is minor and testing can continue with the deviation documented. Path two: the deviation requires stopping the test, investigating, and obtaining approval before continuing. The protocol must define the boundary between these two paths before testing starts.

The summary and sign-off section records the overall pass/fail conclusion for the protocol, lists any open deviations and their resolution status, and carries the approval signatures with dates. A protocol that is signed off with open deviations is a protocol signed off prematurely.

Common protocol failures

Acceptance criteria written as "within spec" or "acceptable" with no objective measurement defined. Every acceptance criterion must be a measurable, specific pass/fail statement written before execution. "Within spec" is not a criterion. "Setpoint achieved within plus or minus 2 degrees C within 10 minutes, confirmed by three independent thermocouple readings" is a criterion.

OQ run at nominal setpoints only, not at worst-case conditions. The purpose of OQ is to confirm performance across the full operating range. Testing only at the center of the range tells you nothing about performance at the limits. This is the most common OQ protocol deficiency found in FDA inspections of medical device manufacturers.

PQ run with a single production lot. One lot demonstrates capability at one point in time. Three or more lots demonstrate consistency across time, operators, and input material variation. A single-lot PQ will be challenged in any serious regulatory inspection.

Calibration records not confirmed before protocol execution starts. The pre-execution checklist exists specifically to prevent this. A thermocouple that was calibrated 14 months ago against a 12-month calibration interval was out of calibration during OQ. The OQ data collected with that instrument cannot be verified as accurate. The OQ must be repeated.

For the documentation that surrounds the IQ/OQ/PQ process, including the SOPs that govern how the qualified process is operated after qualification is complete, see the guide on how to write a manufacturing SOP. The Aptibot documentation service writes IQ, OQ, and PQ protocols for regulated manufacturers, including the statistical analysis and reporting in the PQ qualification report. The ISO 13485:2016 standard and the FDA guidance together define the regulatory expectation for equipment qualification in medical device manufacturing. Both are worth reading in full if you are setting up a qualification program for the first time.