PQ is the process of obtaining and documenting evidence that the sterilizer will consistently produce reproducible results when operated in accordance with the pre-defined acceptance criteria within the process specification.

The extent of the PQ required will depend on the type of sterilizer and the nature of the load.

ISO 17665:2024 - 9.4 

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 Users should adopt the following procedure for every sterilizer:

• Establish a list of potential product families and their relationship to the validation loads qualified during validation.
• Establish a list of the different loading conditions to be processed in the sterilizer. Each production load should correspond to one of the listed loading conditions.
• Determine whether each loading condition presents a greater or lesser challenge to the process than the small and full loads used in the thermometric tests carried out during validation.
• Where the loading condition is a lesser challenge than the validation loads, the results of the validation tests may be used as PQ data.
• Where the loading condition is a greater challenge than the validation loads, PQ tests should be carried out.

Where PQ tests have not been undertaken and no PQ report will be created, the AE(D) or your sterilization SME should satisfy themself that the range of installation, operational and periodic tests undertaken is representative of the range of loads and product families processed by that particular sterilizer. This should be documented.  

The user should decide which loading conditions require PQ tests for all sterilizers following advice from the AE(D) or your sterilization SME.

In cases of doubt, advice should be sought from the AE(D).

PQ tests should be performed as part of the initial validation procedure, as part of any repeat validation procedure, and whenever the user judges that a new loading condition calls for a new PQ test.

Where a new load is not covered by an existing PQ report, full PQ tests should be conducted.

When designing a new loading condition, it is important that the correct packaging is specified with the load. The packaging specification should not then be altered without repeating the PQ procedure unless the loading condition with new packaging can be demonstrated to be covered by an existing PQ report.

Position of PQ sensors

Temperature sensors should be suitable for the application and conform to the requirements of the relevant standard, EN 60751 or EN 60584.

Temperature sensors should be placed in the following positions:

• one on/in each of three items that are slowest to attain the sterilization temperature;
• one on/in each of three items that are fastest to attain the sterilization temperature;
• if the load consists of fewer than six items, one on/in each item;
• if the load includes lumen devices, temperature sensors should be placed to monitor the environment within the lumen rather than the device’s surface, at the most challenging position within the device. In cases where temperature cannot be used to determine the presence of residual air (for example a narrow lumen or metal device in which the residual air rapidly attains steam temperature), alternative sensor technology should be used. Examples include chemical and biological indicators.

The fastest and slowest items should have been identified as part of the design of the loading condition.

Sensors should be in good thermal contact with the fluid or device they are monitoring and be placed in contact with the part of the item that is slowest to heat up.

Thermometric test for PQ

Method

Place a sensor in the reference measurement point – the point where the cycle control temperature sensor is located.

Record the loading condition and the positions of the sensors and probes in sufficient detail for the test to be replicated. Digital photography provides a useful record.

Connect a pressure recorder or pressure-recording instrument to the chamber.

Select the operating cycle that will be used for the production load.

Start the cycle.

Result

The test should be considered satisfactory if the following requirements are met:

• throughout the holding time, the temperature measured at the reference measurement point of the sterilizer chamber, any temperature measured within the test pack, load and chamber, and the saturated steam temperature calculated from the measured chamber pressure should:
• the holding time, as determined from the measured temperatures, is not less than that specified for the required sterilization temperature;
• the requirements of the automatic control test;
• be within the sterilization temperature band;
• not differ from one another by more than 2ºC;
• the indicated and recorded temperatures from the chamber and load items are within 2ºC of the temperature measured at the reference measurement point;
• the indicated and recorded chamber pressures are within 0.05 bar of the measured pressure;
• at the end of the cycle:
• the temperature sensors have remained in position.

If the test is satisfactory, it should be performed twice more to check for reproducibility and establish permitted tolerances. If the sterilizer fails to meet the requirements of the test it is possible that the sterilizer is not capable of processing the load. Advice should be sought from the AE(D).

Microbiological test for PQ

This test is designed to be used in exceptional circumstances as an additional PQ test for steam sterilizers. The microbiological test should ideally follow a satisfactory thermometric test, using the identical loading condition and operating cycle. There may be situations where thermometric tests are not possible, for example with narrow-lumened instruments, where it is not physically possible to place a thermocouple or temperature sensor into the lumen without altering the nature of the load. 

Result

The test should be considered satisfactory if the following requirements are met:

• during the whole of the cycle the values of the cycle variables as shown on the batch processing record (BPR) are within the permitted tolerances established during the thermometric PQ test;
• the requirements for microbiological tests are met.

Return to Schedule of Tests