How to Validate an Autoclave: Performance Qualification (PQ)

An autoclave undergoes qualification testing in order to validate and verify that it’s performing consistently and properly. In previous posts, we outlined the first two qualification tests known as Installation Qualification (IQ) and Operation Qualification (OQ). In this post we will review Performance Qualification (PQ) as a final critical step in validating your autoclave.

What is Performance Qualification (PQ)?

PQ demonstrates that the autoclave not only runs the required cycles, but provides the required result: sterility. The PQ process involves testing the loads that must be successfully sterilized in the autoclave. The prerequisites for PQ are successful IQ and OQ.

Performance Qualification (PQ) – A process which obtains and documents evidence that the autoclave, as installed and operated in accordance with operational procedures, consistently performs in accordance with predetermined criteria and thereby meets its specification. [ISO TS 11139:2006, definition 2.30]

Sample Test Protocol

PQ is comprised of at least three repeated tests for each defined load. The critical aspect of the tests is to validate sterility in each of the loads. Each load type will have its own challenges so it’s important that each is specified with information such as: number and type of objects being sterilized, sterile barrier material used, and in certain cases, orientation of the objects being sterilized in the autoclave.

Here is a sample PQ test protocol:

1. Objective

The Objective is to prove sterilization of the specified load. The sterility assurance level may derive from a standard, from a client SOP or specification, or from a manufacturer’s specification. Specific citations to any of these should be made in this section.

2. Procedure or Setup

The Procedure or Setup explains how to setup and execute the test. The following specifications should be noted here:

• The type of cycle (dynamic air removal, gravity, liquid, air-overpressure during cooling, air overpressure support, water cascade, etc.) including all critical parameters
• Any equipment needed for the test
• The number and location of each item in the load
• If a mixed load is to be run, the number of each item and the items’ locations should be specified.
• Locations of the indicators and datalogger probes – these should be placed in “worst-case” locations in the load to provide assurance that the entire load is sterilized
• Sterile barrier materials or vessel covers (like aluminum foil for flasks), as well as their application to the items closed by them
• A step-by-step listing of how to carry out the test

3. Acceptance Criteria

The Acceptance Criteria section lists the required result or range of results. Examples of acceptance criteria for Performance Qualification involve sterility and temperature. For example, if the “acceptable criteria” for the temperature range within the chamber during sterilization is -0/+3°C relative to the actual set point, then the chamber temperature at all measured points must be within that range for a successful outcome to be recorded.

Another example of a critical “Acceptance Criteria” is sterility, which is proven through the use of biological indicators (BIs). The obvious result is that there should be no surviving spores on the BI. If there are survivors, an examination of the BIs should be undertaken to ensure that the resistance (i.e. D-value) of the BIs is not greater than those of the BIs used in the original cycle development.

4. Result Record

The Result Record is where all of the test data is recorded. At least three iterations are typically run for process tests. Any failure to comply with the acceptance criteria makes an “iteration” a failed test. The required number of iterations must be run successively with successful outcomes for the test to be considered a pass. The record must include:

• Sterilizer cycle tape or electronic record
• Biological (and chemical, if used) indicator results
• Datalogger results and their compliance with the Acceptance Criteria
• Analysis of the datalogger (thermocouple) records for accumulated lethality (Fo) and compliance with allowable load temperature ranges in the exposure phase

5. Verification

After the testing is done, the results are typically reviewed for compliance with the acceptance criteria. The review is finalized in this section with signatures from the person who ran the test and, preferably, with countersignature of a second person or manager.

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Sterility Testing & Record Keeping

Sterilization cycles are to be run sequentially and the load setup should follow the Procedure or Setup section of the test. Indicators and data logger probes are to be placed as specified. Sterile barrier or closure materials are to be applied as specified. If sample loads are to be reused, they should be allowed to cool to a specified temperature (optimally room temperature) between cycles to provide a real-world thermal load for the sterilizer and a real-world exposure for the indicators.

In all tests, record keeping is essential to the integrity of the test. Records may include cycle tape printout from the sterilizer, data logger data files, photos, sketched diagrams, etc. These must be attached or provided with the report, with each identified by the section of the PQ protocol to which it applies. Any electronic data records should be provided in a non-volatile form with the final report, i.e., as a CDROM or DVDROM, or via cloud storage.

A more extensive list of the required records is listed here:

• A catalog of who carried out the testing, the verification of results, and approvals with initials and signatures.
• A listing of reference or other test equipment, manufacturer, model, serial number, and calibration due date, if applicable.
• A listing of biological indicators and chemical indicators (if used), including manufacturer, model number, lot number, D-value, and nominal population.
  • If inoculum is used, a recovery study shall be done to ascertain the actual recoverable population of the indicators; also, a growth promotion study shall be done to ensure that the item upon which the inoculum is deposited does not have a negative effect on outgrowth of the indicator organism
• A calibration record for test equipment (e.g. thermocouples) if done at the work-site, both before and after a series of tests and/or after the entire test protocol is performed.

A well-executed PQ will enable you to demonstrate and document that the autoclave can execute the desired processes and provide the sterility assurance level that is required for your application. PQ is generally the final step in qualification. This testing creates an unassailable baseline level of proof of the autoclave’s ability to do the specified job, and is the basis for requalification at periodic intervals.

If you have additional validation questions or any questions related to autoclaves in general, please contact us for more information.

(Co-written by Jonathan A. Wilder, Ph.D., Stericert div. of H & W Technology)