Opinion: Validation is key to compliant sterilisation processes

Autoclave calibration and validation are vital to many activities and Paul Birchmore, Sales & Marketing Director, Astell Scientific explains the difference between them

Sterilisation is critical to many of the activities that are carried out in cleanrooms, from life science research to contact lens manufacturing, and steam sterilisation using an autoclave is the preferred technique.

A failure of product sterilisation has far-reaching consequences, but a failure of a laboratory steriliser can produce spurious results causing unnecessary product wastage or loss of research data. How can you be certain that your autoclave is working properly?

When using steam for sterilisation, it is critical to know that the correct pressure and temperature have been reached and that both parameters have been held for long enough to ensure the total destruction of any microorganisms, bacteria and spores. This means that the instrumentation (temperature and pressure sensors and timers) that controls your autoclave must be functioning correctly and producing accurate readings. In other words, they must be properly calibrated.

Understanding calibration

Calibration is about checking that the autoclave instruments read accurately by comparison against a known standard and that the chamber reaches the required temperature for the required time. This testing methodology should be carried out using the protocols that are set out in the international standard ISO/IEC 17025:2017.

The test can be carried out at a number of different sterilisation temperatures, depending on the customer's requirements, and confirms that the machine has been calibrated in accordance with UKAS standards by an accredited calibration laboratory such as Astell Scientific. Upon successful completion, the laboratory issues a certificate of calibration. However, a successful calibration only confirms that the instruments and controls are operating correctly.

Validation

Multipoint validation is a more detailed test. It records temperature readings at 12 points within a specific customer load in the autoclave chamber over a specified time, and it may be repeated for different loads.

Steam penetration and air removal are of key importance, so tests are, as far as possible, carried out under worst-case conditions. Typically, it would be an example of the largest load the customer is likely to run.

Multipoint testing enables dedicated sterilisation programmes for "difficult" loads with complex shapes or varying heat capacity

Analysing the results from multipoint testing enables the validation engineer to set up dedicated sterilisation programmes for those loads, which is particularly advantageous when "difficult" items, such as those of complex shapes or varying heat capacity, are to be sterilised.

Once testing is complete and the cycles have been set up, the validation engineer will issue a certified test report detailing the results from testing. These will include details of cycle times and temperatures, along with photographs of the way in which the contents have been loaded into the chamber to ensure that the operators load the machine in the same way each time.

Such validation reports are valuable in providing continuity, particularly when an autoclave has several different users, and assist in ensuring repeatability and correct use of a machine.

Paul Birchmore,
Astell Scientific Sales & Marketing DIrector

Multipoint validation tests should be completed at regular intervals using a UKAS accredited testing laboratory. Once again, the protocols set out in ISO/IEC 17025:2017 should be adhered to.

Failure to meet sterility requirements can have serious repercussions. Regular calibration is a clear routine necessity, but validation ensures compliance.

The validation process may sound complicated, but it pays dividends. It establishes documented evidence that shows a high degree of confidence that the sterilisation process will be performed consistently. Astell Scientific has the experience and knowledge to assist customers in specifying the equipment you need. Even if the autoclave is brand new and has been functionally tested and calibrated at the manufacturer's works prior to dispatch, it is the user's responsibility to ensure that it is operated onsite as intended.

Validation is the key to meeting this responsibility and, to this end, regular testing of an autoclave's performance by an accredited company is recommended as good practice.