Recently we wrote about common radiation validation approaches and the advantages to medical device manufacturers of understanding those approaches. (See, Turn On the kGys to Sterilize those Devices)Advantages of a good understanding included: a better ability to make product development decisions and decisions on proper radiation doses, and a greater ability to plan for samples and sterilization costs.
But, what happens if you get a failure either during the validation process or during a routine dose audit?
Failures can and do arise. The first thing to remember is all failures are different. There is no benefit in jumping to conclusions or making assumptions and guesses.
Many failures can be identified and corrected when approached properly. You can always consult with us at Nelson Laboratories if you have any questions. Below is a list of the most common causes of failures and a brief description of what to do.
- Increased bioburden count. This occurs when for whatever reason the bioburden count is higher now than it was during the initial validation. In this case you can investigate and fix the bioburden problem or re-establish a higher sterilization dose of radiation.
- Increased bioburden resistance. This occurs when the bioburden count remains the same, but more radiation-resistant microorganisms are now present. Here you can also find and fix the problem or increase the radiation dosage.
- Underestimation of bioburden. If the bioburden count is underestimated there are actually more microorganisms on the product than the results indicate. This can be fixed by performing a more extensive recovery efficiency test to determine the proper bioburden and radiation dosage or may include using a different bioburden test method to increase the test sensitivity.
- Contamination during testing. Some devices need a lot of manipulation during the test of sterility. The most common manipulations are disassembly and cutting to fully expose all critical surfaces to the test medium. If this is done after delivery of the verification dose and during the test of sterility the manipulation can introduce microorganisms. The best approach here is to prepare samples (i.e. perform the necessary manipulations) prior to delivery of the verification dose.
- Shipping etiquette. Once samples are irradiated the outside of the packaging can become contaminated during shipping, which can introduce microorganisms into the sterility test environment. To prevent this, provide multiple barriers in dosing and shipping by lining the shipper box with two plastic bags before placing the samples into the box.
These are some of the most common causes of failures. A couple of lesser common ones include failed packaging or incorrect dosing. These causes, along with numbers four and five above, are not true failures (meaning that the sterility growth is not due to microorganisms surviving the radiation dose). If you investigate and implement corrective action you can repeat the test and use the repeat results as the dose audit.