Radiation Dose Audit Failures: Truth and Consequences

The validation of a radiation sterilization dose involves an initial sterilization dose determination as well as maintenance of that sterilization dose. The procedures for maintenance of the sterilization dose typically include the periodic use of two types of tests: bioburden and dose audits. The details for the procedures are outlined in the ISO radiation sterilization standards. These documents also provide guidelines for recommended actions in response to the results of the two tests. The results for the dose audit are based on the number of positive tests of sterility (TOS) for products that have been irradiated at a verification or experimental dose. When the dose audit yields TOS positives, it is often thought that they indicate a sterilization failure and nonsterile product. The belief that any TOS positive is a failure is an incorrect assumption because of the statistical basis used for the determination of the sterilization dose. This article will outline the truth of what dose audit TOS positives mean in terms of the sterility assurance of product, as well as the consequences of TOS positives.