False negative interpretation of biologic indicators or the importance of using two biologic indicator test strips.

The use of at least two biologic indicators to monitor a sterilization process greatly enhances failure detection. A retrospective study of a sterilization monitoring service's database revealed that 48.7% of tests using two test strips were single-strip positive. This indicates that there is a nonuniformity in the sterilization conditions within the sterilizer chamber and that there is a need for at least two test strips to detect this nonuniformity.