Final answer:
Autoclave tape is the only indicator mentioned that cannot be used to definitively verify sterility assurance of processed instruments because it does not indicate the length of exposure or the efficacy of sterilization.
Step-by-step explanation:
Sterility Assurance Indicators
All of the following indicators can be used to verify sterility assurance of processed instruments EXCEPT autoclave tape. Autoclave tape is a heat-sensitive material that changes color once a certain temperature is reached, indicating that a sterilization cycle has been run. However, it does not provide information on the length of exposure time or whether all microorganisms, such as spores, have been effectively killed. Hence, autoclave tape cannot definitively indicate that instruments have been sterilized successfully.
Other available indicators include biological spore tests and temperature-sensitive pellets within a Diack tube. These methods are much more reliable. Biological spore tests use resistant spores such as Geobacillus stearothermophilus and provide assurance by showing if the spores have been killed after the sterilization process. If the spores can still grow after the process, the items are not sterile. The Diack tube contains a pellet that melts at the specific temperature required for sterilization, which provides a visual cue that the required temperature was achieved.