False positive results of Bowie and Dick type test used for hospital steam sterilizer with slower come-up ramps: A case study

Objective
To determine if the standardized B&D type test for hospital steam sterilizer is correctly indicating cycle failures in slower come-up ramps cycles.
Methods
Two commercially available B&D type test were challenged in a quality control sterilizer. A common failure was simulated in triplicate cycles, using a standardized cycle configuration, and then compared to triplicate cycles of a common cycle configuration. Tests procedures were conducted according to B&D manufacturer test standard and results were compared to standardized endpoint specifications.
Results
We found that B&D type tests are only capable of detecting the presence of non-condensable gases if the sterilization equipment is adjusted to meet all the cycle requirements of the test. False positive results were obtained with come-up ramp time of 3 min. Correct results were only obtained with come-up ramp of 1.7–1.9 min.
Conclusions
Until the ISO 17665 and AAMI ST-79 standards are revised, equipment qualification experts should observe come-up time duration criterion for B&D type test cycles according to ISO 11140–4. Sterile Processing Department professionals must add the come-up ramp criterion to cycle evaluation before clearing the equipment for routine use. This will allow B&D correct performance, reducing the infection risk from unsterilized medical device.