During the final rapid method session at this year's PDA Annual meeting, I provided an overview of the compendial, regulatory and technical reasons why interference testing, including false positive and false negative assessments, should be conducted during the validation of RMMs. False positives occur when a positive detection signal and/or apparent microbial count is obtained when viable microorganisms are not actually present. This can occur for different types of rapid methods but can be more apparent when using a technology that does not rely on microbial growth. This may result in an overestimated of viable counts. Alternatively, a false negative occurs when no detection signal and/or microbial count is observed when viable microorganisms are actually present. This may occur, for example, when test sample components interfere with the detection and/or counting or microorganisms. In this case, an underestimation of viable counts can occur.
I finished my presentation with an overview of a case study on false positive testing using BioVigilant's IMD-A, a real-time environmental monitoring technology that simultaneously detects, sizes and enumerates both total particles and viable particles in the air. Cleanroom and sterility test materials, such as sterile gowns, paper, Tryptic soy broth and sterile silicone, were evaluated for their ability to produce a false positive response under certain conditions. Recommendations for reducing or eliminating the potential for false positives when using these materials were also provided.