(Management Case Study) Pharmacy and Laboratory Collaboration to Update Minimum Inhibitory Concentration (MIC) Susceptibility Breakpoints and Interpretations

Purpose: Increasing antimicrobial resistance has led to more frequent updates of minimum inhibitory concentration (MIC) susceptibility breakpoints for specific microorganism-antibiotic combinations.  Utilization of updated MIC susceptibility breakpoints can be delayed since commercial manufacturers of antimicrobial susceptibility testing (AST) instruments are not required by the Food and Drug Administration (FDA) to update breakpoints, but when updated, FDA approval is required.  This case describes how pharmacy and laboratory department collaboration led to optimization in utilizing updated MIC susceptibility breakpoints and interpretations even though a hospital AST instrument was not employing all breakpoint updates.

Methods: The lead antimicrobial stewardship (AS) pharmacist identified an opportunity to move from a manual pharmacy review to an automated microbiology process to ensure updated MIC breakpoints were utilized for interpretation of antibiotic susceptibilities. The AS pharmacist then worked with the microbiology laboratory supervisor to provide literature for implementation considerations and to ensure feasibility of the process changes.  The two hospital departments determined that Clinical Laboratory Standards Institute (CLSI) MIC susceptibility breakpoints would be utilized instead of FDA breakpoints.  The microbiology process change was presented to the inter-disciplinary AS committee which included representatives from medicine, pharmacy, nursing, laboratory, infectious diseases, infection prevention, quality, information technology, education, and administration.  Acquisition of new rapid diagnostic equipment for the process change was justified due to the inability to optimize current instruments to implement susceptibility breakpoint updates.  Examples of how the rapid diagnostic instrument could positively impact other AS efforts were also presented.  After the AS committee recommended to incorporate the process changes, the laboratory director confirmed with hospital administration that the addition of new equipment would not increase ongoing costs and would allow for more streamlined microorganism identification by laboratory personnel.  The collaborating departments emphasized that the plan, do, check, and act (PDCA) cycle would be required to ensure the AST instrument software, electronic health record (EHR), and microbiology laboratory processes were working appropriately to provide updated breakpoint interpretations.

Results: Hospital administration approved the purchase of a new rapid diagnostic instrument and updated AST instrument based on the AS committee recommendation to integrate automated CLSI susceptibility breakpoint updates.  Prior to instrument implementation, microbiology reviewed CLSI guidelines for quality assurance requirements for off-label AST instrument validation for updated MIC susceptibility breakpoints.  Pharmacy and the infectious diseases physician reviewed and selected the most appropriate microbiology panels for the hospital laboratory.  Lastly, microbiology obtained microorganisms from the Centers for Disease Control and Prevention and FDA Antibiotic Resistance Isolate Bank to complete the validation process.  After validation of specific updated microorganism-antibiotic MIC breakpoints and susceptibility interpretations was completed, pharmacy and microbiology continued to apply the PDCA cycle. Solutions for AST instrument software limitations were determined for susceptible dose-dependent interpretations and when different MIC breakpoints existed for the same microorganism-antibiotic combination based on specimen source.  The PDCA cycle was also applied to address previously developed AST instrument susceptibility suppression rules and to create more robust resistance nomenclature within reported organism names.

Conclusion: Pharmacy and laboratory collaboration and implementation of the PDCA cycle led to improvements in microbiology antimicrobial stewardship efforts with updated MIC susceptibility breakpoints and interpretations.