Lack of Diagnostic Value from Fungal and Mycobacterial Cultures in Cases of Suspected Prosthetic Joint Infection

Abstract Introduction/Objective Infections of prosthetic joints cause significant morbidity and often result in removal of the infected joint. In many cases, an infectious etiology can be difficult to definitively identify. As a result, providers suspecting prosthetic joint infections (PJI) often place large order sets of microbiology tests, including fungal and mycobacterial cultures. Fungal and mycobacterial cultures are labor-intensive for the laboratory taking up to 28 days and 42 days, respectively, to complete. As a potential area for a diagnostic stewardship intervention, we wanted to evaluate how often a fungal or mycobacterial culture produced actionable information in cases of suspected PJI. Methods/Case Report Data reports were retrieved from both the Electronic Health Record (EHR) and the Laboratory Information System (LIS) from May 2022 to May 2023. As sources submitted by the provider often do not specify that the joint is prosthetic, data from LIS was evaluated to identify microbiology culture test sets ordered on joint sources, while data from EHR was examined to isolate patients with implanted joints. Using Microsoft Excel, data from both systems was compared in order to match microbiology culture test sets to the known implanted joints. LIS data from implanted joint sources was assessed to record negative (no growth) and positive (growth) cultures, and to register all organisms isolated. Results (if a Case Study enter NA) Of 794 order sets for cultures collected from prosthetic joint sources, 430 included requests for fungal culture and 79 included requests for mycobacterial culture. Of these 79 requests for mycobacterial culture, 0 organisms were isolated (0%). Of these 430 requests for fungal culture, 7 grew yeast (1.6%) and 7 out of 7 (100%) of these yeasts were also isolated on general (aerobic bacterial) culture. No molds were isolated. Conclusion Discontinuing the routine practice of ordering fungal and mycobacterial culture for prosthetic joint sources would have no negative impact on patient care but would reduce unnecessary work in the microbiology laboratory and potentially avoid additional costs to the patient. Education to the orthopedic provider group as well as best practice alerts in the EHR will be pursued, based on the findings from this study, in order to reduce unnecessary culture orders.