Pos0706 Clinical Usefulness of Polymerase Chain Reaction-Lateral Flow for the Diagnosis and Management of Periprosthetic Joint Infections in Rheumatoid Arthritis Patients at Risk for Bacterial Culture-Negative

Background: Periprosthetic joint infections (PJIs) with bacterial culture-negative results are challenging to diagnose and manage. Biomarkers such as C-reactive protein and alpha-defensin are often reported to be elevated in patients with inflammatory rheumatic diseases. Therefore, it is difficult to judge whether elevations in biomarkers are caused by infection or flare of a rheumatic disease. To increase the sensitivity of detecting causative microorganisms, a number of methods, including polymerase chain reaction (PCR), have been reported. PCR-lateral flow can detect methicillin-resistant Staphylococcus aureus (MRSA), methicillin-sensitive S. aureus (MSSA), and methicillin-resistant coagulase-negative Staphylococcus (MR-CNS). In the clinical setting, we routinely use PCR-lateral flow for the diagnosis of PJI in patients with rheumatoid arthritis at risk for culture-negative infections, such as patients with prior antimicrobial therapy or patients with documented negative results from prior or present bacterial cultures. Objectives: To clarify the clinical usefulness of PCR-lateral flow for the diagnosis and management of PJI in patients with rheumatoid arthritis at risk for culture-negative infections. Methods: This retrospective study included suspected cases of PJI between 2018 and 2023 at our institution. Diagnosis of PJI was determined based on the entire clinical course by two rheumasurgeons. Using genomic DNA isolated from synovial fluid or soft tissues, multiplex PCR was performed with two genetic markers: the S. aureus-specific gene femA and the antibiotic resistant gene mecA. PCR products were qualitatively assessed using the lateral flow method. PCR-lateral flow results, demographics, laboratory and culture findings, and clinically diagnosis of PJI were investigated. Results: This analysis included 18 episodes in 16 patients (13 females and 3 males; average age, 77 years). There were 5 (28%) bacterial culture-positive episodes and 13 (78%) culture-negative episodes. PJI was clinically diagnosed in 13 episodes. The sensitivity of bacterial culture and PCR-lateral flow was 38% and 38%, respectively. Five episodes without infection had both negative bacterial culture and PCR-lateral flow results; the final diagnoses were flare of rheumatoid arthritis (n = 3), pseudogout attack (n = 1), and aseptic loosening (n = 1). Among 8 PJI episodes with bacterial culture-negative results, 4 episodes were identified as MR-CNS (n = 3) or MSSA (n = 1) based on PCR-lateral flow. PCR-lateral flow results were consistent with the clinical course and antimicrobial responsiveness. Conclusion: The PCR- lateral flow method can identify false-negative bacterial cultures and provide useful information for the diagnosis and management of PJI in patients with rheumatoid arthritis at risk for bacterial culture-negative infections. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.