BEYOND INDICATIONS: REAL-WORLD PERFORMANCE OF MULTIPLEX PCR IN NON-SYNOVIAL MUSCULOSKELETAL INFECTIONS

Aim Multiplex PCR-based joint infection panels enable rapid pathogen identification but are validated only for synovial fluid. Their real-world performance in non-synovial musculoskeletal infections remains poorly defined. This study aims to evaluate the diagnostic performance, concordance with culture, and clinical implications of off-label multiplex PCR* use in musculoskeletal infections. Methods A retrospective study was conducted at a tertiary multidisciplinary bone infection unit between May 2023 and May 2025. Consecutive patients undergoing surgical debridement with non-synovial samples analysed using a multiplex PCR joint infection panel were included. All cases underwent parallel conventional microbiology, including aerobic, anaerobic, mycobacterial, and fungal cultures. Outcomes included concordance with culture, discordance patterns, organism spectrum, and diagnostic yield across infection types. Results 80 non-synovial samples were analysed across fracture-related infection (n=31), soft tissue infection (n=24), hematogenous osteomyelitis (n=11), diabetic foot infection (n=9), and spinal implant-related infection (n=4). Concordance between PCR and culture ranged from 36–50% and was lowest in diabetic foot infection (22.2%), reflecting polymicrobial complexity. Discordance was frequent (up to 66.7%), predominantly due to detection of additional organisms by PCR in polymicrobial infections. Anaerobes and low-abundance organisms were frequently detected by PCR but not recovered on culture. Conversely, culture identified clinically significant off-panel organisms in 17 cases, including non-fermenting Gram-negatives, mycobacteria, and fungi. PCR provided rapid results (~1 hour vs several days for culture). Conclusion Multiplex PCR demonstrates clinically meaningful utility in non-synovial musculoskeletal infections, particularly through enhanced detection of polymicrobial and anaerobic disease. However, frequent discordance and the presence of off-panel organisms necessitate a complementary diagnostic strategy. PCR supports early decision-making, while culture remains essential for comprehensive pathogen detection and antimicrobial susceptibility testing. Careful integration into diagnostic pathways is critical when extending use beyond validated indications. *Brand Name: BIOFIRE® Joint Infection Panel