Rapid molecular culture versus conventional culture for periprosthetic joint infection: diagnostic performance and clinical relevance

Introduction: Periprosthetic joint infection (PJI) remains a major complication of joint arthroplasty, requiring rapid and accurate pathogen identification to guide appropriate antimicrobial therapy. Conventional culture is limited by prolonged turnaround times and reduced sensitivity, particularly following antibiotic exposure. This study evaluated the diagnostic performance and clinical relevance of Molecular Culture (R) (MC), a rapid PCR-based assay, using sonication fluid (SF) obtained during revision arthroplasty. Methods: SF samples from patients undergoing hip or knee revision arthroplasty (2019-2023) were retrospectively analysed. Patients were classified as PJI or non-PJI according to European Bone and Joint Infection Society criteria. MC results were compared with conventional SF culture. Positive percentage agreement (PPA) and negative percentage agreement (NPA) were calculated using culture as the reference standard. Clinical agreement was assessed using all available microbiological results and relevant clinical information, including recent antibiotic exposure. Results: A total of 203 SF samples from 172 patients were included. Analytical PPA and NPA of MC were 68.1 % (95 % CI, 59.9-75.3) and 84.6 % (95 % CI, 73.9-91.4), respectively. Following clinical correlation, PPA and NPA at patient level were 73.2 % (95 % CI, 64.9-80.2) and 95.6 % (95 % CI, 85.2-98.8), respectively. MC identified 11 additional clinically relevant pathogens and provided results within approximately 4 h. Conclusions: MC demonstrated high clinically adjusted agreement and faster turnaround times than conventional culture, supporting its role as an adjunctive diagnostic tool for PJI. Its value may be greatest in patients with uncertain infection status or prior antimicrobial exposure, where rapid exclusion of infection could facilitate earlier optimisation of antimicrobial therapy.