RAPID NOVEL MOLECULAR METHOD FOR ENHANCED DETECTION OF PERIPROSTHETIC JOINT INFECTION

Aim Standard culture for diagnosing periprosthetic joint infection (PJI) requires 10-14 days of incubation and may fail to detect pathogens, particularly after prior antibiotic exposure. Rapid molecular methods such as interspace profiling (IS-pro) may substantially shorten both time to diagnosis and time to definitive treatment, while potentially improving diagnostic sensitivity. We evaluated the performance of IS-pro on sonication fluid (SF) against routine culture. Methods SF samples (n=201) from prosthetic joint material of 148 PJI and 28 non-PJI patients were retrospectively analysed using IS-pro 1 with proprietary Antoni software. For certain species, IS-pro reports equivalent sets where no distinction can be made between two species. Positive percentage agreement (PPA) and negative percentage agreement (NPA) was calculated. Analytical agreement with conventional culture was assessed on sample level, followed by clinical agreement on patient level, incorporating data on previous antibiotic exposure and culture results of all other intraoperative samples (tissues and synovial fluid), as well as earlier microbiological findings. Results Median time to culture positivity was 3 days (range: 1–16), whereas IS-pro including interpretation required 6-8 hours. Analytical PPA and NPA were 66.7% (95% CI 58.4-74.0) and 84.6% (95% CI 73.1-91.4), respectively. When incorporating microbiological results from additional sample types and data on prior antibiotic exposure, clinical PPA and NPA were 73.3% (95% CI 64.9-80.2) and 95.6% (95% CI 85.2-98.8), respectively. IS-pro results suggested that three culture-positive and seven culture-negative cases might have benefited from alternative antibiotic treatment. Out of these 10 patients, four had received antibiotics in the two weeks prior to surgery. Conclusions IS-pro provides clear clinical value by markedly reducing turnaround time and improving pathogen detection, particularly in patients with prior antibiotic exposure and negative cultures. These findings support its use not only as an adjunct to conventional diagnostics, but also as a potential first-line screening method for rapid pathogen identification in suspected PJI. A prospective study including parallel analysis of intraoperative tissue and synovial fluid samples is planned to further validate its diagnostic performance.