Microbial Next Generation DNA Sequencing of Aspirated Synovial Fluid Shows Concordance with ICM Criteria Biomarkers for Diagnosing Periprosthetic Joint Infection in Hip and Knee Arthroplasty

Background The diagnosis of periprosthetic joint infection (PJI) is facilitated by consensus identification of synovial biomarkers, which may be aided by targeted microbial next generation sequencing (NGS) of synovial fluid. The primary objective of the study was to evaluate NGS performance across 3 years to ICM 2018 minor criteria for PJI. Methods Synovial fluid specimens submitted from 2020–2022 by outpatient surgical clinics to MicroGenDX for matched synovial biomarker and NGS analysis were selected for retrospective analysis. Synovial biomarkers tested included C-reactive protein (CRP), white blood cell (WBC) count, and polymorphonuclear (PMN) leukocyte percentage. Synovial fluid analysis compared NGS microbial positivity with positive incidence of PJI determined by scoring of synovial biomarkers using ICM 2018 minor criteria for infection. Results The overall sensitivity, specificity, and accuracy of NGS to ICM diagnosed PJI across 2,011 specimens was 76.4% [95% CI: 0.723–0.801], 92.3% [0.91–0.94], and 88.7% [0.87–0.90], respectively. When comparing the diagnostic performance of NGS and individual biomarkers to infection, NGS was more specific to PJI than synovial CRP (specificity = 0.894, 95% CI: 0.88–0.91), but not PMN or WBC. NGS was positive in 7.7% of ICM negative samples. NGS positive:ICM negative samples were associated with significantly elevated synovial PMN (p = 0.001) and WBC (p < 0.0001) compared to NGS negative:ICM negative samples. Across all samples, NGS positivity was associated with significantly elevated results for all tested biomarkers (p < 0.0001). Eight bacterial species dominated the composition in 68% of samples, whereas 46 different microbes were dominant in the remaining third. Conclusions Microbial targeted NGS positivity was concordant with ICM minor criteria for PJI and should be considered a useful tool for diagnosis. There is a low risk of false positive detections comparable to ICM biomarkers. Elevated biomarkers in NGS positive:ICM negative samples may indicate infection occurring that is poorly captured by the three measured synovial biomarkers. Uncommon species are collectively common to PJI and NGS is uniquely positioned to detect such species as they are frequently missed by conventional microbiological testing, including culture and quantitative PCR. These results suggest formal diagnostic schemes would benefit from the addition of NGS as a diagnostic criterion.