Detecting the presence of bacteria in low-volume preoperative aspirated synovial fluid by metagenomic next-generation sequencing

•The preoperative synovial fluid volume used for mNGS analysis was only 1 ml, so it does not conflict with the microbial culture process.•mNGS can improve PJI diagnosis of cases with low-volume preoperative aspirated synovial fluid compared with synovial fluid culture.•mNGS was recommended as an effective supplemental diagnostic tool to improve PJI diagnosis preoperatively. Preoperative diagnosis is important for patients who need revision surgery due to PJI. Microbial culture plays an important role in PJI diagnosis, but the sensitivity of cultures is low when the sample amount is limited or when a patient is treated with antibiotics before sample collection. In this study, metagenomic next-generation sequencing (mNGS) was used to detect bacteria in preoperative puncture synovial fluid samples from patients with suspected PJI, and the preoperative and intraoperative culture results were compared to estimate its diagnostic efficiency. From July 2016 to December 2018, patients with suspected PJI who underwent prosthetic joint revision surgery were included, and the results of those who had been tested by preoperative synovial fluid culture and mNGS were obtained. The demographic characteristics, medical history, laboratory test results, culture results, and mNGS results of each patient were recorded. Then, the efficiency of preoperative synovial fluid mNGS was compared to that of synovial fluid culture for diagnosing PJI. A total of 37 patients were included, and 24 patients (25 joints) were diagnosed with PJI. The sensitivity, specificity, and accuracy of preoperative synovial fluid mNGS were 92%, 91.7%, and 83.7%, respectively. The sensitivity, specificity, and accuracy of preoperative synovial fluid culture were 52%, 91.7%, and 43.7%, respectively. With a low volume of synovia (1 ml), mNGS can be performed with higher sensitivity and specificity compared to synovial culture. Thus, mNGS can be a useful supplemental method to improve diagnostic efficiency during the preoperative period.