The primary objective of this study is to demonstrate the validity of the Microbial- ID test to aid in diagnosis of periprosthetic joint infection (PJI) in terms of sensitivity and specificity.

In the diagnosis of periprosthetic joint infection (PJI) there is no golden standard test. Multiple definitions for the diagnosis of PJI exist, such as the European Bone and Joint Infection Society (EBJIS)1, Musculoskeletal Infection Society (MSIS)2, and the Infectious Diseases Society of America (IDSA)3. One of the criteria that defines PJI is that there are at least two positive periprosthetic cultures with phenotypically identical organisms. Although these two positive bacterial cultures can certainly be considered proof of PJI, many other criteria are also used, such as a sinus tract, white blood count (WBC), elevated C-reactive protein and/or erythrocyte sedimentation rate (ESR), elevated percentage of neutrophils, and positive alpha defensin. Even when all these criteria are negative, a PJI cannot be excluded. Zimmer Biomet developed the Synovasure® Microbial-ID test that enables early and faster identification of microbial species through detection of microbial antigens responsible for infection.

This is an international multicenter, non-randomized, prospective, non-intervention clinical investigation.The primary objective of this study is to demonstrate the validity of the Microbial-ID test to aid in diagnosis of PJI in terms of sensitivity and specificity. The study population is adult patients with a potentially infected joint implant, who will undergo an articular puncture and/or surgery with harvesting of synovial fluid. In addition to the standard of care procedure for patients with a suspected PJI, the MID-test will be performed using the residual synovial fluid. Individual test results of the MID-test are not reported back to the participating sites in order to not interfere with the sites' standard of care approach.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Patients do not benefit from participating in this study. A separate diagnostic tool will run in parallel but this procedure will not interfere with the patient's current path of diagnostic work up nor will it have an effect on their treatment plan. The results will help the investigators to get more insight in the reliability of the MID-test to detect microbial antigens responsible for the PJI. There are no known disadvantages for the patients taking part in this research.

Inclusion Criteria:

• Patient has complaints (pain, stiffness) about the prosthetic joint And has clinical features for joint infection at physical examination (swelling, redness, warm, sinus tract) AND has an elevated serum CRP (>10 mg/L)
• Patient is scheduled for a puncture AND/OR surgery, with harvesting of synovial fluid
• Patient ≥ 18 years of age
• Patient is competent, able, and willing to provide written informed consent

Exclusion Criteria:

• Treatment with antibiotics ≤2 weeks prior to puncture and/or surgery;
• Other obvious reason(s) for implant dysfunction, such as: fracture, an implant breakage, a malposition, and/or a tumour.

Adult patients with a potentially infected joint implant, who will undergo an articular puncture and/or surgery with harvesting of synovial fluid.