Low sensitivity of a-defensin (Synovasure) test for intra­operative exclusion of prosthetic joint infection

Abstract

Background and purposeThe Synovasure lateral flow test was developed as a rapid test for the detection or exclusion of periprosthetic joint infection (PJI). 3 studies have reported promising results on its diagnostic value in total joint revision surgery. We aimed to assess the sensitivity and specificity of the Synovasure test to exclude infection in patients undergoing revision surgery for suspected early aseptic loosening of a total hip or knee arthroplasty.Patients and methodsIn a prospective study design, 37 patients who underwent revision surgery for suspected early aseptic loosening (< 3 years after primary arthroplasty) were included. The Synovasure test was used intraoperatively to confirm the aseptic nature of the loosening and 6 tissue cultures were obtained in all cases. Exclusion criteria were patients with a preoperatively confirmed PJI, acute revisions (< 90 days after primary arthroplasty) and cases with malpositioning, wear, or instability of the prosthesis.Results5 of the 37 patients were diagnosed with a PJI based on the intraoperative tissue cultures. In only 1 out of these 5 cases this was confirmed by the intraoperative Synovasure test. No tests were falsely positive.InterpretationIn this case series the Synovasure lateral flow test had a low sensitivity to exclude PJI in patients with suspected aseptic loosening. The role of the Synovasure lateral flow test in the intraoperative exclusion of PJI during revision surgery for suspected early aseptic loosening appears to be more limited than previously indicated.

High-Performance Liquid Chromatography as a Novel Method for the Determination of α-Defensins in Synovial Fluid for Diagnosis of Orthopedic Infections

“…In our practice, we also have noticed that the results of the test are not reliable in cases of acute PJI, especially due to the occurrence of false negative findings. False negative results of the Synovasure ® lateral flow method in PJI may be also due to the occurrence of low-virulence bacterial strains (e.g., Staphylococcus epidermidis and Propionibacterium acnes), as reported by Scholten et al [21]. In their work, five of 37 patients were diagnosed with PJI based on the intraoperative tissue cultures, but the Synovasure ® test confirmed the infection in only one of these five cases.…”

“…The test seemed much more beneficial than the more commonly used screening methods (cultivation, histology, PCR, leukocyte esterase, and others). Recently, however, debate has arisen over this method's accuracy [14,20,21]. This concern has been focused primarily on the results of studies that questioned the benefit of determining AD from synovial fluid, where, in particular, sensitivity was lower and varied in comparison with previous results.…”

“…This concern has been focused primarily on the results of studies that questioned the benefit of determining AD from synovial fluid, where, in particular, sensitivity was lower and varied in comparison with previous results. For the lateral flow method, sensitivity is between 67% and 100% and specificity 94% to 97% [11,12,16,21].…”

Current Clinical Methods for Detection of Peri-Prosthetic Joint Infection

“…When combined with culturing, sensitivity and specificity reach 96% and 100%, respectively [57]. Alpha defensin may miss infections with low-virulence organisms such as coagulase negative CoNS or C. acnes, with up to an 80% false negative rate [21,58].…”

“…Synovial levels of alpha defensin are unaffected by recent antibiotic therapy in patients [56,58], giving it an advantage over biomarkers such as CRP [43]. Synovasure ADLF showed statistical improvement over MSIS minor criteria including ESR/CRP level, pre-operative culture (1 positive), and synovial cell count [23,60].…”