Alpha defensin accuracy and pitfalls in diagnosing septic arthritis in native joints

Abstract

Purpose: This study aimed to test the accuracy of the synovial fluid biomarker, α-defensin, in diagnosing septic arthritis in native joints and highlight the pitfalls of its utilization for primary joints. We also discuss the cases where false results were demonstrated.

Methods: A retrospective review of 10 patient’s records, who underwent α-defensin testing for suspected primary joint infections prior to performing arthroplasty surgery, was performed.

Results: 6 primary knee and 4 primary hip joints were evaluated for septic arthritis utilizing the α-defensin test after arthrotomy was performed, as the patient had turbid synovial fluid or atypical bony features suggestive of septic arthritis. 2 of the primary hip joints had previous cephalomedullary nail insertions that cut-out and 1 knee joint had previous distal femur fixation for peri-articular fracture. There were 2 false positive α-defensin results in native knee joints that were eventually attributed to inflammatory arthritis after extensive cultures and microbial sequencing results returned negative. All other patients had negative α-defensin results that correlated with anti- microbial testing.

Conclusion: The utilisation of the α-defensin test in primary joints should be interpreted with caution. The elevated levels of α-defensin may be attributable to inflammatory arthritis and further studies of its levels in native joints are required.