Diagnosis of Spinal Infection with Alpha-defensin Lateral Flow Test: A Preliminary Report

Introduction: The alpha-defensin lateral flow test has been used in periprosthetic joint infection as a diagnostic support tool because of its simplicity and speed. However, the test has not been used to diagnose spinal infections. The purpose of this study was to investigate the efficacy of the alpha-defensin lateral flow test for diagnosing spinal infections.Methods: The subjects were 11 patients who were suspected of having spinal infections from October 2019 to August 2021 and underwent biopsies at a single institution. There were nine male and two female patients, with an average age of 60.7 (14-87) years. For diagnosing infection, the patient's consent for biopsy was obtained, and the sample was collected by computed tomography-guided aspiration biopsy or open biopsy at the site considered to be a possible abscess. The samples were subjected to a bacterial culture test, an acid-fast bacillus culture test, and an alpha-defensin lateral flow test (Synovasure® lateral flow test; Zimmer Biomet, IN, USA).Results: Of the 11 suspected spinal infections, the alpha-defensin lateral flow test was positive in 8 cases, negative in 2 cases, and undeterminable in 1 case. Of the 10 cases excluding the undeterminable case, the definitive diagnosis was 9 cases of spinal infection (spondylitis: 6 cases, spinal implant infection: 3 cases) and 1 case of vertebral body fracture. The alpha-defensin lateral flow test demonstrated a sensitivity of 88.9%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 50%. The biopsy sample culture test demonstrated a sensitivity of 77.8%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 33.3%.Conclusions: We suggested that the alpha-defensin lateral flow test might be useful as a diagnostic support tool for spinal infections.