Diagnostic accuracy of the alpha-defensin lateral flow test in periprosthetic shoulder infection: a retrospective study

Background: The aim of this study is to assess the diagnostic value of the alpha (α)-defensin lateral flow (ADLF) test in a group of patients with suspected shoulder periprosthetic joint infections (PJIs) and its usefulness and correlation with other diagnostic tests in the decision-making process. Methods: This retrospective single-center study was conducted between 2018 and 2023. Alpha -defensin was measured using an ADLF test kit. The final diagnosis of shoulder PJI was confirmed or ruled out based on the Musculoskeletal Infection Society criteria. Results: After selecting patients based on the exclusion criteria, the final study group comprised 22 patients. Of all patients, the test was positive in five cases. The ADLF test was false-positive in two patients and was false-negative in zero patients. The test was truly negative in 17 cases, resulting in a sensitivity of 100.00% (95% CI, 100.00%–100.00%) and a specificity of 89.47% (95% CI, 76.65%–102.3%). The positive predictive value was 60.00% (95% CI, 39.53%–80.47%) and the negative predictive value was 100.00% (95% CI, 100.00%–100.00%). The accuracy of the α-defensin test was found to be 90.9%. Conclusions: Although this study has limitations such as small sample size and research design, the ADLF test has proven to be a useful diagnostic tool. It can serve as a supplement to traditional tests, providing additional support to orthopedic surgeons in both preoperative and intraoperative diagnosis, especially in its ability to exclude the possibility of a PJI. Level of evidence: III.