False-negative synovial alpha-defensin

We present a case of chronic periprosthetic hip infection diagnosed using the Musculoskeletal Infection Society criteria as the gold standard. The alpha-defensin test was falsely negative. The diagnostic workup of the patient is detailed, along with a discussion regarding the potential reasons behind the misleading alpha-defensin results. To our knowledge, this is the first reported case of a false-negative alpha-defensin test in the setting of an open sinus tract communicating with a culture-positive total hip implant. The alpha-defensin test should be interpreted cautiously, along with all relevant pertinent clinical data. In certain cases, similar to those described here, the Musculoskeletal Infection Society criteria may perform better than this particular biomarker.