SYMPOSIUM: 2014 KNEE SOCIETY PROCEEDINGS The Alpha-defensin Test for Periprosthetic Joint Infection Outperforms the Leukocyte Esterase Test Strip

The Author(s) 2014. This article is published with open access at Springerlink.com Background Synovial fluid biomarkers have demon-strated diagnostic accuracy surpassing the currently used diagnostic tests for periprosthetic joint infection (PJI). Questions/purposes The purpose of this study is to directly compare the sensitivity and specificity of the synovial fluid a-defensin immunoassay to the leukocyte esterase (LE) colorimetric test strip. Methods Synovial fluid was collected from 46 patients meeting the inclusion criteria of this prospective diagnostic study. Synovial fluid samples were tested with both a novel synovial-fluid-optimized immunoassay for a-defensin and the LE colorimetric test strip. The Musculoskeletal Infec-tion Society (MSIS) definition was used to classify 23 periprosthetic infections and 23 aseptic failures; this clas-sification was used as the standard against which the two diagnostic tests were compared. Results The synovial fluid a-defensin immunoassay cor-rectly predicted the MSIS classification of all patients in the study, demonstrating a sensitivity and specificity of 100 % for the diagnosis of PJI. The a-defensin assay could be read for all samples, including those with blood in the synovial fluid. The leukocyte esterase test strip could not be interpreted in eight of 46 samples (17%) as a result of blood interference. Analysis of the LE strips that could be interpreted yielded a sensitivity of 69 % and a specificity of 100%. The institution of one or more of the authors (CD, JP) has received, during the study period, funding from CD Diagnostics (Wynnewood