The Alpha-defensin Test for Periprosthetic Joint Infection Outperforms the Leukocyte Esterase Test Strip

Abstract

BackgroundSynovial fluid biomarkers have demonstrated diagnostic accuracy surpassing the currently used diagnostic tests for periprosthetic joint infection (PJI).Questions/purposesThe purpose of this study is to directly compare the sensitivity and specificity of the synovial fluid α-defensin immunoassay to the leukocyte esterase (LE) colorimetric test strip.MethodsSynovial 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 α-defensin and the LE colorimetric test strip. The Musculoskeletal Infection Society (MSIS) definition was used to classify 23 periprosthetic infections and 23 aseptic failures; this classification was used as the standard against which the two diagnostic tests were compared.ResultsThe synovial fluid α-defensin immunoassay correctly predicted the MSIS classification of all patients in the study, demonstrating a sensitivity and specificity of 100% for the diagnosis of PJI. The α-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%.ConclusionsThe synovial fluid α-defensin immunoassay outperformed the LE colorimetric test strip in this study and provided reliable results even when the LE test strip failed as a result of blood interference. The simple analytic results provided by the α-defensin immunoassay, compared with the more complex and interpretive nature of both the MSIS criteria and LE colorimetric test strip, make it a highly attractive diagnostic tool.Level of EvidenceLevel II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

The Alpha Defensin-1 Biomarker Assay can be Used to Evaluate the Potentially Infected Total Joint Arthroplasty

“…The results of the AD-1 assay had excellent sensitivity and specificity and were consistent with previously reported data [3]. The current study is the first independent study, to our knowledge, to confirm that the AD-1 can be used for workup and diagnosis of a PJI.…”

The Alpha-Defensin Immunoassay and Leukocyte Esterase Colorimetric Strip Test for the Diagnosis of Periprosthetic Infection

“…Advantages of this test are that it is quick, easy, and inexpensive at £0.11 (US$0.17) per test (Chemstrip 7; Roche Diagnostics). A potential disadvantage is the invalidation of the result by blood contamination 17 , although this has been addressed by centrifugation prior to application of the fluid…”

“…MSIS = Musculoskeletal Infection Society, PJI = periprosthetic joint infection, ESR = erythrocyte sedimentation rate, CRP = C-reactive protein, and WBC = white blood cell, and HPF = high-power field. Sensitivity and specificity of alpha-defensin in the diagnosis of PJI, according to Deirmengian et al 17 , Deirmengian et al 27 , Bingham et al 26 , and…”

“…here were 10 articles reporting 11 evaluations 13,14,17,18,[26][27][28][29][30][31] that contributed to our estimates of diagnostic accuracy for both tests. Six studies explored the diagnostic accuracy of alpha-defensin for PJI 13,17,[26][27][28]31 , while the remaining 5 studies explored the diagnostic accuracy of leukocyte esterase for PJI 14,17,18,29,30 .…”

“…Six studies explored the diagnostic accuracy of alpha-defensin for PJI 13,17,[26][27][28]31 , while the remaining 5 studies explored the diagnostic accuracy of leukocyte esterase for PJI 14,17,18,29,30 . Study characteristics are summarized in Table III. All of the included studies were published within the last 5 years and originated from the U.S.…”