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The alpha-defensin test for periprosthetic joint infection outperforms the leukocyte esterase test strip
Carl Deirmengian1, Keith Kardos, Patrick Kilmartin
1CD Diagnostics Inc, Lankenau Institute for Medical Research, The Rothman Institute, 100 Lancaster Avenue, MOB 456, Wynnewood, PA, 19096, USA.
Background:
Synovial fluid biomarkers have demonstrated 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 α-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 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.
Results:
The 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%.
Conclusions:
The 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 Evidence:
Level II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.
Insights
The synovial fluid α-defensin immunoassay shows 100% sensitivity and specificity for diagnosing periprosthetic joint infection (PJI), outperforming the leukocyte esterase test strip.
Area of Science:
- Orthopedic surgery
- Infectious disease diagnostics
- Biomarker research
Background:
- Synovial fluid biomarkers offer superior diagnostic accuracy for periprosthetic joint infection (PJI) compared to current methods.
- The need for reliable and accurate diagnostic tools for PJI is critical in orthopedic surgery.
Purpose of the Study:
- To directly compare the diagnostic performance of synovial fluid α-defensin immunoassay against the leukocyte esterase (LE) colorimetric test strip for PJI.
- To evaluate the sensitivity and specificity of these two diagnostic methods in a prospective study.
Main Methods:
- Prospective collection of synovial fluid from 46 patients undergoing joint replacement surgery.
- Testing of synovial fluid samples using a novel α-defensin immunoassay and a leukocyte esterase (LE) colorimetric test strip.
- Classification of patients into periprosthetic infection (23 cases) or aseptic failure (23 cases) groups based on the Musculoskeletal Infection Society (MSIS) definition as the gold standard.
Main Results:
- The α-defensin immunoassay achieved 100% sensitivity and 100% specificity in diagnosing PJI, correctly classifying all 46 patients.
- The α-defensin assay provided reliable results even in samples with blood contamination.
- The LE test strip showed 69% sensitivity and 100% specificity but was uninterpretable in 17% of samples due to blood interference.
Conclusions:
- The synovial fluid α-defensin immunoassay is a highly accurate and reliable diagnostic tool for PJI, outperforming the LE colorimetric test strip.
- The α-defensin immunoassay offers simpler interpretation and is unaffected by blood, making it a more attractive option for diagnosing PJI.
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