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Validation of the Alpha Defensin Lateral Flow Test for Periprosthetic Joint Infection
Carl Deirmengian1,2, John Madigan2, Sujith Kallur Mallikarjuna2
1Department of Orthopaedic Surgery, Rothman Orthopaedic Institute, Lankenau Institute for Medical Research, Wynnewood, Pennsylvania.
Background:
The synovial fluid test for alpha defensin has been reported to have an excellent performance in diagnosing periprosthetic joint infection (PJI). The purpose of this study was to evaluate the performance of the lateral flow test for synovial fluid alpha defensin by using the methods of a formal diagnostic accuracy study and to compare its performance with that of the laboratory-based alpha defensin test for PJI.
Methods:
We conducted a diagnostic accuracy study of the index lateral flow immunoassay for synovial fluid alpha defensin relative to the reference 2013 Musculoskeletal Infection Society (MSIS) multicriteria definition of PJI. The study included a prospective multicenter cohort of outpatients with a failed hip or knee arthroplasty and a supplemental control cohort of fresh synovial fluid specimens submitted by physicians for diagnostic PJI testing.
Results:
Among 57 patients with PJI and 248 patients without PJI in the overall prospective patient cohort, the sensitivity and specificity of the alpha defensin lateral flow test were 89.5% (95% confidence interval [CI]: 78.5% to 96.0%) and 94.8% (95% CI: 91.2% to 97.2%), respectively. The sensitivity increased to 94.3% (95% CI: 84.3% to 98.8%) after exclusion of 17 patients with grossly bloody aspirates (>1 million red blood cells/µL). Among the supplemental control cohort of fresh synovial fluid samples, including 65 samples from patients with PJI and 397 from patients without PJI, the sensitivity and specificity of the alpha defensin lateral flow test were 98.5% (95% CI: 91.7% to 100.0%) and 98.2% (95% CI: 96.4% to 99.3%), respectively. A comparison of the sensitivity and specificity of the alpha defensin lateral flow test with those of the alpha defensin enzyme-linked immunosorbent assay (ELISA) in the combined cohort did not demonstrate a significant difference in sensitivity (94.3% [95% CI: 88.5% to 97.7%] compared with 93.0% [95% CI: 87.1% to 96.7%]) or specificity (96.9% [95% CI: 95.3% to 98.1%] compared with 97.8% [95% CI: 96.4% to 98.8%]) (both p > 0.05).
Conclusions:
The results of this study demonstrate the solid diagnostic performance of the alpha defensin test and have resulted in the U.S. Food and Drug Administration (FDA) authorization of the lateral-flow test with an intended use as an aid in the clinical diagnosis of PJI.
Level Of Evidence:
Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.
Insights
The alpha defensin lateral flow test shows excellent performance in diagnosing periprosthetic joint infection (PJI). This diagnostic accuracy study confirms its reliability, leading to FDA authorization as a PJI diagnostic aid.
Area of Science:
- Orthopedics
- Infectious Diseases
- Diagnostic Medicine
Background:
- Periprosthetic joint infection (PJI) diagnosis relies on accurate testing.
- Synovial fluid alpha defensin tests have shown promise for PJI detection.
Purpose of the Study:
- To evaluate the diagnostic accuracy of a novel lateral flow test for synovial fluid alpha defensin.
- To compare the lateral flow test's performance against a laboratory-based alpha defensin test for PJI.
Main Methods:
- A diagnostic accuracy study was conducted using a prospective multicenter cohort and a supplemental control cohort.
- The index test was a lateral flow immunoassay for synovial fluid alpha defensin.
- The reference standard was the 2013 Musculoskeletal Infection Society (MSIS) multicriteria definition of PJI.
Main Results:
- The alpha defensin lateral flow test demonstrated high sensitivity (89.5%) and specificity (94.8%) in the prospective cohort.
- In the supplemental cohort, sensitivity was 98.5% and specificity was 98.2%.
- No significant difference in diagnostic performance was observed compared to the alpha defensin enzyme-linked immunosorbent assay (ELISA).
Conclusions:
- The alpha defensin lateral flow test exhibits solid diagnostic performance for PJI.
- The test has received U.S. Food and Drug Administration (FDA) authorization.
- The lateral flow test is intended as an aid in the clinical diagnosis of PJI.
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