Alpha-defensin lateral-flow test yields high sensitivity, specificity for periprosthetic joint infection
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The alpha-defensin lateral-flow test showed a high sensitivity and specificity in detecting periprosthetic joint infection prior to revision total joint arthroplasty, according to recent study results.
In a prospective, multicenter, adjudicator blinded clinical trial, Carl A. Deirmengian, MD, FAAOS, and colleagues conducted an alpha-defensin lateral-flow test for periprosthetic joint infection among 305 patients prior to revision hip or knee arthroplasty as well as in 65 laboratory-derived fresh synovial fluid samples of patients that met Musculoskeletal Infection Society criteria for periprosthetic joint infection.
“Twenty-one percent of our patients had sinus tract, and as you well know sinus tracts make diagnostic tests not work that well because you are emptying the joint continuously,” Deirmengian said at the Orthopaedic Research Society Annual Meeting, where he presented findings of his study and won the American Academy of Orthopaedic Surgeons Elizabeth Winston Lanier Award. “Secondly, 17 of the 305 patient samples included in this study were basically pure blood ... but we included them in the study because we did not prioritize them as exclusions in the beginning.”
Deirmengian reported the alpha-defensin lateral-flow test had a 90% sensitivity and 95% specificity. When they excluded the pure blood samples, Deirmengian said the sensitivity went up to 95%. He added prior antibiotic or underlying systemic inflammatory diagnoses had no statistically significant impact on the results.
“[The alpha-defensin lateral-flow test] is a really good test,” Deirmengian said. “Obviously, you cannot use it alone. Obviously, it is wrong sometimes, no test is perfect. But from a how good is this test standpoint, from any standard in medicine, it is a pretty good test.” – by Casey Tingle
Reference:
Deirmengian CA, et al. ePaper 066. Presented at: American Academy of Orthopaedic Surgeons Annual Meeting; March 24-28, 2020 (meeting canceled).
Disclosure: Deirmengian reports he is a paid consultant for Biomet, Biostar Ventures and Zimmer; has stock or stock options in Biostar Ventures, Domain and Trice; and is a paid presenter or speaker and receives research support from Zimmer.
Perspective
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Karan Goswami, MD
Carl A. Deirmengian, MD, and colleagues present a prospective multicenter study comparing the diagnostic performance of the alpha-defensin lateral flow test against the Musculoskeletal Infection Society criteria for periprosthetic joint infection. The study was submitted as part of their FDA approval for the test as a de novo diagnostic device.
A total of 390 subjects, comprising patients and lab-derived synovial fluid specimens, were enrolled. Each was classified by three blinded reviewers per the 2013 Musculoskeletal Infection Society criteria. Performance of the alpha-defensin lateral flow assay vs. the Musculoskeletal Infection Society gold standard was determined. Sensitivity of the lateral flow test was 94.3% and specificity was 94.8%. Furthermore, the specificity of the lateral flow test was not significantly different to the alpha-defensin laboratory test. The authors conclude that the alpha-defensin lateral-flow test for periprosthetic joint infection had excellent diagnostic performance.
While there has been debate as to the whether the qualitative point-of-care alpha-defensin lateral flow test shares the same diagnostic performance as the quantitative alpha-defensin laboratory ELISA test, these data support the notion of there being no significant difference between the two. A recent meta-analysis also echoed these findings of no difference between the lateral flow and ELISA tests in pooled cohorts (sensitivity 86% vs. 90%; P= .43 and specificity 96% vs. 97%).
Certain caveats and questions remain, however. Future studies must address the cost-effectiveness of empiric alpha-defensin testing, impact upon clinical decision-making and assess the circumstances in which testing is indicated. If reserved for only high pre-test probability cases with an indeterminate diagnosis using conventional tests, patients will incur the risk of repeat aspiration for alpha-defensin testing and potentially diminished test accuracy. Flares of crystal arthropathy or inflammatory arthritis may also confound results; however, these scenarios are pragmatically very difficult to explore with scientific rigor.
Nonetheless, the overall diagnostic potential of alpha-defensin testing has certainly been established and is further confirmed by this study.
Reference:
Kuiper JWP, et al. Clin Orthop Relat Res. 2020;doi:10.1097/CORR.0000000000001225.
Thomas Jefferson University
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