High Negative Predictive Value but Moderate Overall Performance of Synovasure Compared With Joint Aspirate Culture in the Diagnosis of Prosthetic Joint Infection

TL;DR

The Synovasure test is good at ruling out joint infections but not reliable alone for confirming them, so it should be used with other diagnostic methods.

Contribution

This study evaluates Synovasure's diagnostic performance in prosthetic joint infection detection and highlights its role as an adjunct rather than a standalone test.

Findings

Synovasure has a high negative predictive value (90.48%) for excluding infection.

The test shows moderate sensitivity (78.95%) and specificity (72.38%).

Positive predictive value is low (50.85%), limiting its use as a confirmatory test alone.

Abstract

Accurate diagnosis of periprosthetic joint infection (PJI) is crucial for optimising treatment outcomes and reducing patient morbidity, mortality, and healthcare costs. This retrospective single-centre study assessed the diagnostic performance of the Synovasure alpha-defensin lateral flow (ADLF) test compared with conventional microbiological culture, which served as the reference standard. Between April 2016 and January 2019, 143 joints with suspected PJI underwent aspiration and Synovasure testing, with intraoperative tissue culture data included where available. The Synovasure ADLF test demonstrated a sensitivity of 78.95% and a specificity of 72.38%, indicating moderate diagnostic accuracy. Importantly, it achieved a high negative predictive value (90.48%), supporting its reliability in excluding infection, whereas the positive predictive value was lower (50.85%), limiting its utility as a confirmatory test when used in isolation. These findings suggest that while Synovasure provides rapid results and can be a valuable adjunct for ruling out infection, it should not replace established diagnostic methods. The test’s moderate sensitivity and specificity underline the need for cautious interpretation in clinical practice. Integrating Synovasure results with other diagnostic modalities, such as microbiological cultures, histopathology, and clinical assessment, remains essential for achieving accurate diagnosis and guiding appropriate management of PJI.

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