Purpose

Periprosthetic joint infections (PJIs) remain a challenging complication after shoulder arthroplasty. The antimicrobial peptide α-defensin has been proposed as a new synovial fluid biomarker in diagnosing PJIs. To date, only little data are available on the diagnostic accuracy of α-defensin in shoulder PJIs; thus, we aimed to evaluate its diagnostic value in a cohort of patients with a suspected shoulder PJI.

Methods

Between June 2016 and June 2018, we prospectively enrolled patients with a diagnostic shoulder aspiration due to painful shoulder arthroplasty or planned revision surgery. PJI diagnostics were performed according to the Musculoskeletal Infection Society (MSIS) criteria. All patients with an antibiotic therapy within two weeks before enrollment, insufficient amount of synovial aspirate, or bloody aspiration were excluded. α-Defensin was measured in the synovial fluid using the α-defensin lateral flow (ADLF) test (Synovasure®).

Results

Out of 60 patients, we could include 29 (59% female) patients with a mean age of 70 (range, 50–92) years. A shoulder PJI was detected in five cases (Staphylococcus aureus, n = 2; Staphylococcus epidermidis, n = 2; Cutibacterium acnes, n = 1). The ADLF test was positive in seven out of 29 cases. According to the MSIS criteria, the ADLF test was false-negative in two patients and false-positive in four patients, resulting in sensitivity, specificity, and positive and negative predictive value of 60%, 83%, 43%, and 91%, respectively. The overall accuracy was 79%.

Conclusion

The ALDF test does not appear to be useful in predicting shoulder PJIs but may be used as an additional diagnostic factor in rejecting these infections.

中文翻译：

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α-防御素侧向流动试验似乎不能用于预测肩关节假体周围感染。

目的

肩关节置换术后，假体周围感染（PJI）仍然是具有挑战性的并发症。抗菌肽α-防御素已被提出作为诊断PJI的一种新的滑液生物标志物。迄今为止，关于肩部PJI中α-防御素的诊断准确性的数据很少。因此，我们旨在评估其在怀疑肩部PJI患者中的诊断价值。

方法

在2016年6月至2018年6月之间，我们前瞻性招募了因肩关节置换术疼痛或计划进行翻修手术而诊断为肩部误吸的患者。根据肌肉骨骼感染学会（MSIS）的标准进行PJI诊断。所有入选前两周内接受抗生素治疗，滑膜抽吸量不足或有血性抽吸的患者均被排除。使用α-防御素横向流动（ADLF）测试（Synovasure®）在滑液中测量α-防御素。

结果

在60名患者中，我们可能包括29名（59％为女性）平均年龄为70岁（50-92岁）的患者。在5例病例中检测到肩部PJI（金黄色葡萄球菌，n  = 2；表皮葡萄球菌，n  = 2；痤疮皮肤杆菌，n  = 1）。在29例病例中，有7例的ADLF检测呈阳性。根据MSIS标准，ADLF测试两名患者为假阴性，四名患者为假阳性，因此敏感性，特异性以及阳性和阴性预测值分别为60％，83％，43％和91％，分别。总体准确性为79％。

结论

ALDF测试对于预测肩部PJI似乎没有帮助，但可以用作排除这些感染的其他诊断因素。