Department of Orthopaedic Surgery, The Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania.
CD Diagnostics, Zimmer Biomet, Claymont, Delaware.
J Arthroplasty. 2018 Aug;33(8):2571-2574. doi: 10.1016/j.arth.2018.03.005. Epub 2018 Mar 13.
The urinary leukocyte esterase (LE) test strip has been suggested as a good screening test for periprosthetic joint infection (PJI). The purpose of this study is to compare the diagnostic profile of LE assays from different manufacturers and determine whether the LE test strip is a good rule-out test.
Synovial fluid samples (N = 344), sent to 1 laboratory for PJI testing, were used in this prospective study. Four different tests for synovial fluid LE were simultaneously evaluated for their performance in detecting white blood cell (WBC) positive samples (>3000 cells/µL).
Both neutrophil elastase immunoassays demonstrated greater sensitivity than urinary LE test strips (92.0% and 90.8% vs 72.4% and 80.3%; all P < 0.011). Fifty-three percent of false-negative urinary LE test strip results clearly missed the presence of elevated levels of synovial fluid LE. Invalid urinary LE test strip results were 4-fold more likely among WBC (+) compared with WBC (-) samples (27.0% vs 6.8%; P < 0.0001). The combined failure to detect an elevated WBC count, because of either false-negative or invalid results, was 47.1% and 41.4% for the Roche and Siemens test strips, respectively.
This study agrees with the existing literature demonstrating that the LE test strips are among the lowest sensitivity tests for PJI. The urinary LE tests strips should not be used to rule-out PJI, as they often fail to detect abundant levels of LE in synovial fluid. Instead, it is more appropriate to use the (++) LE test strip result as a secondary confirmatory rule-in test for PJI because of its high specificity.
尿白细胞酯酶（LE）检测试带已被推荐作为一种用于诊断假体周围关节感染（PJI）的筛选试验。本研究旨在比较不同制造商的 LE 检测试带的诊断性能，并确定 LE 检测试带是否是一种良好的排除性检测试验。
本前瞻性研究共纳入了 344 份滑膜液样本，这些样本均被送至同一家实验室进行 PJI 检测。本研究同时评估了 4 种不同的滑膜液 LE 检测试带，以确定其在检测白细胞（WBC）阳性样本（>3000 个/μL）方面的性能。
两种中性粒细胞弹性蛋白酶免疫测定法的敏感性均高于尿 LE 检测试带（92.0%和 90.8% vs 72.4%和 80.3%；均 P < 0.011）。53%的假阴性尿 LE 检测试带结果明显漏诊了滑膜液 LE 水平升高。与 WBC（-）样本相比，WBC（+）样本中无效的尿 LE 检测试带结果的可能性高 4 倍（27.0% vs 6.8%；P < 0.0001）。罗氏和西门子试带分别有 47.1%和 41.4%的样本因假阴性或无效结果而未能同时检测到升高的 WBC 计数。
本研究与现有的文献一致，表明 LE 检测试带是用于诊断 PJI 的敏感性最低的检测试验之一。由于尿 LE 检测试带经常无法检测到滑膜液中丰富的 LE 水平，因此不应将其用于排除 PJI。相反，由于其高特异性，将（++）LE 检测试带结果用作 PJI 的二级确认性规则纳入试验更为合适。
