Abstract

In this study, we evaluated the performance of the flow cytometer-based Sysmex UF-5000 automated urine analyzer as a screening tool for ruling out urinary tract infections in elderly patients presenting at the emergency department. A total of 1119 unselected patient samples (including 544 samples from elderly patients) submitted for urine culture were included in this study. Samples were measured on UF-5000 and dipsticks and the results were compared with interpretation of culture results, which is the gold standard. We obtained a diagnostic sensitivity of 99% and specificity of 51% with a low rate of false negatives (0.2%) and a negative predictive value of 99% at 10⁸ colony forming bacteria/L (CFB/L). A bacterial count ≥ 50x10⁶/L or yeast like cells ≥ 25x10⁶/L was used as the cutoff value. At this cutoff value, 30% of the urine cultures would have been redundant. This resulted in 35% false positive samples, mainly due to particle contamination or nongrowing bacteria. In comparison, at best, the dipsticks have a diagnostic sensitivity of 89%, a specificity of 52% and a negative predictive value of 92% at 10⁸ CFB/L.

摘要

在这项研究中，我们评估了基于流式细胞仪的 Sysmex UF-5000 自动尿液分析仪的性能，作为排除急诊科老年患者尿路感染的筛查工具。本研究共纳入了 1119 份未选择的患者样本（包括来自老年患者的 544 份样本）进行尿培养。在 UF-5000 和试纸上测量样品，并将结果与​​培养结果的解释进行比较，这是金标准。我们获得了 99% 的诊断敏感性和 51% 的特异性，假阴性率低 (0.2%)，在 10 ⁸菌落形成细菌/L (CFB/L) 时的阴性预测值为 99%。A 细菌计数 ≥ 50x10 ⁶ /L 或酵母样细胞 ≥ 25x10 ⁶/L 用作截止值。在这个临界值下，30% 的尿培养是多余的。这导致了 35% 的假阳性样本，主要是由于颗粒污染或非生长细菌。相比之下，在 10 ⁸ CFB/L 时，试纸条的诊断灵敏度最多为 89%，特异性为 52%，阴性预测值为 92%。