Microbiology Service, Hospital Universitario de San Juan, Alicante, Spain.
Infectious Diseases Unit, Hospital General Universitario de Elche, Alicante, Spain.
Ann Lab Med. 2019 Sep;39(5):464-469. doi: 10.3343/alm.2019.39.5.464.
Negative urine cultures to rule out urinary tract infections (UTI) generate a considerable laboratory workload; thus, a rapid screening test is desirable. We evaluated the performance of a new automated microscopy analyzer, cobas u 701 (Roche Diagnostics International, Rotkreuz, Switzerland) for the screening of UTI, and developed a rule-out strategy to reduce the number of samples requiring culture. We also assessed squamous epithelial cell (SEC) count as a predictor of culture contamination.
In total, 1,604 urine samples from outpatients were analyzed with cobas u 701 and culture. Bacterial (BAC) and white blood cell (WBC) counts were used for sample interpretation. To determine a useful cut-off point to predict negative cultures, we selected the highest sensitivity and specificity values obtained from ROC curves. Diagnostic accuracy by age and gender was evaluated.
Urine culture showed growth of ≥10⁴ colony forming units (CFU)/mL in 256 samples (16.0%). The highest sensitivity (91.8%) and specificity (68.4%) were obtained for cut-off points of 119 BAC/μL and 22 WBC/μL. The combination of BAC and WBC improved the performance of the rule-out strategy with a low rate of false-negative results (1.5%) and a high negative predictive value (NPV, 97.3%). Fifty-seven percent of the samples would not have required culture. SEC count was a poor predictor of culture contamination.
cobas u 701 can substantially reduce the number of urine samples requiring culture, with a low false-negative rate and a high NPV.
为了排除尿路感染（UTI）而进行的阴性尿液培养会产生相当大的实验室工作量；因此，需要一种快速的筛选试验。我们评估了 cobas u 701（罗氏诊断国际公司，瑞士罗特克吕茨）用于 UTI 筛查的性能，并制定了排除策略以减少需要培养的样本数量。我们还评估了鳞状上皮细胞（SEC）计数作为培养污染的预测指标。
共分析了 1604 例来自门诊患者的尿液样本，使用 cobas u 701 和培养。细菌（BAC）和白细胞（WBC）计数用于样本解释。为了确定一个有用的截断值来预测阴性培养，我们从 ROC 曲线中选择了最高的敏感性和特异性值。按年龄和性别评估诊断准确性。
尿液培养显示 256 个样本（16.0%）≥10⁴菌落形成单位（CFU）/mL。119 BAC/μL 和 22 WBC/μL 的截断值分别获得了最高的敏感性（91.8%）和特异性（68.4%）。BAC 和 WBC 的组合提高了排除策略的性能，假阴性率低（1.5%），阴性预测值高（97.3%）。57%的样本不需要培养。SEC 计数是培养污染的一个较差的预测指标。
cobas u 701 可以大大减少需要培养的尿液样本数量，具有低假阴性率和高阴性预测值。
