BACKGROUND Urinary neutrophil gelatinase-associated lipocalin is an established biomarker of acute kidney injury, however, the levels are affected by the number of white blood cells in the urine. As we suspected the portion of the urinary stream sampled could also have a significant influence on the urinary NGAL levels in female subjects, we investigated the influence of the urine sampling procedure on the urinary NGAL levels. METHODS We collected 25-mL urinary specimens from each of initial-stream and midstream urinary specimens, including 28 healthy adult female volunteers without kidney diseases or UTI. Then we compared the WBC count, NGAL level, and creatinine level between these specimens. RESULTS We observed that the urinary NGAL levels were significantly higher in the specimens obtained from initial-stream urinary samples than in midstream specimens, and that they were strongly correlated with the leukocyte esterase activity and WBC count. Moreover, the differences in the urinary NGAL levels between the initial- and midstream urine samples were greater for initial-stream samples with higher leukocyte esterase activities, with a significant difference even for the initial-stream samples with no detectable leukocyte esterase activity. CONCLUSION Therefore, midstream urine sampling is strongly recommended for accurate measurement of the urinary NGAL levels.

中文翻译：

---

在健康女性受试者中，中流尿液采样对于准确测量中性粒细胞明胶酶相关脂钙蛋白的尿水平是必要的。

背景技术尿中性粒细胞明胶酶相关的脂环蛋白是急性肾损伤的确定的生物标志物，但是，其水平受尿中白细胞数量的影响。由于我们怀疑采样的一部分尿流也可能对女性受试者的尿NGAL水平产生显着影响，因此我们研究了尿液采样程序对尿NGAL水平的影响。方法我们从初始和中期尿液样本中分别收集了25 mL尿液样本，包括28名没有肾脏疾病或UTI的健康成年女性志愿者。然后，我们比较了这些标本之间的白细胞计数，NGAL水平和肌酐水平。结果我们观察到，从初始尿液样本中获取的尿样中的尿NGAL水平明显高于中游样本，并且它们与白细胞酯酶活性和WBC计数密切相关。此外，对于具有较高白细胞酯酶活性的原始流样品，初始和中流尿液样本中尿NGAL水平的差异更大，即使对于没有可检测到的白细胞酯酶活性的原始流样品，其尿NGAL水平也存在显着差异。结论因此，强烈建议对中游尿液采样以准确测量尿中的NGAL水平。对于具有较高白细胞酯酶活性的原始流样品，初始和中游尿样之间的尿NGAL水平差异更大，即使对于没有可检测到的白细胞酯酶活性的原始流样品，其尿NGAL水平也存在显着差异。结论因此，强烈建议对中游尿液采样以准确测量尿中的NGAL水平。对于具有较高白细胞酯酶活性的原始流样品，初始和中游尿样之间的尿NGAL水平差异更大，即使对于没有可检测到的白细胞酯酶活性的原始流样品，其尿NGAL水平也存在显着差异。结论因此，强烈建议对中游尿液采样以准确测量尿中的NGAL水平。