Jaffe R M, Lawrence L, Schmid A, MacLowry J D
Am J Clin Pathol. 1979 Sep;72(3):468-70. doi: 10.1093/ajcp/72.3.468.
Review of results of 9,620 consecutive urinalyses revealed 892 urines that contained microscopic evidence of erythrocytes and 98 for which there were discrepancies between microscopic evidence of hematuria (greater than 20 erythrocytes/high-power field) and chemical detection of blood (0 or "1+" when results should be "3+"). Eleven specimens (from ten patients) showed negative results of chemical tests for blood and greater than 40 erythrocytes/high-power field (HPF). Nine of these patients were receiving ascorbic acid supplementation. In a random sample of 20 patients with greater than 40 erythrocytes/HPF and strongly positive tests for blood, none was receiving ascorbic acid, a significant difference by chi-square analysis. In a prospective study, low levels of ascorbic acid inhibited chemical detection of blood. At 25 mg/dl ascorbic acid, 10--20 erythrocytes/HPF could not be detected; at 35 mg/dl ascorbic acid, greater than 20 erythrocytes/HPF were undetectable. For quantitation of the low level at which ascorbic acid inhibits chemical detection of blood, fresh urine specimens should be analyzed. Ascorbic acid is oxidated in vitro to products that partially inhibit detection of blood yet do not assay as ascorbic acid.
对连续9620份尿液分析结果的回顾显示，892份尿液含有红细胞的显微镜证据，98份尿液在血尿的显微镜证据（每高倍视野超过20个红细胞）与血液化学检测结果（结果应为“3+”时为0或“1+”）之间存在差异。11份标本（来自10名患者）血液化学检测结果为阴性，但每高倍视野红细胞超过40个。其中9名患者正在补充维生素C。在20名每高倍视野红细胞超过40个且血液检测呈强阳性的患者随机样本中，无人补充维生素C，经卡方分析差异显著。在一项前瞻性研究中，低水平的维生素C会抑制血液的化学检测。当维生素C水平为25mg/dl时，每高倍视野10 - 20个红细胞无法检测到；当维生素C水平为35mg/dl时，每高倍视野超过20个红细胞无法检测到。为了定量维生素C抑制血液化学检测的低水平，应分析新鲜尿液标本。维生素C在体外被氧化为部分抑制血液检测但无法检测为维生素C的产物。
