Ahlquist D A, McGill D B, Schwartz S, Taylor W F, Ellefson M, Owen R A
Ann Intern Med. 1984 Sep;101(3):297-302. doi: 10.7326/0003-4819-101-3-297.
HemoQuant, an assay based on heme-derived porphyrin, quantifies both total fecal hemoglobin ant that fraction already converted to porphyrin by gut flora (the intestinal converted fraction). Recovery by HemoQuant of blood added to stools exceeded 99% and was not affected by ascorbic acid, iron, or other additives. HemoQuant was used to evaluate the performance of Hemoccult on 1018 stools. Hemoccult sensitivity differed widely, remaining negative with up to 42.5 mg hemoglobin per gram of stool (about 43 mL/d of blood) but positive with only 0.04 mg of hemoglobin per gram of stool. Driest stools tended to be Hemoccult-negative and the wettest Hemoccult-positive. Hemoccult-negative stools became positive after aqueous dilution independent of hemoglobin concentration. The intestinal converted fraction, not detected by guaiac tests, often constituted most of the fecal hemoglobin equivalents and was significantly higher in Hemoccult-negative than in Hemoccult-positive stools. Hemoccult lost reactivity during fecal storage due to progressive heme degradation. Frequent false-negative and false-positive reactions of Hemoccult were explained largely by variations in stool liquidity and heme degradation.
血隐定量检测法是一种基于血红素衍生卟啉的检测方法，可对粪便中的总血红蛋白以及已被肠道菌群转化为卟啉的部分（肠道转化部分）进行定量。向粪便中添加血液后，血隐定量检测法的回收率超过99%，且不受抗坏血酸、铁或其他添加剂的影响。血隐定量检测法被用于评估1018份粪便样本上的愈创木脂隐血试验的性能。愈创木脂隐血试验的灵敏度差异很大，每克粪便中血红蛋白含量高达42.5毫克（约相当于每日失血43毫升）时仍呈阴性，但每克粪便中血红蛋白含量仅为0.04毫克时就呈阳性。最干燥的粪便往往愈创木脂隐血试验呈阴性，而最湿润的则呈阳性。无论血红蛋白浓度如何，经水稀释后，愈创木脂隐血试验呈阴性的粪便会转为阳性。愈创木脂试验无法检测到的肠道转化部分，通常构成了粪便中大部分血红蛋白当量，且在愈创木脂隐血试验呈阴性的粪便中显著高于呈阳性的粪便。由于血红素逐渐降解，愈创木脂隐血试验在粪便储存期间会失去反应活性。愈创木脂隐血试验频繁出现假阴性和假阳性反应，很大程度上是由粪便流动性和血红素降解的差异所导致的。
