The "HemoQuant" test: a specific and quantitative determination of heme (hemoglobin) in feces and other materials
Schwartz, S.; Dahl, J.; Ellefson, M.; Ahlquist, D.
Clinical Chemistry 29(12): 2061-2067
1983
ISSN/ISBN: 0009-9147 PMID: 6640900 Document Number: 203068
We describe a new, specific, quantitative method for fecal blood, based on conversion of nonfluorescing heme to fluorescing porphyrins, that obviates serious deficiencies inherent in currently used tests. A two-reagent system is used to determine the two hemoglobin-related fractions that are found in feces. The hot citric acid extract includes only the variable fraction of porphyrins that have been preformed from heme in the intestinal tract; this often is the major fraction. Total hemoglobin is indirectly determined by reaction with heated oxalic acid:FeSO4 reagent, which converts the remaining heme to porphyrin without loss of the preformed porphyrins. A three-step purification procedure eliminates interfering materials. Analytical recovery of added hemoglobin is linearly related to concentration over a several-thousand-fold range. The assay is equally applicable to whole blood or to sub-microgram amounts of hemoglobin in the 8-mg (wet weight) fecal sample tested. Quality control by liquid chromatographic and fluorometric analysis documents fluorescence specificity of the heme-derived porphyrins.