Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Several noninvasive tests are available to detect gastrointestinal (GI) bleeding. However, guaiac type and immunochemical tests for occult bleeding are affected by the presence of reducing or oxidizing substances and are insensitive for the detection of proximal gut bleeding, where most clinically significant occult GI bleeding occurs.
The HemoQuant test is the most reliable, noninvasive test currently available for detecting bleeding of the esophago-GI tract. Unlike other tests for blood in feces, this test detects both intact heme and porphyrins from partly degraded heme. Additionally, test results are not complicated by either the water content of the specimen or the presence of reducing or oxidizing substances. Furthermore, HemoQuant testing is sensitive to both proximal and distal sources of occult GI bleeding.
Detection of blood in feces
HemoQuant is the most appropriate fecal occult blood test to use in the evaluation of iron deficiency
Other useful applications include the detection of bleeding as a complication of anticoagulant therapy and other medication regimens
Elevated levels are an indicator of the presence of blood in the feces, either from benign or malignant causes.
This test is not specific for bowel cancer.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Heme from ingested red meat will increase HemoQuant test values. Patients should be advised to avoid eating red meat for 3 days before collecting specimens. Fish and poultry may be substituted.
The elevated porphyrins of intoxication porphyria, erythrocytic protoporphyria, and variegate porphyria may raise HemoQuant values in the absence of gut bleeding.
Recent studies have indicated that cancerous lesions in their early stages often do not bleed or bleed only intermittently.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
< or =2.0 mg total hemoglobin/g feces
2.0-3.0 mg total hemoglobin/g feces
2.0-4.0 mg total hemoglobin/g feces*
>3.0 mg total hemoglobin/g feces
>4.0 mg total hemoglobin/g feces*
*Alternative reference values for persons who have ingested red meat or aspirin during any of the 3 days preceding specimen collection.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Ahlquist DA, McGill DB, Schwartz S, et al: HemoQuant, a new quantitative assay for fecal hemoglobin: comparison with Hemoccult. Ann Intern Med 1984;101:297-302
2. Ahlquist DA, Wieand HS, Moertel CG, et al: Accuracy of fecal occult blood screening for colorectal neoplasia: a prospective study using Hemoccult and HemoQuant tests. JAMA 1993;269:1262-1267
3. Harewood GC, McConnell JP, Harrington JJ, et al: Detection of occult upper gastrointestinal bleeding: performance differences in fecal blood tests. Mayo Clin Proc 2002;77(1):23-28