An immunologic test for fecal occult blood by counter immunoelectrophoresis. Higher sensitivity and higher positive reactions in colorectal cancer than single radial immunodiffusion and hemoccult test.

A new immunologic fecal occult blood test has been developed employing counter immunoelectrophoresis (CIEP) with anti-human hemoglobin Ao antiserum (anti-HbAo). Minimum detectable hemoglobin in hemolysate was 7, 9, and 7 micrograms/ml by CIEP, single radial immunodiffusion (SRID), and Hemoccult test (SmithKline Beckman), respectively. The values in stool were 0.5, 1.0, 3.0 mg hemoglobin/g stool in the same order. CIEP was more sensitive than SRID in detecting hemoglobin both in hemolysate and in feces. Of 38 stools from the patients with colorectal cancer, 29 (76%) gave positive tests in CIEP, whereas 22 (58%) (P less than 0.005), and 18 (47%) (P less than 0.05) gave positive tests in SRID and Hemoccult test, respectively. In every stage and at every site of cancer, CIEP showed the highest positive tests. CIEP did not give any false-positive reaction in specimens from 20 patients without gastrointestinal lesion or from 34 asymptomatic healthy controls without diet restriction, whereas Hemoccult test gave one and three positive reactions in these groups. These results clearly indicate that CIEP is specific and more sensitive to human hemoglobin than any other previous methods. CIEP is expected to have a potential for mass screening of colorectal cancer.