[Measurement of fecal hemoglobin-haptoglobin complex as a new diagnostic tool of lower gastrointestinal tract diseases].

An immunoradiometric assay (IRMA) of human hemoglobin-haptoglobin complex (Hb-Hp complex) was established for the purpose of clinical application as a new fecal occult blood test. This IRMA reacted with free human Hb and Hp as well as Hb-Hp complex and its measurable range was 3.125 through 800 ng/ml. Its cross-reaction with other animal Hb and serum was little enough to neglect. The immunoreactivity of Hb-Hp complex was more stable than that of free Hb in incubation with gastric juice and fecal extracts. Of 48 stools from the patients with colorectal cancer, 44 (91.7%) gave positive (above 10 ng/ml in fecal extract) test in Hb-Hp complex-IRMA, whereas 35 (72.9%) (p < 0.05) gave positive result (above 10 ng/ml in fecal extract) in Hb-IRMA. At proximal site of cancer, positive rate of Hb-Hp complex in feces was significantly high (p < 0.05) compared with Hb. Of 64 stools from the patients with colorectal adenomas, 56 (87.5%) gave positive test in Hb-Hp complex, whereas 46 (71.9%) (p < 0.05), 28 (43.8%) (p < 0.01) and 33 (51.5%) showed positive in Hp, Hb and Guaiac test, respectively. In every size and site of adenoma, fecal Hb-Hp complex showed significantly high (p < 0.01) positivity compared with Hb and Guaiac test. These results suggest that the measurement of Hb-Hp complex in fecal extracts may be a useful tool for the early detection of lower gastrointestinal diseases.