New screening method for occult gastrointestinal bleeding: immunologic and guaiac slide tests

Area of Science:

• Gastroenterology
• Clinical Diagnostics
• Biochemistry

Background:

• Effective screening for gastrointestinal pathology, including colorectal cancer, requires a specific, sensitive, and differentiating test for human hemoglobin in stool.
• Current guaiac-based tests like Hemoccult II lack specificity for human blood and cannot distinguish bleeding sources (upper vs. lower GI tract).

Purpose of the Study:

• To compare the diagnostic accuracy of a radial immunodiffusion slide test for human hemoglobin against the Hemoccult II guaiac test.
• To evaluate the potential of an immunologic test to overcome the limitations of guaiac-based fecal occult blood tests.

Main Methods:

• A four-year comparative study involving 211 patients with diagnosed gastrointestinal problems.
• Radial immunodiffusion slide test and Hemoccult II guaiac test were performed on patient stool samples.
• Results were correlated with diagnoses obtained via endoscopy, radiography, and other procedures.

Main Results:

• Hemoccult II had a 21% detection rate for upper GI bleeding (9/41 cases).
• The radial immunodiffusion test demonstrated 92% accuracy for upper GI bleeding (3 positive, 38 negative).
• Both tests showed similar effectiveness for lower GI bleeding (37% accuracy).

Conclusions:

• The immunologic test offers superior accuracy for detecting upper gastrointestinal bleeding compared to Hemoccult II.
• The immunologic test may address the deficiencies of guaiac-based tests in gastrointestinal bleeding screening.
• Combined use of sensitive immunologic and guaiac tests could meet screening requirements.