This month I will be introducing to you guys about a new method that I learnt in the microbiology department how to detect the presence of occult blood in stools specimens.
My company uses a kit called Hema-Screen. It is a guaiac slide test for the qualitative detection of fecal occult blood. It is a useful aid in diagnosis of a number of gastrointestinal disorders.
The detection of occult blood is critical to many gastrointestinal diseases. The presence of occult blood in fecal material may indicate gastrointestinal pathology such as hemorrhoids, diverticulitis, fissures, colitis or colorectal cancer. Hence Hema-Screen is a simple, aesthetic, inexpensive test designed for the use in collection and preparation of stool specimens. It overcomes the instability of guaiac solution and the hypersensitivity of benezidine and ortho-tolidine.
The principle of the test is as follows. Hema-screen is composed of guaiac impregnated paper enclosed in a cardboard frame, which permits sample application to one side, and development and interpretation on the reverse side. The process involves placing 2 specimens onto the guaiac paper.
Hema screen, like all guaiac paper test for occult blood, is based on the oxidation of phenolic compounds present in the guaiac to quinines resulting in production of the blue color. Because of its similarity to the prosthetic group of peroxidase, the hematin portion of the hemoglobin molecule can function in a pseudoenzymatic manner, catalyzing the oxidation of guaiac. So when a fecal specimen containing occult blood is applied on the test paper, contact is made between hemoglobin and the guaiac. A pseudoperoxidase reaction will occur upon addition of the developer solution, with a blue chromagen formed proportionally to thee concentration of hemoglobins. The color reaction will occur after 30 seconds.
If a positive result is obtained with the test, a follow-up with additional diagnostic tests, as soon as possible, is essential. As with any occult blood test, results with Hema-Screen cannot be consider conclusive evidence of the presence or absence of gastrointestinal bleeding or pathology. The test is not intended as a replacement for other diagnostic procedures such as proctosigmoidoscopy examination, barium enema, and X-ray studies.