Hi everybody. This week's my turn again to share what I've learnt with you'll.
Occult Blood Test(Blood in the stools)
Fecal occult blood test is performed as part of routine physical examination during examination of the rectum and it is a screening tool for colorectal cancer. Blood in the stools could indicate gastrointestinal diseases such as inflammatory bowel disease, gastric ulcers, etc.
-Test card(contains guaiac)
-Developing solution(contains hydrogen peroxide and denatured ethyl alsohol)
-Wooden applicator sticks
The test is based on the oxidation of guaiac by hydrogen peroxide to a blue compound. The heme portion of hemoglobin that is present in the stool will catalyse the oxidation of alpha-guaiaconic acid to form a blue colouration.
A small fecal sample is collected and a thin smear is applied on the test card using wooden applicatior sticks. The cover flap is closed and we have to wait for 2-3 mins for the stool to be absorbed into the test paper. The back of the test card is opened and a drop of the developer is added to the the guaiac paper directly over the smear and both positive and negative controls. Results are read after 1 minute and a blue colouration is indicative of occult blood. A brown colouration indicates negative results.
Patients should avoid red meat and NSAIDs as these substances can cause false positive results. Occult blood test must be done with screening endoscopy to detect colorectal cancer as a negative result for OB does not guarantee that a patient does not have colorectal cancer.
Cheong Shu Hui