PRACTICUM VI EXAMINATION OF occult blood in feces Practice : Examination for occult blood in the feces There are several types of occult blood examination methods that are often used, such as the benzidine test, based on determining the peroxidase or oxyperoxidase activity of erythrocytes. There are no particular dietary restrictions required during this examination, however, large amounts of vitamin C can affect the results of the test so that it occursfalse negative. Therefore, at least 3 days before sampling, vitamin C consumption is limited to less than 250 mg/day. Some things that also need to be considered in the occult blood test are the use of drugs, such as aspirin and non-steroidal anti-inflammatory drugs (NSAIDs), which can cause minor bleeding in the mucosal walls. Indications for examination of occult blood in feces: - Benign or malignant cancerous growth - Intestinal infections that cause inflammation - Hemorrhoids that can burst and cause bleeding - Diverticular disease is caused by disorders of the colon wall - Abnormalities in the blood vessels in the large intestine Sampling : - Avoid sampling during menstruation - Avoid stool samples that have fallen to the bottom of the toilet - Before the examination, tell your doctor if you are using medication or have previously had an X-ray using barrium contrast agent A. CHEMICAL FEATURE METHOD (Benzidine Test) Purpose: to find out small bleeding that cannot be noticed on microscopic and macroscopic examination of feces Principle: Hemoglobin which acts as a peroxidase will dissolve hydrogen peroxide to water and 0 nascens (On). On will oxidize certain dyes causing color changes Tools & Materials: - Glass objects - Drop pipette - Mixer - Alkaline benzidine crystals - Hydrogen peroxide (H2O2) 3% - Acetic acid - Stool sample Ways of working: 1. Prepare the tools and materials that will be used 2. Take a stool sample and place it on an appropriate glass object 3. Add a little benzidine powder and mix thoroughly 4. Add 2 drops of acetic acid, then homogenize 5. Add 2 drops of 3% H2O2, mix homogeneously and observe the color change that occur The benzidine examination is said to be sensitive but less specific because it is heavily influenced by diet and the drugs the patient is taking. Besides that, benzidine is said to have carcinogenic effects and is starting to be abandoned. B. IMMUNOLOGICAL METHOD (Rapid Chromatographic Immunoassay) This is a rapid test to detect occult blood in feces at low levels. This rapid test uses the principledouble antibody sandwich assayto detect up to 50 ng/ml hemoglobin in feces or 6 ul hemoglobin/g feces. Working principle: This is a qualitative examination using principles immunoassayto detect blood in feces. The stool sample will react with anti-hemoglobin antibodies in the chromatography membrane to form a color line. Work procedures : 1. Opened and closedspecimen collection tube, then take stool samples in at least 3 different places using the tip of the stick 2. Close tightly, then shake the sample with extraction buffer. This examination sample can be stored for 6 months at a temperature of -200C if no examination is carried out within 1 hour 3. Open the FOB test strip 4. Through the tipspecimen collection tube, drop 2 drops of sample (± 90µl) into the sample well (S), then run the timer. Avoid the formation of air bubbles in the sample well (S) 5. Wait until the red line appears. 6. Readings are taken at the 5th minute, and do not interpret the results after 10 minutes.