About Stool Tests Stool (or feces) is usually thought of as nothing but waste — something to quickly flush away. But bowel movements can provide doctors with valuable information as to what's wrong when a child has a problem in the stomach, intestines, or another part of the gastrointestinal system. A doctor may order a stool collection to test for a variety of possible conditions, including: allergy or inflammation in the body, such as part of the evaluation of milk protein allergy in infants infection, as caused by some types of bacteria, viruses, or parasites that invade the gastrointestinal system digestive problems, such as the malabsorption of certain sugars, fats, or nutrients bleeding inside of the gastrointestinal tract The most common reason to test stool is to determine whether a type of bacteria or parasite may be infecting the intestines. Many microscopic organisms living in the intestines are necessary for normal digestion. If the intestines become infected with harmful bacteria or parasites, though, it can cause problems like certain types of bloody diarrhea, and testing stool can help find the cause. Stool samples are also sometimes analyzed for what they contain; for instance, examining the fat content. Normally, fat is completely absorbed from the intestine, and the stool contains virtually no fat. In certain types of digestive disorders, however, fat is incompletely absorbed and remains in the stool 1.Fecal pH test A fecal pH test is one where a specimen of feces is tested for acidity in order to diagnose a medical condition. Human feces is normally alkaline. An acidic stool can indicate a digestive problem such as lactose intolerance or a contagion such as E. coli or Rotavirus. Test procedure The test is fast and can be performed in a doctor's office. A patient must not be receiving antibiotics. At least half a milliliter of feces is collected and a strip of nitrazine paper is dipped in the sample and compared against a color scale. A pH of less than 5.5 indicates an acidic sample. 2. Fecal fat test In medicine, the fecal fat test is a diagnostic test for fat malabsorption conditions, which lead to excess fat in the feces (steatorrhea). (Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal (GI) tract.Impairment can be of single or multiple nutrients depending on the abnormality. This may lead to malnutrition and a variety of anaemias.) In the small intestine, dietary fat (primarily triglycerides) is digested by enzymes such as pancreatic lipase into smaller molecules which can be absorbed through the wall of the small intestine and enter the circulation for metabolism and storage. As fat is a valuable nutrient, human feces normally contain very little undigested fat. However, a number of diseases of the pancreas and gastrointestinal tract are characterized by fat malabsorption. Examples of such diseases are: disorders of exocrine pancreatic function, such as chronic pancreatitis, cystic fibrosis and Shwachman-Diamond syndrome (these are characterized by deficiency of pancreatic digestive enzymes) celiac disease (in which the fat malabsorption in severe cases is due to inflammatory damage to the integrity of the intestinal lining) short bowel syndrome (in which much of the small intestine has had to be surgically removed and the remaining portion cannot completely absorb all of the fat). small bowel bacterial overgrowth syndrome Microscopy In the simplest form of the fecal fat test, a random fecal specimen is submitted to the hospital laboratory and examined under a microscope after staining with a Sudan III or Sudan IV dye ("Sudan staining"). Visible amounts of fat indicate some degree of fat malabsorption. Quantitative fecal fat test Quantitative fecal fat tests measure and report an amount of fat. This usually done over a period of three days, the patient collecting all of their feces into a container. The container is thoroughly mixed to homogenize the feces, this can be done with a paint mixer. A small sample from the feces is collected. The fat content is extracted with solventsand measured by saponification (turning the fat into soap). Normally up to 7 grams of fat can be malabsorbed in people consuming 100 grams of fat per day. In patients with diarrhea, up to 12 grams of fat may be malabsorbed since the presence of diarrhea interferes with fat absorption, even when the diarrhea is not due to fat malabsorption. 3. Stool guaiac test The stool guaiac test or guaiac fecal occult blood test (gFOBT) is one of several methods that detect the presence of fecal occult blood(FOB). Fecal occult blood is blood present in the feces that is not visibly apparent. The term guaiac denotes the name of the paper surface used in the test which has a phenolic compound, alpha-guaiaconic acid, that is extracted from the wood resin of Guaiacum trees Methodology The stool guaiac test involves fasting from iron supplements, red meat (the blood it contains can turn the test positive), certain vegetables (which contain a chemical with peroxidase properties that can turn the test positive), and vitamin C and citrus fruits (which can turn the test falsely negative) for a period of time before the test. It has been suggested that cucumber, cauliflower and horseradish, and often other vegetables, should be avoided for three days before the test. In testing, feces are applied to a thick piece of paper attached to a thin film coated with guaiac. Either the patient or medical professional smears a small fecal sample on to the film. The fecal sample can be obtained by digital rectal examination or by wiping soiled toilet tissue on the film. Only a small sample for smearing is necessary; a large sample of stool may impede an accurate test. Both sides of the test card can be peeled open, to access the inner guaiac paper. One side of the card is marked for application of the stool and the other is for the developer fluid. After applying the feces, one or two drops of hydrogen peroxide are then dripped on to the other side of the film, and it is observed for a rapid blue color change. When the hydrogen peroxide is dripped on to the guaiac paper, it oxidizes the alpha- guaiaconic acid to a blue colored quinone. Normally, when no blood and no peroxidases or catalases from vegetables are present, this oxidation occurs very slowly. Heme, a component of hemoglobin found in blood, catalyzes this reaction, giving a result in about two seconds. Therefore, a positive test result is one where there is a quick and intense blue color change of the film. Analytical interpretation The guaiac test can often be false-positive which is a positive test result when there is in fact no source of bleeding. This is particularly common if the recommended dietary preparation is not followed, as the heme in red meat or the peroxidase or catalase activity in vegetables, especially if uncooked, can cause analytical false positives. Vitamin C can cause analytical false negatives due to its anti-oxidant properties inhibiting the color reaction. If the card has not been promptly developed, the water content of the feces decreases, and this can reduce the detection of blood. Although rehydration of stored samples can reverse this effect this is not recommended because the test becomes unduly analytically sensitive and thus much less specific. Some stool specimens have a high bile content that causes a green color to show after applying the developer drops. If entirely green, such samples are negative, but if questionnably green to blue, such samples are designated positive. The package insert guidelines from the manufacturers, for example Hemoccult SENSA, recommend that nonsteroidal anti-inflammatory drugs (NSAID), such as ibuprofen and aspirin, and iron supplements be discontinued for at least several days before the tests. There is a concern that these agents may irritate the body and cause biologically positive tests even in the absence of a more substantial illness, but there is some doubt about how frequently this occurs with NSAID medication. Although both iron and bismuth containing products such as antacids and antidiarrheals can cause dark stools that are occasionally confused as containing blood, actual bleeding from iron is unusual. There is no consensus on whether to stop warfarin before a guaiac test. Even when using anticoagulants a high proportion of positive guaiac tests were found to be due to diagnosable lesions, suggesting anticoagulants may not cause bleeding unless there is an abnormality.
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