Fecal occult blood test Fecal occult blood test A fecal occult blood test (FOBT) is a A fecal occult blood test (FOBT) is a noninvasive test (nothing enters the body). noninvasive test (nothing enters the body). This test detects hidden (occult) blood in This test detects hidden (occult) blood in the stool. Such blood may come from the stool. Such blood may come from anywhere along the digestive tract. Hidden anywhere along the digestive tract. Hidden blood in stool is often the first, and in blood in stool is often the first, and in many cases the only, warning sign that a many cases the only, warning sign that a person has colorectal disease, including person has colorectal disease, including colon cancer colon cancer . . Fecal occult blood Fecal occult blood is a term for is a term for blood blood present in the present in the feces feces that is not visibly that is not visibly apparent. apparent.
Transcript
Fecal occult blood testFecal occult blood test A fecal occult blood test (FOBT) is a A fecal occult blood test (FOBT) is a noninvasive test (nothing enters the body). noninvasive test (nothing enters the body). This test detects hidden (occult) blood in the This test detects hidden (occult) blood in the stool. Such blood may come from anywhere stool. Such blood may come from anywhere along the digestive tract. Hidden blood in along the digestive tract. Hidden blood in stool is often the first, and in many cases the stool is often the first, and in many cases the only, warning sign that a person has only, warning sign that a person has colorectal disease, including colorectal disease, including colon cancercolon cancer. .
Fecal occult bloodFecal occult blood is a term for is a term for bloodblood present in the present in the fecesfeces that is not visibly that is not visibly apparent. apparent.
How the Test is How the Test is PerformedPerformed There are two types of FOBTs: 1) the traditional There are two types of FOBTs: 1) the traditional guaiac smear testguaiac smear test (Hemoccult, Seracult, Coloscreen), and (Hemoccult, Seracult, Coloscreen), and 2) the newer, 2) the newer, flushable reagent padsflushable reagent pads (EZ DetectT, (EZ DetectT, ColoCARE). They are both useful in detecting hidden ColoCARE). They are both useful in detecting hidden blood in the stool, and are mainly used for colorectal blood in the stool, and are mainly used for colorectal cancer screening.cancer screening.
The tests differ in the way they are performed. The The tests differ in the way they are performed. The flushable reagent pads are available without a flushable reagent pads are available without a prescription at many drugstores. In contrast, the prescription at many drugstores. In contrast, the traditional guaiac smear test is completed and traditional guaiac smear test is completed and interpreted by a medical professional, and these tests are interpreted by a medical professional, and these tests are usually available from a laboratory or a doctor's office.usually available from a laboratory or a doctor's office.
Many consumers prefer the flushable Many consumers prefer the flushable reagent pads because there is no reagent pads because there is no stool handling and no laboratory stool handling and no laboratory processing. However, health care processing. However, health care providers usually favor the guaiac providers usually favor the guaiac tests because the large studies that tests because the large studies that have shown the benefits of have shown the benefits of colon cancer screeningcolon cancer screening were done were done with guaiac tests.with guaiac tests.
Why the Test is Why the Test is PerformedPerformed
This test is mainly performed for This test is mainly performed for colorectal cancer screening. It may also colorectal cancer screening. It may also be performed in the evaluation of be performed in the evaluation of anemiaanemia..
Disadvantages:Disadvantages:Detects blood in stool, but not its cause. Detects blood in stool, but not its cause. False-positive results are common with False-positive results are common with some testing methods. This may cause some testing methods. This may cause unneeded anxiety about cancer and lead unneeded anxiety about cancer and lead to unnecessary further tests. to unnecessary further tests. False-negative results are also common False-negative results are also common and may miss disease in its early stages. and may miss disease in its early stages.
What Abnormal Results What Abnormal Results MeanMean Positive test results may indicate the following:Positive test results may indicate the following:Bleeding esophageal varicesBleeding esophageal varices Colon polypColon polyp or colon cancer or colon cancer EsophagitisEsophagitis GastritisGastritis GI (gastrointestinal) trauma GI (gastrointestinal) trauma GI GI tumortumor HemorrhoidsHemorrhoids
Fissures (cracks around the anus) Fissures (cracks around the anus) Inflammatory bowel disease Inflammatory bowel disease Peptic ulcerPeptic ulcer Complications of recent GI surgery Complications of recent GI surgery Angiodysplasia of the colonAngiodysplasia of the colon Additional conditions under which the test Additional conditions under which the test
may be performed include the following:may be performed include the following:Colon cancer screening Colon cancer screening Evaluation of anemia Evaluation of anemia
RisksRisks A negative test does not necessarily A negative test does not necessarily mean there are no colorectal diseases mean there are no colorectal diseases present. Not all polyps bleed, and not all present. Not all polyps bleed, and not all polyps bleed all the time. That is why a polyps bleed all the time. That is why a FOBT must be used with one of the FOBT must be used with one of the other more invasive screening other more invasive screening measures (sigmoidoscopy, colonoscopy, measures (sigmoidoscopy, colonoscopy, double barium contrast enema).double barium contrast enema).
ConsiderationsConsiderations ColonoscopyColonoscopy is generally recommended as is generally recommended as the preferred follow-up test to a positive the preferred follow-up test to a positive FOBT.FOBT.
Factors that can cause this test to be less Factors that can cause this test to be less accurate include the following:accurate include the following:
Bleeding gumsBleeding gums following a dental procedure following a dental procedure Eating red meat within 3 days of the test Eating red meat within 3 days of the test Eating turnips or horseradish Eating turnips or horseradish
Drugs that can cause GI bleeding include Drugs that can cause GI bleeding include anticoagulants, aspirin, colchicine, iron anticoagulants, aspirin, colchicine, iron supplements in large doses, NSAIDs (anti-supplements in large doses, NSAIDs (anti-inflammatory analgesics), and corticosteroids.inflammatory analgesics), and corticosteroids.Drugs that can cause false positive measurements Drugs that can cause false positive measurements include colchicine, iron, oxidizing drugs (for include colchicine, iron, oxidizing drugs (for example, iodine, bromides, and boric acid), and example, iodine, bromides, and boric acid), and reserpine.reserpine.Large amounts of Large amounts of vitamin Cvitamin C can cause false- can cause false-negative results on most FOBTs.negative results on most FOBTs.In general, avoiding food is not recommended, In general, avoiding food is not recommended, with the exception of red meat as described with the exception of red meat as described above.above.
How the Test is How the Test is PerformedPerformed
If the test is performed in an office or hospital, stool If the test is performed in an office or hospital, stool may be collected by a doctor during an examination.may be collected by a doctor during an examination.
If the test is performed at home, a stool sample from If the test is performed at home, a stool sample from three consecutive bowel movements is collected, three consecutive bowel movements is collected, smeared on a card, and mailed to a laboratory for smeared on a card, and mailed to a laboratory for processing. In order to ensure the accuracy of the processing. In order to ensure the accuracy of the guaiac test, follow the manufacturer's instructions on guaiac test, follow the manufacturer's instructions on how to collect the stool.how to collect the stool.
There are many ways to collect the samples. There are many ways to collect the samples. You can catch the stool on plastic wrap that is You can catch the stool on plastic wrap that is loosely placed over the toilet bowl and held in loosely placed over the toilet bowl and held in place by the toilet seat. Then put the sample place by the toilet seat. Then put the sample in a clean container. One test kit supplies a in a clean container. One test kit supplies a special toilet tissue that you use to collect the special toilet tissue that you use to collect the sample, then put the sample in a clean sample, then put the sample in a clean container. Do not take stool samples from the container. Do not take stool samples from the toilet bowl water, because this can cause toilet bowl water, because this can cause errors.errors.
For infants and young children wearing For infants and young children wearing diapers, you can line the diaper with plastic diapers, you can line the diaper with plastic wrap. The plastic wrap is positioned so that it wrap. The plastic wrap is positioned so that it keeps the stool from any urine. Mixing of urine keeps the stool from any urine. Mixing of urine and stool can spoil a good sample.and stool can spoil a good sample.
Laboratory procedures may vary. In one type Laboratory procedures may vary. In one type of test, a small sample of stool is placed on a of test, a small sample of stool is placed on a paper card. A drop or two of testing solution is paper card. A drop or two of testing solution is put on the opposite side of the card. A color put on the opposite side of the card. A color change indicates the presence of change indicates the presence of blood in the stoolblood in the stool..
Purpose: to detect pathological lesions (ex. Carcinoma) before they Purpose: to detect pathological lesions (ex. Carcinoma) before they produce symptoms and while the condition is still amenable to produce symptoms and while the condition is still amenable to treatment. treatment.
This testing is widely used in mass screening programs for This testing is widely used in mass screening programs for colorectal cancer. colorectal cancer. A number of easy-to-use test kits for detection of occult blood are A number of easy-to-use test kits for detection of occult blood are available. Prior to such kits, the traditional method was to expose available. Prior to such kits, the traditional method was to expose the sample to a sequence of solutions that included glacial acetic the sample to a sequence of solutions that included glacial acetic acid, gum guaiac solution and hydrogen peroxide. A blue color acid, gum guaiac solution and hydrogen peroxide. A blue color indicated a positive test result. The test kits use these same indicated a positive test result. The test kits use these same principles, with some using paper impregnated with guaiac. For principles, with some using paper impregnated with guaiac. For these reasons, analysis of feces for occult blood is sometimes still these reasons, analysis of feces for occult blood is sometimes still referred to as “stool for guaiac.”referred to as “stool for guaiac.”
One of the main problems of testing stools for occult blood is the One of the main problems of testing stools for occult blood is the number of false-positive results that occur. number of false-positive results that occur.
-diet in meat-diet in meat-diets high in certain vegetables (ex. horseradish, and turnips) and in -diets high in certain vegetables (ex. horseradish, and turnips) and in
bananas.bananas.-bleeding from the gums or nasal passages -bleeding from the gums or nasal passages -therapy with many drugs due to direct and indirect drug effects on the -therapy with many drugs due to direct and indirect drug effects on the
Black stools-associated with upper G.I. bleeding Black stools-associated with upper G.I. bleeding when the hemoglobin has come in contact with when the hemoglobin has come in contact with gastric acid and has been converted to hematin. gastric acid and has been converted to hematin. (5 days)(5 days)
Red/maroon—liquid consistency – upper G.I. Red/maroon—liquid consistency – upper G.I. bleeding is massive and the volume increases G.I. bleeding is massive and the volume increases G.I. motility motility
Bright red – lower G.I. bleeding from hemorrhoids, Bright red – lower G.I. bleeding from hemorrhoids, ulcerative colitis and carcinomas. ulcerative colitis and carcinomas.
Occult Blood Occult Blood indications/purposesindications/purposes-known or suspected disorder -known or suspected disorder
associated with gastrointestinal associated with gastrointestinal bleedingbleeding
-therapy with drugs that may lead to -therapy with drugs that may lead to gastrointestinal bleeding ex. Aspirin, gastrointestinal bleeding ex. Aspirin, anticoagulantsanticoagulants
Rectum and AnusRectum and AnusHemorrhoids Hemorrhoids
usual age of occurrence: older adults usual age of occurrence: older adults severity: usually mild; blood is bright redseverity: usually mild; blood is bright redother features: maybe painless or other features: maybe painless or
symptomatic often associated with symptomatic often associated with constipation.constipation.
Anorectal fissureAnorectal fissure• any ageany age• usually mild; blood is bright redusually mild; blood is bright red• nearly always painful. Crohn’s nearly always painful. Crohn’s
disease, anal intercourse may disease, anal intercourse may predisposepredispose
In the event of a positive fecal occult In the event of a positive fecal occult blood test, the next step in the blood test, the next step in the workup is a form of visualization of workup is a form of visualization of the gastrointestinal tract (ie: the gastrointestinal tract (ie: endoscopyendoscopy, , colonoscopycolonoscopy, , virtual colonoscopyvirtual colonoscopy).).
There are three methods for measuring There are three methods for measuring bloodblood in in fecesfeces::(Hemoccult or Instaccult). This method can reduce (Hemoccult or Instaccult). This method can reduce
death from colorectal cancer. death from colorectal cancer. Fecal Fecal porphyrinporphyrin quantification (Hemoquant) - high quantification (Hemoquant) - high
(HemeSelect), (QuickVue iFOB), (FOBGold or (HemeSelect), (QuickVue iFOB), (FOBGold or Automated SENTiFOB) or (OC Auto 80 - Automated Automated SENTiFOB) or (OC Auto 80 - Automated iFOBT) - more specific. iFOBT) - more specific.
Fecal DNA test (PreGen-Plus) is more sensitive than Fecal DNA test (PreGen-Plus) is more sensitive than fecal occult blood in one study (51.6% vs. 12.9%)fecal occult blood in one study (51.6% vs. 12.9%)
One methodOne method the test involves smearing some feces the test involves smearing some feces onto some absorbent paper that has onto some absorbent paper that has been treated with a chemical. been treated with a chemical. Hydrogen peroxideHydrogen peroxide is dropped onto the is dropped onto the paper; if trace amounts of paper; if trace amounts of bloodblood are are present, the paper will change color. present, the paper will change color. This method works as This method works as hemoglobinhemoglobin has has a a peroxidaseperoxidase-like effect, rapidly -like effect, rapidly breaking down hydrogen peroxide.breaking down hydrogen peroxide.
Fecal Immunochemical Fecal Immunochemical TestsTests These tests detect the These tests detect the globinglobin in in fecesfeces
rather than rather than hemeheme. By detecting . By detecting globin the tests are both more globin the tests are both more sensitive and specific for lower sensitive and specific for lower gastrointestinal bleedinggastrointestinal bleeding
InsureInsure is designed to address patient ease is designed to address patient ease of use by using a brush, not a of use by using a brush, not a wooden stick, to sample stools while wooden stick, to sample stools while in the toilet bowl. Using these tests in the toilet bowl. Using these tests there is no direct fecal handling and there is no direct fecal handling and there is no need for changing diet or there is no need for changing diet or medication to perform the test. medication to perform the test.
The Clearview iFOB test The Clearview iFOB test requires only one specimen, and because it is requires only one specimen, and because it is specific to human hemoglobin, patients are specific to human hemoglobin, patients are not required to adhere to strict dietary or not required to adhere to strict dietary or medication restrictions. For hospitals and medication restrictions. For hospitals and large clinics the OC Automated 80 can large clinics the OC Automated 80 can perform fecal occult blood detection by perform fecal occult blood detection by immunoassay. This method addresses the immunoassay. This method addresses the dietary issues associated with the guaiac test dietary issues associated with the guaiac test and has been shown to detect many more and has been shown to detect many more early stage cancers and polyps.early stage cancers and polyps.
guaiac-based fecal occult blood guaiac-based fecal occult blood test test
usually picks up a daily blood loss of about 10 ml (about usually picks up a daily blood loss of about 10 ml (about two teaspoonfuls). The sensitivity of a single FOBT has been two teaspoonfuls). The sensitivity of a single FOBT has been quoted at 30%, but if 3 tests are done (as is standard), the quoted at 30%, but if 3 tests are done (as is standard), the sensitivity rises to 92%. sensitivity rises to 92%.
"Normally, there is only about 0.5 to 1.5 ml of blood a day "Normally, there is only about 0.5 to 1.5 ml of blood a day that escapes blood vessels into the stool each day. There that escapes blood vessels into the stool each day. There are more sensitive tests than the guaiac such as a heme-are more sensitive tests than the guaiac such as a heme-porphyrin test or an immunochemical test, but the former porphyrin test or an immunochemical test, but the former test is not used much due to the high false positive rate. test is not used much due to the high false positive rate. The latter test is very sensitive -- it picks up as little as 0.3 The latter test is very sensitive -- it picks up as little as 0.3 ml... It does not detect blood from the stomach and upper ml... It does not detect blood from the stomach and upper small intestine so it is much more specific for bleeding from small intestine so it is much more specific for bleeding from the colon or lower gastrointestinal tract."the colon or lower gastrointestinal tract."
PreGen-Plus PreGen-Plus The stool-based DNA test, was The stool-based DNA test, was capable of detecting several stages capable of detecting several stages of colorectal cancer, in otherwise of colorectal cancer, in otherwise healthy adults, and most importantly healthy adults, and most importantly in its' early stage, the easiest and in its' early stage, the easiest and most effective to treat, stage of most effective to treat, stage of colorectal cancer.colorectal cancer.
How the Test is How the Test is PerformedPerformed
There is no direct handling of stool with this test. There is no direct handling of stool with this test. You simply note any changes on a card and then You simply note any changes on a card and then mail the results card to your physician.mail the results card to your physician.
Urinate if you need to, then flush the toilet before Urinate if you need to, then flush the toilet before you defecate. After the bowel movement, place you defecate. After the bowel movement, place the chemically treated tissue pad in the toilet. the chemically treated tissue pad in the toilet. Watch for a change of color on the test area of the Watch for a change of color on the test area of the pad (results usually appear within two minutes). pad (results usually appear within two minutes). Note the results on the card provided, then flush Note the results on the card provided, then flush the pad away. Repeat for the next two consecutive the pad away. Repeat for the next two consecutive bowel movements.bowel movements.
Causes for a positive test are:Causes for a positive test are:• 2-10%: cancer (colorectal cancer, 2-10%: cancer (colorectal cancer,
gastric cancer) gastric cancer) • 20-30% adenoma or polyps 20-30% adenoma or polyps • Bleeding peptic ulcer Bleeding peptic ulcer • Angiodysplasia of the colon Angiodysplasia of the colon
