Fecal occult blood 643768 225935994 2008-07-16T02:37:09Z Kubigula 1453997 Reverted edits by [[Special:Contributions/203.37.206.217|203.37.206.217]] to last version by Jehochman (using [[WP:HG|Huggle]]) {{Infobox_Disease | Name = Fecal occult blood | Image = | Caption = | DiseasesDB = 30751 | ICD10 = {{ICD10|R|19|5|r|10}} | ICD9 = {{ICD9|792.1}} | ICDO = | OMIM = | MedlinePlus = 007008 | eMedicineSubj = | eMedicineTopic = | MeshID = D009780 | }} '''Fecal occult blood''' is a term for [[blood]] present in the [[feces]] that is not visibly apparent. In [[medicine]], a '''fecal occult blood test''' is a check for hidden (occult) [[blood]] in the stool ([[feces]]). Conventional fecal occult blood tests look for [[heme]]. Newer, modern tests look for [[globin]]. ==Uses== Fecal occult blood testing - as its name implies - can provide clues as to subtle blood loss in the [[gastrointestinal tract]], anywhere from the [[mouth]] to the [[colon (anatomy)|colon]]. Positive tests ("positive stool") warrant further investigation for [[peptic ulcer]]s or a [[malignancy]] (such as [[colorectal cancer]] or [[gastric cancer]]). In the event of a positive fecal occult blood test, the next step in the workup is a form of visualization of the gastrointestinal tract (ie: [[endoscopy]], [[colonoscopy]], [[virtual colonoscopy]]). Annual testing of a population may reduce the mortality associated with colon cancer by a third, depending on the incidence of gastrointestinal cancer in that population. It is not always cost effective to [[Screening (medicine)|screen]] a large population. If colon cancer is suspected in an individual (such as in someone with an unexplained [[anaemia]]) fecal occult blood tests are typically not warranted. If a doctor suspects colon cancer, more rigorous investigation is necessary, whether or not the test is positive. ==Methodology== For a simple, traditional test, foods to avoid include red meat (the blood it contains can turn the test positive), radishes, turnips, cabbage, cauliflower, horseradish, uncooked broccoli, and cantaloupe (all of which contain a chemical that can turn the test positive), and citrus fruits and vitamin C supplements (which can turn the test falsely negative).<ref>{{cite web |url=http://www.health.harvard.edu/diagnostic-tests/fecal-occult-blood-test.htm |title=Diagnostic Tests — Fecal Occult Blood Test |accessdate=2007-07-18 |format= |work=}}</ref> Checking for hidden (occult) blood in the stool can be done at home. Testing kits are available at pharmacies without a prescription, or a health professional may order a testing kit for use at home. If a home fecal occult blood test detects blood in the stool, a health professional should be contacted.<ref>{{cite web |url=http://www.webmd.com/colorectal-cancer/Fecal-Occult-Blood-Test-FOBT |title=Fecal Occult Blood Test (FOBT) |accessdate=2007-07-18 |format= |work=}}</ref> There are three methods for measuring [[blood]] in [[feces]]: * (Hemoccult or Instaccult). This method can reduce death from colorectal cancer. * Fecal [[porphyrin]] quantification (Hemoquant) - high [[Type I and type II errors|false positive]] rate. * Immunochemical fecal occult blood tests (HemeSelect), (QuickVue iFOB), (FOBGold or Automated SENTiFOB) or (OC Auto 80 - Automated iFOBT) - more specific. * Fecal DNA test (PreGen-Plus) is more sensitive than fecal occult blood in one study (51.6% vs. 12.9%)<ref name="pmid15616205">{{cite journal | author = Imperiale T, Ransohoff D, Itzkowitz S, Turnbull B, Ross M | title = Fecal DNA versus fecal occult blood for colorectal-cancer screening in an average-risk population | journal = N Engl J Med | volume = 351 | issue = 26 | pages = 2704–14 | year = 2004 | pmid = 15616205 | doi = 10.1056/NEJMoa033403}}</ref> ''One method:'' the test involves smearing some feces onto some absorbent paper that has been treated with a chemical. [[Hydrogen peroxide]] is dropped onto the paper; if trace amounts of [[blood]] are present, the paper will change color. This method works as [[hemoglobin]] has a [[peroxidase]]-like effect, rapidly breaking down hydrogen peroxide. Since 2001, there are a new class of occult blood tests called Fecal Immunochemical Tests. These tests detect the [[globin]] in [[feces]] rather than [[heme]]. By detecting [[globin]] the tests are both more sensitive and specific for [[lower gastrointestinal bleeding]]. == Sensitivity == The common, traditional guaiac-based fecal occult blood test usually picks up a daily blood loss of about 10 ml (about two teaspoonfuls). The sensitivity of a single FOBT has been quoted at 30%, but if 3 tests are done (as is standard), the sensitivity rises to 92%. <ref>{{cite web |url=http://www.uptodate.com/ |title=Screening average risk patients for colorectal cancer - B01 |accessdate=2007-10-25 |format= |work=}}</ref> "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 are more sensitive tests than the guaiac such as a heme-porphyrin test or an immunochemical test, but the former 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 ml... It does not detect blood from the stomach and upper small intestine so it is much more specific for bleeding from the colon or lower gastrointestinal tract."<ref>{{cite web |url=http://www.wdxcyber.com/ncanc10.htm |title=What Does a Positive Fecal Occult Blood Test Mean? - B01 |accessdate=2007-07-18 |format= |work=}}</ref> == Interpretation == The test is often [[Type I and type II errors|false-positive]] (i.e. there is no source of bleeding). This is often due to recent ingestion of under-cooked meats, and a patient is generally advised to keep a [[Vegetarianism|meat-free diet]] for several days before handing in the feces sample. [[Type I and type II errors|False negative]]s may result if the patient has been taking [[vitamin C]] supplements. The test is more sensitive if the sample is hydrated before testing. However, the specificity is decreased in this method. Newer, more sophisticated assays called Fecal Immunochemical Tests have been developed to address most of the deficiencies of traditional guaiac based fecal occult blood tests. The stool-based DNA test, PreGen-Plus was capable of detecting several stages of colorectal cancer, in otherwise healthy adults, and most importantly in its' early stage, the easiest and most effective to treat, stage of colorectal cancer. == Results == The DNA based PreGen-Plus's results were reported by the New England Journal of Medicine see their website for more.<ref>[http://www.mi3.com/pressreleases/2004.12.22.Exact.pdf] for the DNA based PreGen-Plus information sheet from The New England Journal of Medicine.</ref> An estimated 1-5% of the tested population have a positive fecal occult blood test. Of those, about 2-10% have cancer, while 20-30% have [[adenoma]]s. Causes for a positive test are: * 2-10%: [[cancer]] ([[colorectal cancer]], [[gastric cancer]]) * 20-30% adenoma or [[Polyp (medicine)|polyp]]s * Bleeding [[peptic ulcer]] * [[Angiodysplasia]] of the colon ==References== <references/> == External links== * {{FPnotebook|GI147}} ==See also== * [[Blood in stool]] * [[Digital rectal examination]] ==External links== * [http://www.mayoclinic.com/health/fecal-occult-blood-test/SA00002 Overview] at [[Mayo Clinic]] * [http://www.clevelandclinic.org/health/health-info/docs/1700/1788.asp?index=7143 Overview] at [[Cleveland Clinic]] {{Digestive system and abdomen symptoms and signs}} [[Category:Diagnostic gastroenterology]] [[Category:Blood tests]] [[Category:Feces|Feces]] [[Category:Stool tests]] [[de:Guajak-Test]] [[fr:Saignement occulte]] [[he:דם סמוי בצואה]] [[pl:Test na krew utajoną w kale]] [[ur:برازی خون مخفی]]