Stool guaiac test

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.{{cite journal |vauthors=Beg M, etal |title=Occult Gastrointestinal Bleeding: Detection, Interpretation, and Evaluation |journal=JIACM |volume=3 |issue=2 |pages=153–8 |year=2002 |url=http://medind.nic.in/jac/t02/i2/jact02i2p153.pdf |access-date=2010-10-26 |archive-date=2010-11-22 |archive-url=https://web.archive.org/web/20101122112908/http://medind.nic.in/jac/t02/i2/jact02i2p153.pdf }}

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 is obtained by catching the stool and transferring a sample with an applicator. Digital rectal examination specimens are also used but this method is discouraged for colorectal cancer screening due to very poor performance characteristics.

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.{{citation needed|date=January 2022}}

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.{{citation needed|date=January 2022}}

When the hydrogen peroxide is dripped on to the guaiac paper, it oxidizes the alpha-guaiaconic acid to a blue colored quinone.{{cite journal |vauthors=Kratochvil JF, etal |title=Isolation and characterization of alpha-guaiaconic acid and the nature of guiacum blue |journal=Phytochemistry |volume=10 |issue=10 |pages=2529–2531 |year=1971 |doi=10.1016/s0031-9422(00)89901-x|bibcode=1971PChem..10.2529K }}{{cite web|last1=Guthlein |first1=W. |last2=Wielinger |first2=H.|last3= Rittersdorf |first3=W.|last4= Werner |first4=W.|title= Guaiaconic acid A from guaiac resin, US Patent 4297271 |website=Free Patents Online |date=27 October 1981 |format=PDF |url= http://www.freepatentsonline.com/4297271.html}} 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.

image:Possible Guaiacum blue formation reactions.svg

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.{{cite journal |vauthors=Jaffe RM, Kasten B, Young DS, MacLowry JD |title=False-negative stool occult blood tests caused by ingestion of ascorbic acid (vitamin C) |journal=Annals of Internal Medicine |volume=83 |issue=6 |pages=824–6 |date=December 1975 |pmid=1200528 |doi=10.7326/0003-4819-83-6-824}}{{cite journal |vauthors=Garrick DP, Close JR, McMurray W |title=Detection of occult blood in faeces |journal=Lancet |volume=2 |issue=8042 |pages=820–1 |date=October 1977 |pmid=71626 |doi= 10.1016/S0140-6736(77)90753-X|s2cid=5822559 }}

If the card has not been promptly developed, the water content of the feces decreases, and this can reduce the detection of blood.{{cite journal |vauthors=Ahlquist DA, McGill DB, Schwartz S, Taylor WF, Owen RA |title=Fecal blood levels in health and disease. A study using HemoQuant |journal=N. Engl. J. Med. |volume=312 |issue=22 |pages=1422–8 |date=May 1985 |pmid=3873009 |doi=10.1056/NEJM198505303122204 }} Although rehydration of stored samples can reverse this effect{{cite journal |vauthors=Wells HJ, Pagano JF |title=Hemoccult test — reversal of false-negative results due to storage |journal=Gastroenterology |volume=72 |page=1148 |year=1977 }} this is not recommended because the test becomes unduly analytically sensitive and thus much less specific.{{cite journal |vauthors=Macrae FA, St John DJ |title=Relationship between patterns of bleeding and Hemoccult sensitivity in patients with colorectal cancers or adenomas |journal=Gastroenterology |volume=82 |issue=5 Pt 1 |pages=891–8 |date=May 1982 |doi=10.1016/S0016-5085(82)80252-7 |pmid=7060910 |doi-access=free }}{{cite journal |vauthors=Frame PS, Kowulich BA |title=Stool occult blood screening for colorectal cancer |journal=J Fam Pract |volume=15 |issue=6 |pages=1071–5 |date=December 1982 |pmid=7142926 }}

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 questionably green to blue, such samples are designated positive.{{cite web|title=Michigan Regional Laboratory System. Fecal occult blood|date= August 2007|access-date= October 26, 2010|url= https://docs.google.com/viewer?url=http://www.michigan.gov/documents/Prhemocl_25742_7.wpd__PR_Hemeoccult_bld_in_feces_proc.doc}}

The package insert guidelines from the manufacturers, for example Hemoccult SENSA,{{Cite web|url=https://docs.google.com/viewer?url=http://www.beckmancoulter.com/literature/ClinDiag/462489.E.pdf|title=None}} 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,{{cite journal |vauthors=Grossman MI, Matsumoto KK, Lichter RJ |title=Fecal blood loss produced by oral and intravenous administration of various salicylates |journal=Gastroenterology |volume=40 |issue=3 |pages=383–8 |date=March 1961 |pmid=13709097 |doi=10.1016/S0016-5085(61)80070-X }}{{cite journal |vauthors=Pierson RN, Holt PR, Watson RM, Keating RP |title=Aspirin and gastrointestinal bleeding. Chromate blood loss studies |journal=Am. J. Med. |volume=31 |issue=2 |pages=259–65 |date=August 1961 |pmid=13735596 | doi = 10.1016/0002-9343(61)90114-0 }} but there is some doubt about how frequently this occurs with NSAID medication.{{cite journal |author=Norfleet RG |title=1,300 mg of aspirin daily does not cause positive fecal hemoccult tests |journal=J. Clin. Gastroenterol. |volume=5 |issue=2 |pages=123–5 |date=April 1983 |pmid=6304182 |doi=10.1097/00004836-198304000-00006}}{{cite journal |vauthors=Doubilet P, Donowitz M, Pauker SG |title=Evaluation for colon cancer in patients with occult fecal blood loss while taking aspirin: a Bayesian viewpoint |journal=Med Decis Making |volume=2 |issue=2 |pages=147–60 |year=1982 |pmid=7167043 |doi=10.1177/0272989x8200200206|s2cid=39268097 }}{{cite journal |vauthors=Bahrt KM, Korman LY, Nashel DJ |title=Significance of a positive test for occult blood in stools of patients taking anti-inflammatory drugs |journal=Arch. Intern. Med. |volume=144 |issue=11 |pages=2165–6 |date=November 1984 |pmid=6333854 |doi= 10.1001/archinte.144.11.2165}} 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.{{cite journal |vauthors=Laine LA, Bentley E, Chandrasoma P |title=Effect of oral iron therapy on the upper gastrointestinal tract. A prospective evaluation |journal=Dig. Dis. Sci. |volume=33 |issue=2 |pages=172–7 |date=February 1988 |pmid=3257437 |doi= 10.1007/BF01535729|s2cid=10139402 }}{{cite journal |vauthors=Anderson GD, Yuellig TR, Krone RE |title=An investigation into the effects of oral iron supplementation on in vivo Hemoccult stool testing |journal=Am. J. Gastroenterol. |volume=85 |issue=5 |pages=558–61 |date=May 1990 |pmid=2186616 }}

There is no consensus on whether to stop warfarin before a guaiac test.{{cite journal |author=Imperiale TF |title=Continue or discontinue warfarin for fecal occult blood testing in 2010? Does the published evidence provide an answer? |journal=Am. J. Gastroenterol. |volume=105 |issue=9 |pages=2036–9 |date=September 2010 |pmid=20818354 |doi=10.1038/ajg.2010.269 |s2cid=22003870 }} 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.{{cite journal |vauthors=Jaffin BW, Bliss CM, LaMont JT |title=Significance of occult gastrointestinal bleeding during anticoagulation therapy |journal=Am. J. Med. |volume=83 |issue=2 |pages=269–72 |date=August 1987 |pmid=3497580 |doi= 10.1016/0002-9343(87)90697-8}}{{cite journal |vauthors=Barada K, Abdul-Baki H, El Hajj II, Hashash JG, Green PH |title=Gastrointestinal bleeding in the setting of anticoagulation and antiplatelet therapy |journal=J. Clin. Gastroenterol. |volume=43 |issue=1 |pages=5–12 |date=January 2009 |pmid=18607297 |doi=10.1097/MCG.0b013e31811edd13 |s2cid=25371088 }}

The article fecal occult blood (FOB) provides an expanded consideration of the clinical application of FOB tests generally, including other clinical methods, and the comments here are those that relate specifically to the guaiac gFOBT method.

One major use of stool testing for blood is detection of colorectal cancer. However, other possible positive results include: gastroesophageal cancer, GI bleeds, diverticulae, hemorrhoids, anal fissures, colon polyps, ulcerative colitis, Crohn's disease, celiac disease, GERD, esophagitis, peptic ulcers, gastritis, inflammatory bowel disease, vascular ectasias, portal hypertensive gastropathy, aortoenteric fistulas, hemobilia, endometriosis, and trauma.

The stool guaiac test was originally the principal colon cancer screening technology available, but modern tests which look for globin or DNA are now also available. Several recent colon cancer screening guidelines have recommended replacing any older low-sensitivity, guaiac-based fecal occult blood testing (gFOBT) with either newer high-sensitivity guaiac-based fecal occult blood testing (gFOBT) or fecal immunochemical testing (FIT), which tests for globin rather than the heme detected by the guaiac method. The US Multisociety Task Force (MSTF) looked at 6 studies that compared high sensitivity gFOBT (Hemoccult SENSA) to FIT, and concluded that there were no clear difference in overall performance between these methods,{{cite journal |vauthors=Levin B, Lieberman DA, McFarland B, etal |title=Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology |journal=Gastroenterology |volume=134 |issue=5 |pages=1570–95 |date=May 2008 |pmid=18384785 |doi=10.1053/j.gastro.2008.02.002 |url=http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1044&context=veterans |doi-access=free |url-access=subscription }} Also published as {{cite journal |author1=Levin B |author2=Lieberman DA |author3=McFarland B | year = 2008 | title = Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology| url = http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1044&context=veterans| journal = CA Cancer J Clin | volume = 58 | issue = 3| pages = 130–60 | doi = 10.3322/CA.2007.0018 | pmid = 18322143 |s2cid=8199010 |display-authors=etal| doi-access = free }} and a similar recommendation was made by the National Guideline Clearinghouse (NGC).{{Cite web|url=http://www.guideline.gov/content.aspx?id=14345|archive-url=https://archive.today/20120802154144/http://www.guideline.gov/content.aspx?id=14345|url-status=dead|archive-date=2012-08-02|title=National Guideline Clearinghouse | Colorectal cancer screening clinic…|date=August 2, 2012}}

Results of a single fecal sample should be interpreted cautiously, as there is a high rate of false negativity associated with the test.{{Cite web |url=http://www.practicalgastro.com/pdf/June07/June07AllisonArticle.pdf |title=Archived copy |access-date=2010-07-18 |archive-date=2010-11-21 |archive-url=https://web.archive.org/web/20101121190959/http://www.practicalgastro.com/pdf/June07/June07AllisonArticle.pdf }}{{cite journal |vauthors=Collins JF, Lieberman DA, Durbin TE, Weiss DG |title=Accuracy of screening for fecal occult blood on a single stool sample obtained by digital rectal examination: a comparison with recommended sampling practice |journal=Annals of Internal Medicine |volume=142 |issue=2 |pages=81–5 |date=January 2005 |pmid=15657155 |doi=10.7326/0003-4819-142-2-200501180-00006|url=http://www.vaoutcomes.org/papers/DRE_CSP_final.pdf|citeseerx=10.1.1.580.829 |s2cid=29833684 }} Using three cards, each on a different day, is recommended to improve sensitivity.{{cite web |url=http://www.uptodate.com/ |title=Screening average risk patients for colorectal cancer — B01 |access-date=2007-10-25 }} The Centers for Disease Control and Prevention (CDC) in a 2006–2007 survey found extensive inappropriate use of low sensitivity gFOBT and of single specimens; it is unclear if these widespread suboptimal approaches have since declined.{{cite journal |vauthors=Nadel MR, Berkowitz Z, Klabunde CN, Smith RA, Coughlin SS, White MC |title=Fecal occult blood testing beliefs and practices of U.S. primary care physicians: serious deviations from evidence-based recommendations |journal=J Gen Intern Med |volume=25 |issue=8 |pages=833–9 |date=August 2010 |pmid=20383599 |pmc=2896587 |doi=10.1007/s11606-010-1328-7 }} The Current Procedural Terminology (CPT) coding was changed in January 2006 to include CPT code 82270, which indicates that consecutive collection of three stool samples has occurred, either as three single cards or a single triple card. Since January 2007, the US Medicare program reimburses for colorectal cancer screening with gFOBT only when this code is used.Centers for Medicare and Medicaid Services. Colorectal cancer: Preventable, treatable and beatable: Medicare coverage and billing for colorectal cancer screening. Medicare Learning Network Matters SE0710. [http://www.cms.hhs.gov/MLNMattersArticles/downloads/SE0710.pdf www.cms.hhs.gov/MLNMattersArticles/downloads/SE0710.pdf] Accessioned 2010 November 1

The stool guaiac test method may be preferable to fecal immunochemical testing (FIT) if there is a clinical concern about possible gastric or proximal upper intestinal bleeding.{{cite journal |author=Rockey DC |title=Occult gastrointestinal bleeding |journal=N. Engl. J. Med. |volume=341 |issue=1 |pages=38–46 |date=July 1999 |pmid=10387941 |doi=10.1056/NEJM199907013410107 }} However, although heme breakdown is less than globin during intestinal transit, false negative results can be seen with the stool guaiac tests due to degradation of the peroxidase-activity. This can cause false negative results in upper gastrointestinal bleeding sources, or in right colon adenomas and cancers that have comparable blood losses to positively testing left colon lesions.{{cite journal |vauthors=Herzog P, Holtermüller KH, Preiss J, etal |title=Fecal blood loss in patients with colonic polyps: a comparison of measurements with 51chromium-labeled erythrocytes and with the Haemoccult test |journal=Gastroenterology |volume=83 |issue=5 |pages=957–62 |date=November 1982 |doi=10.1016/S0016-5085(82)80061-9 |pmid=7117808 |doi-access=free }} A positive gFOBT with subsequent negative colonoscopy may lead to an upper endoscopy.{{cite journal |author=Rockey DC |title=Occult gastrointestinal bleeding |journal=Gastroenterol. Clin. North Am. |volume=34 |issue=4 |pages=699–718 |date=December 2005 |pmid=16303578 |doi=10.1016/j.gtc.2005.08.010 }} It is unclear whether this is an effective intervention if there is a positive gFOBT but no anemia.{{cite journal |vauthors=Zappa M, Visioli CB, Ciatto S, etal |title=Gastric cancer after positive screening faecal occult blood testing and negative assessment |journal=Dig Liver Dis |volume=39 |issue=4 |pages=321–6 |date=April 2007 |pmid=17314076 |doi=10.1016/j.dld.2006.11.010 }}{{cite journal |author=Bond JH |title=FOBT is not an effective way to screen for gastric cancer |journal=Dig Liver Dis |volume=39 |issue=4 |pages=327–8 |date=April 2007 |pmid=17317346 |doi=10.1016/j.dld.2006.12.013 }}{{cite journal |vauthors=Allard J, Cosby R, Del Giudice ME, Irvine EJ, Morgan D, Tinmouth J |title=Gastroscopy following a positive fecal occult blood test and negative colonoscopy: systematic review and guideline |journal=Can. J. Gastroenterol. |volume=24 |issue=2 |pages=113–20 |date=February 2010 |pmid=20151070 |pmc=2852233|doi=10.1155/2010/516363 |doi-access=free }} Endoscopy when there is a positive gFOBT along with iron deficiency anemia, or iron deficiency anemia on its own, has a higher rate of finding problems.{{Citation needed|date=November 2010}}

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Category:Diagnostic gastroenterology

Category:Stool tests

Category:Feces