Fecal immunochemical test
{{Short description|Diagnostic test for colorectal cancer}}
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The fecal immunochemical test (FIT) is a diagnostic technique that examines stool samples for traces of non-visible blood, which could potentially indicate conditions including bowel cancer.{{cite web |title=Bowel Cancer: Testing for blood in your poo using the FIT test|publisher= Cancer Research UK |url=https://www.cancerresearchuk.org/about-cancer/bowel-cancer/getting-diagnosed/tests/FIT|date= 6 December 2021}} Symptoms which could be caused by bowel cancer and suggest a FIT include a change in bowel habit, anaemia, unexplained weight loss, and abdominal pain.{{cite journal | last1=Quintero | first1=Enrique | last2=Castells | first2=Antoni | last3=Bujanda | first3=Luis | last4=Cubiella | first4=Joaquín | last5=Salas | first5=Dolores | last6=Lanas | first6=Ángel | last7=Andreu | first7=Montserrat | last8=Carballo | first8=Fernando | last9=Morillas | first9=Juan Diego | last10=Hernández | first10=Cristina | last11=Jover | first11=Rodrigo | last12=Montalvo | first12=Isabel | last13=Arenas | first13=Juan | last14=Laredo | first14=Eva | last15=Hernández | first15=Vicent | last16=Iglesias | first16=Felipe | last17=Cid | first17=Estela | last18=Zubizarreta | first18=Raquel | last19=Sala | first19=Teresa | last20=Ponce | first20=Marta | last21=Andrés | first21=Mercedes | last22=Teruel | first22=Gloria | last23=Peris | first23=Antonio | last24=Roncales | first24=María-Pilar | last25=Polo-Tomás | first25=Mónica | last26=Bessa | first26=Xavier | last27=Ferrer-Armengou | first27=Olga | last28=Grau | first28=Jaume | last29=Serradesanferm | first29=Anna | last30=Ono | first30=Akiko | last31=Cruzado | first31=José | last32=Pérez-Riquelme | first32=Francisco | last33=Alonso-Abreu | first33=Inmaculada | last34=de la Vega-Prieto | first34=Mariola | last35=Reyes-Melian | first35=Juana Maria | last36=Cacho | first36=Guillermo | last37=Díaz-Tasende | first37=José | last38=Herreros-de-Tejada | first38=Alberto | last39=Poves | first39=Carmen | last40=Santander | first40=Cecilio | last41=González-Navarro | first41=Andrés |display-authors=3| title=Colonoscopy versus Fecal Immunochemical Testing in Colorectal-Cancer Screening | journal=New England Journal of Medicine | publisher=Massachusetts Medical Society | volume=366 | issue=8 | date=23 February 2012 | issn=0028-4793 | doi=10.1056/nejmoa1108895 |doi-access=free| pages=697–706| pmid=22356323 | hdl=10486/663879 | hdl-access=free }}{{cite web |title=Fecal immunochemical test (FIT): MedlinePlus Medical Encyclopedia |url=https://medlineplus.gov/ency/patientinstructions/000704.htm |website=medlineplus.gov |language=en}} By using a random forest classification model, sensitivity can be increased.{{cite journal |last1=Baxter |first1=Nielson T. |last2=Ruffin |first2=Mack T. |last3=Rogers |first3=Mary A. M. |last4=Schloss |first4=Patrick D. |title=Microbiota-based model improves the sensitivity of fecal immunochemical test for detecting colonic lesions |journal=Genome Medicine |date=December 2016 |volume=8 |issue=1 |page=37 |doi=10.1186/s13073-016-0290-3|doi-access=free |pmid=27056827 |pmc=4823848 |hdl=2027.42/134551 |hdl-access=free }}
Blood in stools does not always mean the presence of bowel or anal cancer, it could be from other bowel diseases such as ulcerative colitis, Crohn's disease or even hemorrhoids.
A 2022 UK guideline for patients with signs or symptoms of suspected colorectal cancer recommends the use of a FIT threshold of faecal haemoglobin ≥10 μg Hb/g to select patients with symptoms for an urgent referral for colorectal cancer investigation.{{cite journal | last1=Monahan | first1=Kevin J | last2=Davies | first2=Michael M | last3=Abulafi | first3=Muti | last4=Banerjea | first4=Ayan | last5=Nicholson | first5=Brian D | last6=Arasaradnam | first6=Ramesh | last7=Barker | first7=Neil | last8=Benton | first8=Sally | last9=Booth | first9=Richard | last10=Burling | first10=David | last11=Carten | first11=Rachel Victoria | last12=D'Souza | first12=Nigel | last13=East | first13=James Edward | last14=Kleijnen | first14=Jos | last15=Machesney | first15=Michael | last16=Pettman | first16=Maria | last17=Pipe | first17=Jenny | last18=Saker | first18=Lance | last19=Sharp | first19=Linda | last20=Stephenson | first20=James | last21=Steele | first21=Robert JC|display-authors=3 | title=Faecal immunochemical testing (FIT) in patients with signs or symptoms of suspected colorectal cancer (CRC): a joint guideline from the Association of Coloproctology of Great Britain and Ireland (ACPGBI) and the British Society of Gastroenterology (BSG) | journal=Gut| volume=71 | issue=10 | date=12 July 2022 | issn=0017-5749 | doi=10.1136/gutjnl-2022-327985|doi-access=free| pages=1939–1962| pmid=35820780 | pmc=9484376 | hdl=10044/1/100510 | hdl-access=free }}