View source for Immunochemical test for blood in feces

[[File:FOBT positivity - Guaiac test x immunochemistry.jpg|thumb|right|FOBT positivity - Guaiac test x immunochemistry]]
'''Immunochemical detection of blood in the stool (iFOBT)''' is intended, unlike the screening [[Haemoccult|guaiac test]] (Haemoccult, gFOBT), to rule out bleeding into the GIT. The test is based on [[Immunochemistry|immunochemical]] detection of [[hemoglobin]] in reactions with [[Monoclonal antibodies|monoclonal antibody]] against human hemoglobin. Sensitivity and positive identification is also significantly affected by the different degradation of both components of hemoglobin with respect to the proximodistal gradient in the [[Digestive system|digestive system]]. Globin is degraded much more rapidly, and a positive immunochemical test almost eliminates the detection of bleeding in the upper part of the alimentary canal. Hemagglutination, latex immunoprecipitation, radial immunodiffusion and immunoaffinity [[chromatography]] tests are based on the immunochemical principle. Detection of the protein (human hemoglobin) [[Monoclonal antibodies|monoclonal antibody]] excludes the possibility of being affected by another source of hemoglobin (food), the interference of chemical substances is eliminated, and a special diet is not necessary. The sensitivity of immunochemical tests is significantly higher; depending on the technique and < 0.1 mg hemoglobin/g stool. Immunochemical tests include, for example, the latex Hemolex test, Heme-Select based on the principle of reverse passive hemagglutination, ImmoCare immunoaffinity chromatography, Dialab FOB test, Hexagon OBTI, Actim test and others.

== Test Execution ==
[[File:Immunochemical tests - FOBT.jpg|thumb|right|Immunochemical tests - FOBT]]
Immunochemical tests vary significantly according to the type of technique used. Recently, the most widespread variant is immunoaffinity [[chromatography]]. The patient collects 1 stool sample in a collection container with a stabilizing solution. However, [[Stool examination|Stool sampling]] involves a significant risk of preanalytical error. Laboratory processing consists of applying a drop of extract to the test and reading 1 or 2 colored strips that detect the presence of only the antibody with a colored marker (negative test, 1 colored strip) or the formation of an antigen-antibody complex (positive test, 2 colored strips). The evaluation is again only qualitative.

Studies have been testing several immunochemical analyzers for [[quantitative determination of hemoglobin in stool]] (qi-FOBT) in recent years, most of which are of Japanese manufacture. ROC curves demonstrate a specificity for advanced [[adenomas]]s of 95.3% at a sensitivity of 100 ng Hb/mL. 
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== Links ==
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[[Category:Gastroenterology]]
[[Category:Internal Medicine]]
[[Category:General practice medicine]]