Inpatient Service Day 6! Which means my 6th consecutive #MedThread of this #BreadNButterMedicine series.
Today's topic: Utility of Fecal Occult Blood Testing (FOBT) in the inpatient setting.
TL;DR - You probably shouldn't be doing them.pic.twitter.com/N7BJ5CwoJ8
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2/ (Poll) Do you ROUTINELY order FOBT as an inpatient test?
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3/ As always, let's dive a little into the background of what FOBT testing is. This is a test that was developed for and then traditionally used in outpatient colorectal cancer (CRC) screening. If used as screening the USPSTF recommends screening annually. https://www.uspreventiveservicestaskforce.org/Page/Document/RecommendationStatementFinal/colorectal-cancer-screening2#tab …pic.twitter.com/TSGnvyUWSY
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4/ There are two types of testing which most consider FOBT.
gFOBT is Guiac-based testing that tests for the heme component of hemoglobin.
FIT is an immunochemical test for the globin component of hemoglobinpic.twitter.com/k6vYBShIy91 reply 0 retweets 2 likesShow this thread -
5/ gFOBT works by detecting pseudoperoxidase in hemoglobin. A positive result occurs if the testing paper containing a stool specimen turns blue after adding the developer. https://en.wikipedia.org/wiki/Stool_guaiac_test …pic.twitter.com/QNyg94bMfN
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6/ The active component of guaiac paper is alpha-guaiaconic acid and the active component of the developer is hydrogen peroxide. If a fecal sample contains hemoglobin, the peroxidase activity of heme catalyzes a reaction to form a blue colored quinone within a few seconds.pic.twitter.com/VPayX04RNp
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7/ FIT uses antibodies detecting the globin component of hemoglobin instead of heme like the gFOBT. Globin is broken down and decreased during intestinal transit by digestive enzymes and gastric acid and therefore FIT testing is more specific for lower GI bleeding.
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8/ Unfortunately gFOBT can produce false results. False Positives for CRC can be caused by medications that cause clinically insignificant GI blood loss (ASA, NSAIDs, EtOH), iron supplements, red meat & veggies like broccoli/cauliflower (due to peroxidase or catalase activity).pic.twitter.com/TEluORvjt2
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9/ False Negatives can be caused by Vitamin C



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10/ Here's a more comprehensive table that presents the causes of inaccurate FOBT. (I don't remember where I got this table for citation, sorry)pic.twitter.com/luxjpQRPTb
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great table! "FOBT false" ->https://www.grepmed.com/images/4851
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