Ryan Patrick Radecki, MD, MS, is an emergency physician and informatician with Christchurch Hospital in Christchurch,
New Zealand. He is the Annals of Emergency
Medicine podcast co-host and Journal Club editor and can be found on Twitter @emlitofnote.
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7 Responses to “It’s Time to Abandon Fecal Occult Blood Testing in the Emergency Department”
September 15, 2019
LarryPseudo science here. This test has saved me and my patients hundreds of times over the years. Really wish this article was better vetted before publication.
September 15, 2019
Chris WiesnerThe sensitivity of FOBT for malignancy (which is dependent on whether the malignancy is bleeding in addition to actual FOBT performance) is irrelevant for ED performance and value.
You misreported the study results on serial ingestion of blood and subsequent detection when you said “only one of 12 study subjects resulted a positive guaiac-based test”. Each of the 10 patients (not 12) had three serial stool samples. After ingesting 15 ml of blood the guaiac-based test was positive in at least one stool sample in six out of 10 subjects (60%). However, in only one patient was the guaiac-based test positive in all three of that patient’s stool samples. The study abstract doesn’t detail which samples were positive (it would be interesting to know if the timing mattered — i.e., were all the positives in samples collected later).
You wrote that one study “found profound mismatch between test results and follow-up endoscopy”. The study you cite (reference #7) evaluated the use of FOBT in hospital inpatients to detect colonic malignancies. Only 41% of patients with a positive FOBT were even referred to GI and colonoscopy to evaluate for malignancy was performed in 28%. How does a study that doesn’t even include upper endoscopy and is in an entirely irrelevant patient population have relevance to ED use? And saying “follow-up endoscopy” rather than “follow-up colonoscopy” is, bluntly, misleading.
My gastoenterologists generally ask about, are interested in, and act on guaiac test results in the appropriate clinical situation.
Certainly the performance characteristics as well as false positives and negatives are an issue. But no test is perfect, and the limited noninvasive surrogates — like the BUN/Cr ratio — surely aren’t better. Bringing up issues like not being able to withhold certain foods or the possibility of epistaxis being a confounder is silly. We are not screening every patient with a rectal exam and FOBT — the test should be used in appropriately selected patients in which case it can provide useful (if imperfect) clinical information.
FOBT testing can help distinguish between true melena and black stool caused by confounders like iron supplements. It can help confirm whether reported hematemesis at home was truly due to UGIB. It can infrequently be lifesaving in cases of unexplained syncope due to an occult GI bleed that later worsens. I’m aware of two malpractice suits that the MD settled because of syncope followed by death at home due to GI bleeding when a rectal exam and FOBT were not done.
September 15, 2019
Brian LevyOf course the gastroenterologists don’t like the test. They don’t like it because they would prefer that every single patient get sent for a colonoscopy that they will get to charge a fee for performing. The difficulty is that in many environments (where I practice it may take six months or a year for a patient to be seen for a scope, and the GI docs ho-hum in disbelief when they are told about cases, leaving the ER doc with the full burden of medicolegal risk. No, FOBT isn’t entirely sensitive, but in my experience, a positive is a genuine positive in almost every case.
September 30, 2019
Ryan Patrick RadeckiI appreciate the concerns of the various correspondents. It is indeed reasonable to raise concerns regarding the generalizability of the presented evidence with regard to FOBT and malignancy. However, to do so inadvertently supports the overall assertion of the piece regarding lack of evidence describing its validity as a test for Emergency Department use.
Need for clarifications are correctly illuminated in the citation regarding ingestion of blood, in which, ultimately, after ingesting 15mL of blood for three days, 6 of 10 subjects had at least one positive guaiac-based test. However, only 3 of 10 demonstrated two or more positive guaiac-based results, and only 1 of 10 demonstrated positive results on all three. Stated otherwise, it remains 20 of 30 samples demonstrated negative guaiac-based results while ingesting 15mL of blood daily.
Regarding the citation of the audit of inpatient use of FOBT, it is not misleading to characterize the results as a “profound mismatch”. Delving into the particulars of low-quality retrospective evidence provides easy targets for criticism, while this article simply observes the infrequency with which FOBT results were acted upon. Furthermore, when a subsequent gastrointestinal investigation was performed, it was more frequently an upper endoscopy than a colonoscopy, implying FOBT was not being performed primarily as colorectal cancer screening.
Anecdotal observations aside, it is clear relying upon a guaiac-based test will result in missed opportunities for investigation owing to its poor sensitivity. Despite its appealing convenience and generally accurate positive results, it should not be part of the routine evaluation for UGI bleeding.
February 29, 2020
TommyThe guaiac test is looking for the presence of peroxidase,
Peroxidase is found in many elements besides blood, making the test almost or completely useless in the clinical setting.
April 4, 2021
Kevin Bower, MD FACEPAlong these same lines of thinking, a normal H/H in an acute GI bleed would be thought of as unnecessary, and a low H/H could lead to an emergent endoscopy. The FOBT is only one piece of a puzzle that ER doctors use to decide if the patient has an acute medical condition. The value of a single FOBT has to be taken in context, and not as an absolute test that will determine further investigation.
June 15, 2023
Joseph WoodI appreciate Dr. Radecki’s thoughtful article. However, point-of-care testing looking for small amounts of occult GI blood are not really on point in emergency practice. EPs occasionally are asked to evaluate a chief complaint of black stools. As there are multiple causes of black stools, a point of care test that can reliably identify, or rule out, blood as the cause of the black stool is helpful and may help avoid some further testing. The real question then, is what’s the sensitivity and specificity of point-of-care testing of black stools for blood.