Fecal Occult Blood Testing in Hospitalized and ED Patients

In This Article

Abstract and Introduction

Abstract

Objective: To examine the use of fecal occult blood testing in inpatients and in those presenting to the emergency department.

Methods: We retrieved all fecal occult blood tests (FOBTs) conducted over a 3 year period, gastrointestinal endoscopic studies, and diagnoses of digestive-tract malignant neoplasms. Scheduling reasons and procedure results for all gastrointestinal endoscopies scheduled within 30 days after the FOBT result became available were recorded.

Results: A total of 5028 FOBTs were obtained during the 3-year period. Half of the diagnostic endoscopic procedures (n = 957) completed within 30 days of FOBT followed a negative test result. The few reasons for scheduling endoscopic procedures included a positive FOBT result. During follow-up, 17 new diagnoses of digestive-tract malignant neoplasms were made, and 8 of 17 patients had 1 or more positive FOBT result.

Conclusions: The results of FOBTs, by themselves, are rarely used for patient management. Eliminating the routine diagnostic use of FOBTs in those settings would not compromise patient care.

Introduction

Although the usefulness of fecal occult blood tests (FOBTs) is occasionally questioned, they continue to be widely used in a number of settings, including as part of the physical examination during inpatient stay and at hospital admission.^[1,2] Although some guidelines^[3] support their use in colorectal carcinoma (CRC) screening, limited knowledge is available on their usefulness in areas other than CRC, such as investigation of gastrointestinal bleeds of additional etiologies (eg, after operations, iron deficiency anemia, peptic ulcer, and inflammatory bowel disease [IBD]).

FOBT assays are designed to detect hemoglobin molecules in fecal specimens as an indication of gastrointestinal (GI) bleeding that can be due to various pathologies, including GI inflammation^[1,4] and CRC.^[5] Guaiac-based FOBTs use the peroxidase-like activity of the heme molecule in hemoglobin, in the presence of hydrogen peroxide, to catalyze the oxidation of alpha-guaiaconic acid to a blue-colored quinone compound. An upper GI bleed is only detected by heme-based assays. Newer, more sensitive, and more specific antibody-based assays, such as fecal immunochemical testing (FIT), do not detect upper GI bleeds because the antigen (hemoglobin) will be digested and epitopes lost during GI passage.

The role of 3 sequential FOBTs in screening for CRC is well documented,^[6–9] and multisociety guidelines for early detection of CRC include their use.^[10] Two specimens are adequate for CRC screening with the newer, more sensitive FIT. However, there is little evidence for the appropriate use of single guaiac-based FOBTs among hospitalized patients.

In the era of evidence-based medicine, continued usage of guaiac-based FOBTs must be assessed in terms of outcomes. Ideally, test results should affect patient management. In the case of a positive FOBT result, standard texts recommend that a clinical assessment and a GI investigation, such as endoscopy, should follow. The selection of esophagogastroduodenoscopy (EGD) to examine the uppermost third of the GI tract vs colonoscopy to examine the lowermost third of the GI tract vs both procedures usually is dependent on other findings in the patient history and physical examination. This study examines patient management (endoscopic studies) after obtaining guaiac-based FOBTs during hospitalization or in the emergency department (ED).

Table 1. Reasons for and Findings on EGD Within 30 Days of FOBT Result
Variable	FOBT Negative Result (314 [51.6%])	FOBT Positive Result (294 [48.4%])	P Value^a
Reason for EGD^b
Iron-deficiency anemia, anemia, nausea, vomiting, diarrhea, abdominal pain, other^b	225 (71.7%)	120 (40.8%)	<.001
Occult bleeding^c	2 (.6%)	9 (3.1%)
Overt bleeding	87 (27.7%)	165 (56.1%)

EGD, esophagogastroduodenoscopy; FOBT, fecal occult blood testing.
^aPearson χ².
^bOther reasons for scheduling EGD were weight loss, possible cancer on imaging, gastrointestinal mass, unknown primary, previous cancer diagnosis, failure to thrive, genetic cancer risk, abdominal distension, screening for varices, dysphagia, odynophagia, gastroesophageal reflux disease (GERD), reflux, dyspepsia, possible inflammatory bowel disease (IBD), possible strongyloides, and/or peritonitis.

Table 2. Reasons for and Findings on Colonoscopy Within 30 Days of FOBT Result
Variable	FOBT Negative Result (177 [50.6%])	FOBT Positive Result (173 [49.4%])	P Value^a
Reason for Colonoscopy^b
Iron deficiency anemia, anemia, nausea, vomiting, diarrhea, abdominal pain, other^b	145 (81.9%)	81 (46.8%)	<.001
Occult bleeding^c	6 (3.4%)	19 (11.0%)
Overt bleeding	26 (14.7%)	73 (42.2%)

FOBT, fecal occult blood test.
^aPearson χ².
^bOther reasons for scheduling colonoscopy were weight loss, possible cancer on imaging, gastrointestinal mass, unknown primary, previous cancer diagnosis, failure to thrive, bowel obstruction, history of inflammatory bowel disease (IBD), infectious colitis, strongyloides, diverticulitis, possible inflammation on imaging.
^cA total of 17 patients (25 tests) with FOBT in the colonoscopy order; 4 patients had no other reason for having a colonoscopy ordered (1 patient with 2 positive test results and 1 negative test result, 1 patient with 3 positive test results, and 2 patients with 1 positive test result).