Limited Clinical Utility of the Fecal Occult Blood Test for Evaluation of Gastrointestinal Bleed in Hospitalized Patients

Abstract

Purpose: Fecal occult blood test (FOBT) is widely used for colorectal cancer screening in an outpatient setting. There is little data on whether an inpatient FOBT will guide clinical management. This is a study evaluating the clinical effectiveness of an inpatient FOBT to predict significant endoscopic lesions in the setting of a gastrointestinal (GI) bleed. Methods: We reviewed laboratory and endoscopic reports from hospitalized patients with FOBT performed over one year at a single university-based medical center. Statistical analysis was performed using the Chi Square test and multivariate regression analysis to determine whether the use of inpatient FOBT can predict significant endoscopic lesions. Results: A total of 575 anemic patients were checked for a guaiac-based FOBT during admission. Patient characteristics included ages 19-94 years (mean 58), 327 men, and 248 women. A total of 167 GI consults were placed and 119 patients underwent 182 endoscopies (89 EGD, 63 colonoscopy, and 30 flexible sigmoidoscopy). Among 67 overt GI bleeding patients, 79% were found to have positive endoscopic findings predominantly with high risk stigmata. Of those with positive endoscopic findings, 60.5% were FOBT positive and 41.5% were FOBT negative, clinically non-significant between the two groups (p=0.52). Among 52 suspected occult GI bleeding patients, FOBT and iron deficiency anemia status were not significantly different in predicting a clinically significant endoscopic lesion. On multivariate regression analysis, the strongest predictor for an endoscopic lesion was the presence of a low hemoglobin (OR 1.67; 95% CI 1.08-2.56; p<0.05). On the other hand, a positive FOBT correlated with an 80% probability of less positive endoscopic lesions (OR 0.20; 95% CI 0.04-0.95; p<0.05). Regardless of the FOBT status, the presence of GI symptoms coupled with abnormal imaging has a high predictive value of 64% for clinically significant endoscopic lesions. Conclusion: In our study, there is limited utility of checking FOBT in the inpatient setting. It is potentially harmful in a clinically overt GI bleeding patient. Thus, inpatient FOBT should not be checked in an overt GI bleeding patient with the potential for false negatives which may delay endoscopic intervention. Limitations of checking an inpatient FOBT in a suspected occult GI bleeding patient stem from high rates of false positives due to lack of strict dietary and medication adherence. Nonetheless, gastrointestinal symptoms coupled with an abnormal imaging and severe anemia is the most important predictor of a clinically significant endoscopic finding. Future prospective and randomized controlled trials are needed to determine if there is any role for FOBT in an inpatient setting.