A Pan-detecting Assay Based on Stool Samples for Taiwanese Population

Background and objective: Fecal occult blood test (FOBT) is a convenient tool for the screening of asymptomatic gastrointestinal (GI) bleeding while 「guaiac-based fecal occult test (G-FOBT) 」 is increasingly replaced by the use of an 「immunochemical-based test (I-FOBT) 」 that reacts with human globin, a protein that is digested by upper GI enzymes and is specific for detecting lower GI bleeding. However, in Taiwan, although the incidence of colorectal cancer is rapidly increasing, Helicobacter pylori-related upper GI pathologies remain highly prevalent, which may imply that mass screening solely based on I-FOBT could be insufficient as significant upper GI pathologies can be missed. Since I-FOBT dose not predict upper GI pathologies, the adjuncts of G-FOBT and H. pylori stool-antigen test (HpSA) may be a potential candidate to realize a pan-detecting assay based on stool samples in a population in which both lower and upper GI lesions are equally prevalent.

Patients: Our study will enroll consecutive subjects participating in the health check-up at National Taiwan University Hospital (Health Management Center), who will undergo I-FOBT, G-FOBT, HpSA, colonoscopy and EGD. The diagnostic values of three fecal testing, alone or in combination, will be respectively evaluated. knowing that subjects who were detected with gastrointestinal tract cancers might be small based on one screening setting, we also recruited patients who were detected with gastrointestinal tract cancers at other screening sites and were referred to the National Taiwan University Hospital for confirmatory diagnosis and treatment. They were also requested to complete the three fecal tests as well as the bidirectional endoscopies; however, it should be noted that, in this group of patients, those who completed only one of the bidirectional endoscopies were still eligible.

Our primary hypothesis was to test whether a guaiac-based test combined with an immunochemical test could help differentiate occult bleeding in the upper gastrointestinal tract from that in the lower gastrointestinal tract. As such a hypothesis would not be held, we also evaluated an alternative choice based on Helicobacter pylori stool antigen test to catching the upper gastrointestinal tract lesions.