Robert H. Fletcher, MD, MSc
Does the immunochemical fecal occult blood test (iFOBT) accurately detect lesions in the lower gastrointestinal (GI) tract?
Blinded comparison of the iFOBT with endoscopists' diagnosis after bidirectional endoscopies.
Far Eastern Memorial Hospital in Taiwan.
2796 adults ≥ 18 years of age (mean age 49 y, 59% men) who had bidirectional endoscopies as part of a self-paid medical check-up. Exclusion criteria included overt GI symptoms or bleeding, and history of malignancy, colon polyps, inflammatory bowel disease, or bowel surgery.
The iFOBT is a 1-step commercial test with a brush-type sampler (OC-Light, Eiken Chemical Co. Ltd., Tokyo, Japan). Patients were to collect stool samples ≤ 2 days before beginning bowel preparation for the endoscopies. Samples were sent by the hospital to the laboratory for immediate testing. The positive cutpoint was 50 ng/mL.
Endoscopies were performed with a standard colonoscope (CF-H260AZI, Olympus, Tokyo, Japan) and esophagogastroduodenoscope (GIF-H260Z, Olympus) by 2 endoscopists who had each performed ≥ 3000 colonoscopies. Lesions identified as important during endoscopy were confirmed clinically.
Sensitivity, specificity, and likelihood ratios for positive and negative results for important lesions. Important lower GI lesions were colorectal cancer, colonic adenoma, carcinoid, colitis or ulcer, angiodysplasia, and submucosal tumor. Important upper GI lesions included cancer, esophageal varix, ulcer ≥ 0.5 cm in diameter with perceptible depth, angiodysplasia, submucosal tumor, and reflux esophagitis with severity ≥ Los Angeles class C or D.
14% of patients had a positive iFOBT result, 24% had important lower GI lesions, and 18% had important upper GI lesions. A positive iFOBT result detected no more lesions in the upper GI tract than a negative iFOBT result (21% vs 18%, P = 0.12). Diagnostic characteristics of the iFOBT for detecting important lower GI lesions are in the Table.
The immunochemical fecal occult blood test had high sensitivity and moderate specificity for detecting colorectal cancer but low sensitivity and moderate specificity for detecting other important lower gastrointestinal lesions. It was not useful for detecting important upper gastrointestinal lesions.
*Diagnostic terms and CI defined in Glossary. Gold standard = clinical confirmation of lesions identified during endoscopies.
†Colorectal cancer, colonic adenoma, carcinoid, colitis or ulcer, angiodysplasia, and submucosal tumor.
Fletcher RH. Immunochemical FOBT was accurate for detecting colorectal cancer but less so for other GI lesions. Ann Intern Med. ;156:JC2–10. doi: 10.7326/0003-4819-156-4-201202210-02010
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Published: Ann Intern Med. 2012;156(4):JC2-10.
Cancer Screening/Prevention, Colorectal Cancer, Gastroenterology/Hepatology, Gastrointestinal Cancer, Hematology/Oncology.
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Print ISSN: 0003-4819 | Online ISSN: 1539-3704
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