title: Comparison of a guaiac and an immunochemical faecal occult blood test for the detection of colonic lesions according to lesion type and location.
abstract: We investigated variations in sensitivity of an immunochemical (I-FOBT) and a guaiac (G-FOBT) faecal occult blood test according to type and location of lesions in an average-risk 50- to 74-year-old population. Screening for colorectal cancer by both non-rehydrated Haemoccult II G-FOBT and Magstream I-FOBT was proposed to a sample of 20 322 subjects. Of the 1615 subjects with at least one positive test, colonoscopy results were available for 1277. A total of 43 invasive cancers and 270 high-risk adenomas were detected. The gain in sensitivity associated with the I-FOBT was calculated using the ratio of sensitivities (RSN) according to type and location of lesions, and amount of bleeding. The gain in sensitivity by using I-FOBT increased from invasive cancers (RSN=1.48 (1.16-4.59)) to high-risk adenomas (RSN=3.32 (2.70-4.07)), and was inversely related to the amount of bleeding. Among cancers, the gain in sensitivity was confined to rectal cancer (RSN=2.09 (1.36-3.20)) and concerned good prognosis cancers, because they involve less bleeding. Among high-risk adenomas, the gain in sensitivity was similar whatever the location. This study suggests that the gain in sensitivity by using an I-FOBT instead of a G-FOBT greatly depends on the location of lesions and the amount of bleeding. Concerning cancer, the gain seems to be confined to rectal cancer.
authors.affiliation: Cancers and Populations, ERI3 INSERM, UFR de Médecine, CHU de Caen, Caen, France. guittet-l@chu-caen.fr
authors.forename: L
authors.initials: L
authors.lastname: Guittet
authors.forename: V
authors.initials: V
authors.lastname: Bouvier
authors.forename: N
authors.initials: N
authors.lastname: Mariotte
authors.forename: J P
authors.initials: JP
authors.lastname: Vallee
authors.forename: R
authors.initials: R
authors.lastname: Levillain
authors.forename: J
authors.initials: J
authors.lastname: Tichet
authors.forename: G
authors.initials: G
authors.lastname: Launoy