Report in English with a Dutch summary (KCE reports 45A)

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64 Screening for Colorectal Cancer KCE reports vol.45 Aside from the classical guaiac FOBT there has been the development of immunochemical FOBTs (iFOBT) specifically designed to detect human hemoglobin in dried fecal samples. They contain polyclonal anti-human hemoglobin antibodies that react with the globin portion of undegraded hemoglobin. Because they are specific for human blood in feces, no special dietary restrictions are required 270. Restrictions on intake of drugs that easily induce gastro-intestinal erosions and hemorrhage, however, remain. Hemoglobin from upper G.I. bleeding (i.e., oral cavity, oesophagus, stomach or small intestine) is generally degraded by bacterial and digestive enzymes before reaching the large intestine and is therefore rendered immunochemically nonreactive. Conversely, hemoglobin from lower G.I. bleeding (i.e., caecum, colon or rectum) undergoes less degradation and can therefore remain immunochemically reactive. Thus, immunochemical fecal occult blood tests which detect undegraded hemoglobin have, in theory, increased biological specificity for lower G.I. bleeding and any associated pathology 270, and therefore could lower the overall cost of detecting these disorders by lowering colonoscopy rates 196, 202-205. However, we have to keep in mind that all fecal occult blood tests are subject to certain limitations inherent to lesions that bleed intermittently with non-uniform distribution of blood in feces. There is much variation between iFOBT tests and they are more expensive. They are also less studied than the classic gFOBT test. Immunochemical FOBTs require sample collection from 2 stools (InSure OC- Hemodia), 3 stools (HemeSelect, FlexSure OBT, MonoHaem), or 1 stool (Instant-View, immoCARE) 270. For InSure the sample is collected by brushing the surface of the stool while in the toilet bowl water, avoiding the gFOBT requirement for dry specimen collection, which is easier to handle and thus claimed to be more patient friendly and thereby increase screening compliance 201. The test formats for several iFOBTs require minimal processing and involve developing a test strip with controls and reading a colour reaction. Some iFOBT formats require more extensive laboratory processing (HemeSelect, OC- Hemodia). In the case of the InSure, all tests are exclusively developed by a private laboratory company (U.S.). Magstream 1000 271, 196, 202 and Hem SP 272, 273 provide automatic instrumental test development and reading with adjustable sensitivity threshold. Advantages and disadvantages of iFOBT compared with gFOBT are summarized in Table 14.
KCE reports vol.45 Screening for Colorectal Cancer 65 Table 14: Advantages and disadvantages of iFOBT compared with gFOBT Advantages of fecal immunochemical test (iFOBT) compared with gFOBT Improved specificity Potential increase in patient compliance iFOBTs will not react with non-human hemoglobin, vitamins, drugs, or peroxidase from food sources. They also showed to be non-reactive with blood from the upper gastrointestinal tract provided bleeding is occult. Since no dietary restrictions are needed, iFOBT may be more acceptable to the consumer than current gFOBT tests. Disadvantages of an fecal immunochemical test (iFOBT) compared with gFOBT Limited clinical testing Same sensitivity limitations More expensive Regional resources Colonoscopy resources limited Colonoscopy resources readily available No prospective, controlled trials of iFOBT screening and colorectal cancer incidence or mortality outcomes have been reported. However, if iFOBTs perform at least as well as gFOBT, it is likely that iFOBTs used for CRC screening would have at least the same efficacy in decreasing colon cancer mortality as gFOBTs 270. While iFOBTs have advantages over gFOBTs, they are still tests for occult blood, which may leak intermittently and may occur from sources in the colon and rectum other than cancers or large adenomas. Data indicate that the problem for detection created by intermittent bleeding is less marked with immunochemical than with guaiac tests because higher test sensitivity is not accompanied by significant degradation of specificity, as is the cause with guaiac tests. In addition, because bleeding from adenomas occurs infrequently, the potential for CRC prevention through adenoma detection and removal is likely to be lower with this and all FOBT methods than with endoscopic and imaging screening modalities. However when used annually, as recommended, the program sensitivity of FOBT is very high. See Table 15 Table 15 lists available FOBT test kits in Belgium 274, leaving some choice depending on availability of regional colonoscopy resources. Table 15: Choice of FOBT depending on colonoscopy resources Recommended FOBT Guaiac test with high specificity Fecal Immunochemical test (FIT) Guaiac test with high sensitivity Trade name Belgian supplier Price per test round (VAT incl.) Hemoccult® II Laméris 2,06 Instant-View® Hemostick® Actim Fecal Blood® Hemoccult® Sensa® Obelis Ventec Lucron Bioproducts Laméris N.V. ± 7 2,14 The Instant View FOBT II test comes in a set of fecal collection tubes, pre-filled with extraction buffer, with sampling stick and corresponding one-step lateral flow chromatographic immunoassay test cassettes (Instant View FOBT II casette
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KCE reports vol.45A Colorectale Kan
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2 Screening for Colorectal Cancer K
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KCE reports 1. Effectiviteit en kos
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