Screening for Colorectal Cancer: The Accuracy of Fecal Occult Blood
- Graeme P. Young, MD, FRACP;
- D. James B. St. John, MBBS, FRCP, FRACP
Since this article does not have an abstract, we have provided the first 150 words of the full text.
Excerpt
To the Editor. —The recent article by Ahlquist et al1 concludes that fecal occult blood tests (FOBTs) have little value in early detection of colorectal cancer. This sweeping claim seems unjustified for two reasons.
The first is that FOBTs do not all test for the same analyte in stool specimens. Hemoglobin is degraded in feces to a range of different products, including free heme and heme-derived porphyrins (HDPs). Heme-derived porphyrins lack the peroxidase activity of heme on which guaiac tests depend.
The HemoQuant test (Mayo Medical Laboratories, Rochester, Minn; and SmithKline Beecham, Van Nuys, Calif) measures heme (free or in hemoglobin, myoglobin, or certain cytochromes) and HDPs.2 To claim, as Ahlquist et al do, that HemoQuant measures fecal hemoglobin is incorrect, as heme and HDPs are measured regardless of source and even when the globin moiety has been digested/degraded in the gut. As shown in this study and
