CAP TODAY Pathology/Laboratory Medicine/Laboratory Management
Fecal hemoglobin concentration and severity of colorectal neoplasia
Guaiac fecal occult blood tests are used to screen patients for colorectal neoplasia. However, fecal immunochemical tests (FIT) are beginning to replace this test because they are more specific for human fecal hemoglobin concentration (f-Hb). Using a quantitative FIT, the f-Hb concentration may be used as a cutoff to select those who should undergo additional investigative measures, such as colonoscopy. A commentary published with this study suggested that there may be a continuum of increasing risk for colorectal neoplasia as the f-Hb increases from zero. The authors examined this hypothesis via an observational study assessing colonoscopy and pathology findings in patients who were above the f-Hb cutoff for FIT. This will help to determine the test’s usefulness for first-line screening. The authors examined f-Hb from 38,720 subjects who ranged in age from 50 to 75 years. Additional colonoscopy findings and pathology data were collected on the 943 subjects with an f-Hb of 400 ng Hb/mL or greater. Of the 814 participants with outcome data available, 39 had cancer, 190 high-risk adenoma, and 119 low-risk adenoma. Median f-Hb concentration was higher in those subjects with cancer compared to those with no neoplasia or those with low-risk adenoma. Of interest, 74.4 percent of the subjects with cancer had an f-Hb greater than 1,000 ng Hb/mL compared with 58.4 percent with high-risk adenoma and 44.1 percent with no pathology. The authors concluded that f-Hb is related to severity of colorectal neoplastic disease in an average-risk population. Therefore, this study has implications for selecting the appropriate cut-off concentration for bowel cancer screening programs. However, the authors noted that a limitation of the study was that f-Hb could not be fully assessed since the upper analytical limit was 1,000 ng Hb/mL. This must be taken into consideration as subjects with large cancers may have had f-Hb far higher than 1,000 ng Hb/mL.
Digby J, Fraser CG, Carey FA, et al. Faecal haemoglobin concentration is related to severity of colorectal neoplasia. J Clin Pathol. 2013;66:415–419.
Correspondence: Jayne Digby at jaynedigby@nhs.net