By Jeanette M. Daly, RN, PhD Department of Family Medicine, University of Iowa Fecal Occult Blood Unrecognized by the patient, bleeding is hidden Normal blood loss in a person is 0.5 to 1.5 ml/day Special tests detect fecal occult blood Guaiac Immunochemical Currently Food & Drug Administration approved 108 tests Technologies for Fecal Occult Blood Tests Guaiac tests 1901 Ismar Boas, German gastroenterologist, established guaiac test method Immunochemical tests 1978 George Barrows and colleagues developed fecal immunochemical tests (FIT) Fecal DNA Test 1992 David Sidransky detected colorectal cancer by DNA Extracts human DNA from the stool and tests it for alterations that have been associated with cancer Costs of Fecal Occult Blood Tests Guaiac-based tests $5-$10 CMS reimbursement is $5.54 Immunochemical tests $20-$25 CMS reimbursement is $23.22 Stool DNA tests $400-$800 CMS does not reimburse Guaiac-based Tests Detects heme in the stool on guaiac paper Heme component in hemoglobin has a peroxidase-like effect rapidly breaking down hydrogen peroxide that is dropped on the paper Feces is applied to the paper with an applicator One or two drops of hydrogen peroxide are dripped on the other side of the paper and it is observed for a rapid blue color change for a positive result Avoid red meat, certain vegetables and fruits, and nonsteroidal anti-inflammatory drugs and iron supplements (false positives) Avoid Vitamin C (false negatives) CLIA-waived Fecal Immunochemical Tests Newer test that detects occult blood in the stool Uses specific antibodies to detect human globin Manual type (for lower volume use) CLIA-waived and can be used in primary care setting Result read as negative/positive Are dry-slide Or liquid-based stored in stabilizing buffer Fecal Immunochemical Tests Automated type (for higher volume use) Not CLIA-waived Can run 80 samples/hour Machine costs ~ $30,000 Automated types OC-Auto Micro 90 or OC-Sensor Diana Can set cut-off values to read ng/ml, i.e., 100ng/ml of hemoglobin Can read as negative/positive Fecal Immunochemical Tests (FIT) Positivity cut-offs (ng Hb/ml) differ by manufacturer Stability of stool specimen different by manufacturer Product Type Detection Level Stability of Sample Beckman Coulter Hemoccult ICT Dry-slide, manual 200 ng Hb 14 days Quidel QuickVue Liquid-based, manual 50 ng Hb/ml 8 days Polymedco OCAuto Micro 80 Liquid-based, automated 100 ng Hg/ml 15 days Stability of Stool Specimen Heme or hemoglobin is not stable in stools Hemoglobin degradation due to bacterial activity related to the temperature Delay in testing stool sample results in greater decline of hemoglobin in positive samples Prolonged delays result in more false-negative tests Using liquid-based vial storage, mean daily hemoglobin decrease was 29ng Hg/ml1 Dry slide guaiac cards (Hemoccult II Sensa) results are stable for at least 19 days2 FIT Advantages Highly specific for occult lower GI bleeding Globin is degraded by upper GI enzymes and thus FIT does not detect blood from upper GI bleeding No dietary or drug restrictions for stool collection Can collect stool with no wait time FIT has higher sensitivity (100%) and specificity (86%) for colorectal cancer than guaiac sensitivity (62%) and specificity (96%) using 3 stool samples3 Achieving Best FIT Results FIT and FOBT may not detect a polyp or tumor that is not bleeding Multiple samples should be tested with FIT Although FIT is more sensitive to blood, the test is subject to the same sampling issues that affect clinical effectiveness of guaiac test Negative results may mean polyps are not bleeding Greater the number of stool samples tested, the higher the sensitivity for cancer or advanced colorectal neoplasia4,5,6 2-day tests are recommended FIT Patient Mailers Cost for mailing a liquid-based FIT is $1.90 Cost for mailing a dry-slide is $.45 Patient mailers for FIT are prepackaged Tips for Patients Collecting Stool Samples Wash your hands Urinate before defecating and then flush the toilet Avoid getting urine on the stool Lay rice paper on top of the water, having the stool avoid contact with the water Okay if the rice paper gets wet Collect from the stool that is not in water Use the probe or spatula to obtain stool Avoid overfilling the vial or card When Not to Collect Stool Sample Menstruating Three days prior to or after menstruation Bleeding hemorrhoids Blood visible in the toilet Bleeding cuts on your hand Toilet freshener in the toilet Rust or salt water in the toilet Directions for Reading Manual FITs Wear gloves and protective glasses Use timer Insert test strip in vials (Polymedco OC-Light) read at five minutes Pour drops from vial in cassette (Quidel QuickVue iFOB) and read in five minutes Important Fecal Occult Blood Test Points FIT is not suitable for detecting gastric (upper GI) bleeding For suspected gastric bleeding, use the traditional guaiac test Avoid digital rectal exam to obtain stool sample Trauma of exam could cause bleeding For guaiac - sensitivities for detecting advanced neoplasia in 284 patients was 4.9% for digital rectal exam and 23.9% for 6sample guaiac FOBT7 For FIT -positivite predictive value for CRC & large adenomatous polyps were 19.8% in DRE and 27.1% in routine screening.8 Mail stool sample same day as collection or next day Test stool sample day of receipt Conclusions FITs more sensitive for lower GI occult blood Hemoglobin in feces stored in liquid buffer degrades over time Two stool samples are recommended Those who have a positive FIT need follow-up with a colonoscopy References 1van Rossum LGM, van Rijn AF, van Oijen MGH, et al. False negative fecal occult blood tests due to delayed sample return in colorectal cancer screening. In. J. Cancer 2009;125:746-750. 2Young GP, Sinatra MA, St. John DJB. Influence of delay in stool sampling on fecal occult blood test sensitivity. Clinical Chemistry 1996;42:1107-1108. 3Levi Z, Birkenfeld S, Vilkin A, et al. A higher detection rate for colorectal cancer and advanced adenomatous polyp for screening with immunochemical fecal occult blood test than guaiac fecal occult blood test, despite lower compliance rate. A prospective, controlled, feasibility study. Int J Cancer 2011;128:2415-24. 4Yamamoto M, Nakama H. Cost-effectiveness analysis of immunochemical occult blood screening for colorectal cancer among three fecal sampling methods. Hepato-Gastroenterology 2000;47:396399. 5Levi Z, Rozen P, Hazazi R, et al. A quantitative immunochemical fecal occult blood test for colorectal neoplasia. Annals of Internal Medicine 2007;146:244-255. 6Park D, Ryu S, Kim YK, et al. Comparison of guaiac-based and quantitative immunochemical fecal occult blood testing in a population at average risk undergoing colorectal cancer screening. Am J Gastroenterol 2010;105:2017-2025. 7Collins JF, Lieberman DA, Durbin TE, et al. Accuracy of screening for fecal occult blood on a single stool sample obtained by digital rectal examination: A comparison with recommended sampling practice. Ann Intern Med 2005;142:81-85. 8Hakama H, Zhang B. Does stool collection method affect outcomes in immunochemical fecal occult blood testing? Dis Colon Rectum 2001;44:871-875.