1. Use of Fecal Immunochemical Tests
By Jeanette M. Daly, RN, PhD
Department of Family Medicine, University of Iowa

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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 OC-Auto Micro 80
Liquid-based, automated
100 ng Hg/ml
15 days

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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 6-sample 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

17. 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

18. 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:
2Young GP, Sinatra MA, St. John DJB. Influence of delay in stool sampling on fecal occult blood test sensitivity. Clinical Chemistry 1996;42:
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:
4Yamamoto M, Nakama H. Cost-effectiveness analysis of immunochemical occult blood screening for colorectal cancer among three fecal sampling methods. Hepato-Gastroenterology 2000;47:
5Levi Z, Rozen P, Hazazi R, et al. A quantitative immunochemical fecal occult blood test for colorectal neoplasia. Annals of Internal Medicine 2007;146:
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:
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: