Use of Fecal Immunochemical Tests

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
 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
Avoid red meat, certain vegetables and fruits, and nonsteroidal
anti-inflammatory drugs and iron supplements (false positives)
Avoid Vitamin C (false negatives)
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
 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
Stability of
Beckman Coulter
Hemoccult ICT
Dry-slide, manual
200 ng Hb
14 days
Quidel QuickVue
50 ng Hb/ml
8 days
Polymedco OCAuto Micro 80
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
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
 Pour drops from vial in cassette
(Quidel QuickVue iFOB) and
read in five minutes
Important Fecal Occult Blood Test
 FIT is not suitable for detecting gastric (upper GI) bleeding
 For suspected gastric bleeding, use the traditional guaiac
 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
 Mail stool sample same day as collection or next day
 Test stool sample day of receipt
 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
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test sensitivity. Clinical Chemistry 1996;42:1107-1108.
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.
M, Nakama H. Cost-effectiveness analysis of immunochemical occult blood screening
for colorectal cancer among three fecal sampling methods. Hepato-Gastroenterology 2000;47:396399.
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.
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.
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.
H, Zhang B. Does stool collection method affect outcomes in immunochemical fecal
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