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Seema Qaiyumi, MD Georgetown University Hospital February 17, 2009

Comparative Evaluation of Immunochemical Fecal Occult Blood Tests for Colorectal Adenoma Detection A nnals of Internal Medicine : February 3, 2009 Seema Qaiyumi, MD Georgetown University Hospital February 17, 2009 Background Colorectal Cancer is the 3 rd most common cancer in the world.

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Seema Qaiyumi, MD Georgetown University Hospital February 17, 2009

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  1. Comparative Evaluation of Immunochemical Fecal Occult Blood Tests for Colorectal Adenoma DetectionAnnals of Internal Medicine : February 3, 2009 Seema Qaiyumi, MD Georgetown University Hospital February 17, 2009

  2. Background • Colorectal Cancer is the 3rd most common cancer in the world. • 1 million new cases and >500,000 deaths per year. • Most cases are sporadic and develop from removable precancerous lesions (adenomas) and curable early stage cancer. • Screening has a high potential for reducing morbidity and mortality. • RCT demonstrate reduced mortality with guaiac based Fecal Occult Blood Testing (FOBT) followed by sigmoid or colonoscopy if FOBT is positive.

  3. Fecal Occult Blood Testing • Guaiac based • Chemical reaction on a paper card which detects pseudoperoxidase activity of heme or hemoglobin • Limitations • Not specific for human hemoglobin • False +/- results from compounds in medications or food • (undercooked red meat, Vitamin C supplements) • Low diagnostic performance for precursors • Advantages • Low cost • Easy to do in physician’s office with adequate training for reading and interpretation

  4. Immunochemical FOBT • Use specific antibodies against human blood components to overcome diet/medication restrictions • Quantitative FOBTs • Qualitative FOBTs • Use immunochromatographic technology to allow simple office based analysis • Differences exist that may influence the diagnostic performance (especially in detection of precursor lesions) • Antibodies used • Different detection limits

  5. Study Aim Determine and compare performance characteristics of different qualitative immunochemical FOBTs for the detection of colorectal adenomas in a large sample of women and men undergoing screening colonoscopy

  6. Methods • Part of ongoing screening study including 20 GI practices in SW Germany from January 2006 -December 2007 • Patients Included: 1319 patients undergoing routine screening colonoscopy

  7. Methods • Patients excluded • Visible rectal bleeding or preceding + FOBT • Inflammatory Bowel Disease • Colonoscopy within 5 years • Stool samples collected after colonoscopy • Inadequate bowel prep • Incomplete colonoscopy • Histologically confirmed diagnosis of CRC • Non defined polyps (no histology reports available) • Pseudopolyps (likely UC/IBD) • President Bush

  8. Methods • Stool collection • Participants were given 1 test card for guaiac-based FOBT, a small 60mL container for stool collection, collection tissue and detailed instructions for stool collection • Samples were collected at home using specific instructions for collection and storage • Samples were brought on the day of colonoscopy and shipped on dry ice to a central lab for analysis

  9. Stool Tests • Done by PA’s who were blinded to colonoscopy and stool guaiac results • Six Immunochemical FOBT’s used • Bionexia FOB-plus (Gottingen, Germany) • PreventID CC (Bensheim, Germany) • ImmoCARE-C (Voerde, Germany) • FOB advanced (Ahrensburg, Germany) • QuickVue iFOB (San Diego, California) • Bionexia Hb/Hp Complex (Gottingen, Germany)

  10. Data Analysis • Two independent technicians interpreted all FOBT tests • Interoobserver reliability was very good (ĸ statistics) • Sensitivity and Specificity of each test to detect adenoma was calculated

  11. Results

  12. Sensitivity & Specificity

  13. Positive Predictive Values

  14. Variation • Based on duration of sample storage prior to testing, no general trend for sensitivity or specificity • Whether stool samples were frozen or not did not appear to cause relevant differences based on sensitivity analysis

  15. Discussion • Stool tests are an integral component of CRC screening • Useful in patients who are unwilling/unable or when health care resources are limited • Marked differences were found when comparing multiple qualitative immunochemical FOBTs • Promising results found for only 2 tests: • immoCARE-C (25% - 96.7%) • FOB advanced (27% - 92.9%) • Higher sensitivities found for distal, large and multiple adenomas

  16. Other Studies • Magstream 1000/Hem SP (Tokyo, Japan) compared to colonoscopy (n=21,805) • Quantitative immunochemical FOBT based on magnetic agglutination • Sensitivity 22.3% - Specificity 95.5% • FlexSure OBT (Palo Alto, CA) compared to sigmoidoscopy (n=584) • Limited to distal lesions only • Sensitivity 29.5% - Specificity 97.3% • Studies comparing multiple immunochemical FOBT’s in parallel are few and have small numbers

  17. Study Strengths • Multiple immunochemical FOBTs compared in parallel • All participants had colonoscopies, regardless of FOBT outcome • FOB testers and colonoscopy MD’s were blinded to test results • Assessed test performance characteristics in the target population for screening (age and risk profile) • Distribution of findings (% of adenomas) was in accordance with other studies

  18. Study Limitations • Stool from only 1 day was collected • Underestimates sensitivity • Overestimates specificity • Stool was stored frozen instead of used fresh • Bias: Participants undergoing screening colonoscopy may be more health conscious than the general population • Limited by the accuracy of screening colonoscopy to detect precancerous lesions

  19. Summary • Qualitative immunochemical FOBT could be an option for future CRC screening • Careful evaluation of each test is needed given the differences among tests • Only 2 of the tests showed specificity needed to become part of routine testing of average risk populations

  20. References • Hundt, Sabrina MSc; Haug, Ulrike PhD; Brenner, Hermann MD, MPH. Comparative Evaluation of Immunochemical Fecal Occult Blood Tests; Annals of Internal Medicine. February 3, 2009. • Allison JE, Sakoda LC, Levin TR, Tucker JP, Tekawa IS, Cuff T, et al. Screening for colorectal neoplasms with new fecal occult blood tests: update on performance characteristics. Journal of the National Cancer Institute. 2007. 99:1462-70. • Morikawa T, Kato J, yamaji Y, Wada R, Mitsushima, T, Shiratori Y. A comparison of the immunochemical fecal occult blood test and total colonoscopy in the assympomatic population. Gastroenterology. 2005. 129: 422-8. • Ferlay J, Bray F, Pisani, P, Parkin DM. GLOBOCAN 2002: Cancer Incidence, Mortality and Prevalence worldwide. IARC Cancer Base No 5. Version 2.0. Lyon France. IARC Pr 2004. • Arnold CN, Goel A, Blurm HE, Boland CR. Molecular pathogenesis of colorectal cancer; implications for molecular diagnosis. Cancer. 2005. 104: 2035-47. • Hewitson P, Glasziou P, Irwig L, Towler B, Watson E. Screening for colorectal cancer using the fecal occult blood test, Hemoccult. Cochrane Database. Systematic review 2007: CD001216. • Jaffe RM, Kasten B, Young DS, MacLowry JD. False-negative stool occult blood tests caused by ingestion of ascorbic acid (Vitamin C). Annals of Internal Medicine. 1975; 83: 824-26.

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