Diagnostic accuracy of immunochemical versus guaiac faecal occult blood tests for colorectal cancer screening.

Abstract

BACKGROUND:

Immunochemical tests show important advantages over chemical-based faecal occult blood tests (FOBT) for colorectal cancer (CRC) screening, but comparison studies are limited. This study was performed to compare the accuracy of a sensitive immunochemical test with the guaiac test for detecting significant neoplasia (advanced adenomas and CRC) in an average-risk population.

METHODS:

A random sample of 2288 asymptomatic subjects 50-79 years of age was prospectively included. Participants received three cards of the guaiac test, one sample of a latex-agglutination test (haemoglobin cut-off 50 ng/ml), and an invitation to undergo colonoscopy. Test sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were calculated in 1756 compliers.

RESULTS:

Immunochemical and guaiac tests were positive in 143 (8.1%) and 62 (3.5%) subjects, respectively. Complete colonoscopy, performed in 402 participants (158 FOBT+ and 244 FOBT-), detected 14 (0.8%) patients with CRC and 49 (2.8%) with advanced adenomas. The immunochemical and guaiac tests for significant colorectal neoplasia showed sensitivities of 61% versus 23.8%, specificities of 95.1% versus 97.7%, PPVs of 43.4% versus 39.0%, and NPVs of 97.5% versus 95.4%, respectively. Proximal significant neoplasms were more frequently detected with the immunochemical test (85% vs. 15%) The relative risk for detecting significant neoplasia was superior in patients with a positive immunochemical test (RR 16.93; CI 7.94-36.10) than with a positive guaiac test (RR 3.34; CI 2.17-5.15).

CONCLUSION:

A sensitive immunochemical test is markedly superior to the guaiac test for detecting significant colorectal neoplasia, and should be considered the first-choice FOBT for CRC screening in the average-risk population.

• Authors: Adolfo Parra-Blanco, Antonio Z Gimeno-García, Enrique Quintero, David Nicolás, Santiago G Moreno, Alejandro Jiménez, Manuel Hernández-Guerra, Marta Carrillo-Palau, Yoshinobu Eishi, Julio López-Bastida
• Journal: Journal of gastroenterology (J Gastroenterol) Vol. 45 Issue 7 Pg. 703-12 (Jul 2010) ISSN: 1435-5922 [Electronic] Japan
• PMID: 20157748 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Guaiac

Topics

• Aged
• Colonoscopy
• Colorectal Neoplasms (diagnosis)
• Female
• Guaiac
• Humans
• Immunologic Tests (methods)
• Male
• Mass Screening (methods)
• Middle Aged
• Occult Blood
• Predictive Value of Tests
• Prospective Studies
• Sensitivity and Specificity