Guaiac-based fecal occult blood tests for colorectal cancer screening are not specific for human hemoglobin and have low sensitivity.
Automated-development, immunochemical guaiac-based fecal occult blood tests are quality-controlled, and are specific for human haemoglobin.
The tests do not require diet restriction.
Dr Paul Rozen and colleagues from Israel measured the sensitivity and specificity of immunochemical fecal hemoglobin measurements in detecting cancer with colonoscopy.
The research team determined fecal hemoglobin thresholds that give the highest post-test probability for neoplasia.
The researchers also determined the number of immunochemical Guaiac-based fecal occult blood tests needed.
|The sensitivity of the test for cancer was 94%|
|Annals of Internal Medicine|
The researchers undertook a prospective, cross-sectional study in ambulatory endoscopy services.
The team evaluated 1000 consecutive ambulatory patients.
Some of the patients were asymptomatic but at increased risk for colorectal neoplasia.
The symptomatic patients underwent elective colonoscopy, and volunteered to prepare immunochemical guaiac-based fecal occult blood tests.
The hemoglobin content of 3 bowel movements was measured.
The team compared the highest value with colonoscopy findings.
Sensitivity, specificity, and predictive values were calculated.
The researchers measured likelihood ratios, and 95% confidence intervals of fecal hemoglobin measurements for clinically significant neoplasia.
The team assessed the relationship of these outcomes to the amount of fecal hemoglobin measured, and the number of immunochemical tests performed.
The researchers found that colonoscopy identified clinically significant neoplasia in 91 patients.
Colonoscopy identified cancer in 17 patients, and advanced adenomas in 74 patients.
Using 3 immunochemical guaiac-based fecal occult blood tests and a hemoglobin threshold of 75 ng/mL of buffer, sensitivity and specificity were 94% and 88%, respectively, for cancer.
The team found that the sensitivity and specificity for significant neoplasia was 67% and 91%, respectively.
The team reported that some patients were tested while discontinuing aspirin and anticoagulant therapies.
In addition, the team highlighted that study patients were at increased risk, and the results may not apply to average-risk populations.
Dr Rozen's team concludes, “Quantitative immunochemical guaiac-based fecal occult blood tests have good sensitivity and specificity for detection of clinically significant neoplasia.”
“Test performance in screening average-risk populations is not known.”