The guaiac fecal occult blood test is recommended as a screening test for colorectal cancer but its low sensitivity has prevented its use globally.
Dr Guy Launoy and colleagues from France compared the performances of the reference guaiac and the immunochemical fecal occult blood test.
The tests used different positivity cut-off values in an average risk population sample of 10,673 patients who completed the 2 tests.
|Immunochemical fecal occult blood test had a sensitivity of 90%|
Patients with at least 1 test positive were asked to undergo colonoscopy.
Using the cut-off point of 20 ng/ml hemoglobin, the gain in sensitivity with immunochemical fecal occult blood tests was balanced by a decrease in specificity.
The research team found that the number of extra false positive results associated with the detection of 1 extra advanced neoplasia was 2.2.
The team noted that using a threshold of 50 ng/ml, immunochemical fecal occult blood test detected twice as many advanced neoplasias.
With a threshold of 75 ng/ml, the use of immunochemical fecal occult blood test allowed a gain in sensitivity of 90%.
The researchers found that using the higher threshold, the immunochemical fecal occult blood test decreased false positive rates of 33% for advanced neoplasia.
Dr Launoy's team concludes, “Evidence in favour of the substitution of guaiac fecal occult blood test by immunochemical fecal occult blood test is increasing."
"This gain is more important for high risk adenomas than for cancers.”
“The automated reading technology allows choice of the positivity rate associated with an ideal balance between sensitivity and specificity.”