NEW YORK (Reuters Health) – A quantitative immunochemical fecal occult blood test (FOBT) is superior to the standard guaiac-based FOBT for detecting advanced colorectal neoplasms and cancer, say researchers from Korea.
Use of the immunochemical FOBT seems to be gaining momentum. Previous research has shown superior results with the immunochemical FOBT for colorectal cancer screening (see Reuters Health story of Aug 4, 2008). Research also shows greater participation in colorectal cancer screening when the immunochemical FOBT is used (see Reuters Health story of Dec 30, 2009).
For a study reported online May 25th in the American Journal of Gastroenterology, Dr. Dong Il Park from Sungkyunkwan University School of Medicine in Seoul and colleagues compared the standard guaiac-based test with a laboratory-based, automated, quantitative immunochemical FOBT (qFIT) for the detection of advanced colorectal neoplasia or colorectal cancer in 770 average-risk individuals undergoing screening colonoscopy.
Adenomas were present in 278 individuals (28.4%), advanced adenomas in 59 (7.7%), and invasive cancer in 13 (1.7%).
The guaiac-based test was positive in 61 (7.9%) of individuals. The qFIT was positive in 94 (12.2%) at a threshold of 75 ng/mL and in 86 (11.2%) at a threshold of 100 ng/mL.
The positive rates of the guaiac-based test did not differ between patients with adenomas and patients with normal colonoscopy results, whereas the positive rates of the qFIT at either threshold were significantly higher in patients with adenomas.
At all hemoglobin thresholds, the qFIT was more sensitive than the guaiac-based test for cancer or advanced colorectal neoplasia, but the specificities were comparable for the 2 tests.
For the guaiac-based test, the positive predictive values were 13.1% for advanced adenomas, 19.7% for advanced colorectal neoplasia, and 6.7% for colorectal cancer. The positive predictive values with qFIT (using the 100 ng/mL cut point and 3-sample qFIT results) were 23.3%, 36.0%, and 12.8%, respectively.
Negative predictive values for advanced adenomas, advanced colorectal neoplasia, and colorectal cancer were high, with considerably overlapping confidence intervals for the 2 tests.
The number of colonoscopies needed to detect cancer or advanced neoplasia after a positive test was lower with the qFIT (6.5 to 9.1 for cancer and 2.7 to 2.9 for advanced colorectal neoplasia, depending on the threshold chosen) than with the guaiac-based test (15.2 for cancer and 5.1 for advanced colorectal neoplasia).
“The qFIT provides a higher sensitivity for detecting advanced colorectal neoplasia and cancer than the guaiac-based test with an acceptable specificity, and can significantly reduce the number of colonoscopies needed in an average-risk Korean population,” the researchers conclude.
“In addition,” they say, “the qFIT provides the ability to choose a level of sensitivity and specificity appropriate for the patient’s clinical characteristics.”
Reference:
http://www.nature.com/ajg/journal/vaop/ncurrent/abs/ajg2010179a.html
Am J Gastroenterol 2010.
