Fecal DNA testing has shown greater sensitivity than guaiac-based occult blood tests for noninvasive colorectal cancer screening.
A prototype assay analyzed 22 gene mutations and a DNA integrity assay.
The prototype assay showed a sensitivity of 52% for colorectal cancer detection, and a specificity of 94% in average-risk individuals.
Dr Steven Itzkowitz and colleagues from New York determined the sensitivity and specificity of a second-generation assay.
The second assay uses improved DNA stabilization/isolation techniques, and a new promoter methylation marker.
|Vimentin methylation plus integrity assay had 88% sensitivity|
|Clinical Gastroenterology & Hepatology|
The investigative team reported that 40 patients with colorectal cancer, and 122 subjects with normal colonoscopy provided stool samples.
DNA preservation buffer was added immediately to these samples.
DNA was purified using gel-based capture.
The investigators analyzed the DNA for the original panel of 22 mutations, integrity assay, and 2 new promoter methylation markers.
The investigators used DNA that was optimally preserved and purified from stool.
The investigators found that the sensitivity of the prototype version 1 assay increased to 73% because of enhanced performance of integrity assay.
Vimentin gene methylation alone provided sensitivity and specificity of 73% and 87%, respectively.
The team noted that the optimal combination of vimentin methylation plus integrity assay resulted in 88% sensitivity and 82% specificity.
The investigators observed that cancers were detected regardless of stage or location.
False-positive vimentin methylation was associated with older age.
Dr Itzkowitz's team commented, “An improved fecal DNA test that incorporates only 2 markers shows much higher sensitivity for colorectal cancer.”
“The new assay is easier to perform and should be less costly, thereby facilitating its use for noninvasive colorectal cancer screening.”