How helpful is a new blood test for colorectal cancer? Elizabeth Tracey reports

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Blood tests for cancer are much in the news lately, including one to test for colorectal cancer. Such a test, if it works as well as methods like colonoscopy or fecal immunochemical testing, would allow people to give tedious aspects of these other methods a miss. Yet William Nelson, director of the Kimmel Cancer Center at Johns Hopkins, says we’re not there yet. 

Nelson: This is a test of circulating DNA in the blood and they're looking at DNA methylation changes that they see in colorectal cancer. They took 27,000 or more subjects who were going to undergo colonoscopy within 90 days, that was the gold standard. What did the test say, what a colonoscopy say that kind of comparison but they were able to exhibit the test had a sensitivity of 79% for cancer and a specificity of 92%, when they thought cancer was present, present 92% of the time. What ends up being challenging the so-called negative predictive value.      :32

At Johns Hopkins, I’m Elizabeth Tracey.