FEATURE
to issue a ruling that it was not a cov- ered service for screening, at least not at the present time.” CMS issued this ruling “because of the sensitivity and specificity data,” Johnson says. Sensitivity is the likeli- hood that a test will find cancers or adenomas if they exist; and specificity is the probability of a negative result in patients free from any lesions. “We grade polyp sizes in centime-
ters,” Johnson says. “A centimeter or greater is designated as a high-risk adenoma because there’s a higher risk that the polyp could have more pro- gressive risks for cancerous changes. Then we get into smaller polyps. We recognize, at least the recommenda- tions from all of the national gastro- enterology societies is, that polyps that are 6 mm or greater would need to be removed by a colonoscopy.
“The sensitivity data and specific- ity data from both the ACRIN and this present study are pretty much the same,” Johnson continues. “In the present An- nals of Internal Medicine study, they looked first at the larger polyps (>1 cm)— one centimeter or greater—and the sen- sitivity data was pretty close to what it had been for the ACRIN trial. The speci- ficity was 85 percent. In the ACRIN trial, the specificity was actually 86 percent. This latest trial had results a notch below what the ACRIN trial had.” Why is this important? “Let’s say
you’ve done a CTC and a radiologist finds a polyp,” Johnson says. “Then you come to me as a gastroenterologist and I say, ‘The colonoscopy showed that there was no polyp.’ Then you go back to the radiologist or primary care physi- cian and say the gastroenterologist said that there’s no polyp but you said there
was. Now there’s the potential for repeat testing as you try to determine a tie- breaker, which further increases health care expenses by duplicate testing. “Now you’ve already done two tests for a screening procedure, and that du- plicity of testing is a real concern for insurance payers, in particular CMS,” Johnson says. “If you take a specificity of 85 percent, in the case of the Annals of Internal Medicine study, you have a 15 percent false positive. That means that if you test every five years, which is what the index for screening would be by CTC, at the end of 10 years (dur- ing which three tests were performed at zero, five and 10 years), you would have sent nearly 45 percent of those patients for a colonoscopy, and that du- plicity of testing is what really killed the recommendation that this could be done for routine screening.”
ASC FOCUS MARCH 2013
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