We appreciate the comments of Dr Schoen regarding our article.1 He is indeed correct that we have not reported the absolute prevalence of isolated advanced proximal neoplasia among persons undergoing colon cancer screening, but rather the prevalence of advanced proximal neoplasia among persons who had no adenomatous lesion on flexible sigmoidoscopy. In essence, what we have reported is the false-negative rate of flexible sigmoidoscopy. What Dr Schoen has reported is the absolute prevalence of isolated advanced proximal neoplasia that would be missed among the total population of persons undergoing screening with flexible sigmoidoscopy. We believe that these 2 values are complementary, even prior to the performance of sigmoidoscopy. The absolute miss rate allows patients and physicians to estimate the likelihood that an advanced lesion in the proximal colon will be missed, while the false-negative rate provides the posttest probability that a lesion remains, given a negative screening result. Knowledge of the false-negative rate can help people anticipate their level of comfort with a negative sigmoidoscopy result. These data can also be used to make decisions on the use of fecal occult blood testing in conjunction with screening sigmoidoscopy. We are grateful that Dr Schoen has highlighted the difference between these results and hope that both of these values will be helpful to practitioners counseling their patients.
Lewis JD, Ng K, Hung KE, et al. Prevalence of Isolated Advanced Proximal Neoplasia—Reply. Arch Intern Med. 2003;163(17):2103–2104. doi:10.1001/archinte.163.17.2103-a
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