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March 16, 2011

Performance of Immunochemical Fecal Occult Blood Tests Among Users of Low-Dose Aspirin—Reply

JAMA. 2011;305(11):1093-1094. doi:10.1001/jama.2011.298

In Reply: Our study does not assume that “neither chronic aspirin use nor underlying conditions associated with its use would alter the risk of CRC.” In fact, some of the key underlying conditions of low-dose aspirin use, higher age and male sex, are strongly related to CRC risk, and the key patterns observed in our study were even more pronounced after stratification of the study sample by such factors. Chronic aspirin use by itself is protective against colorectal neoplasms.1 In our study, prevalence of advanced colorectal neoplasms was exactly the same among users and nonusers (with slightly lower proportions of both invasive CRC and small advanced adenomas in the former), which most likely reflects a balance of divergent effects of aspirin use and factors associated with its use and does not support suggestions by Drs Chan and Schooling that differential stages explain the higher sensitivity of the tests for detection of colorectal neoplasms among low-dose aspirin users. In fact, the strong differences in sensitivity persisted when restricting the analysis to participants with large advanced neoplasms.