Failure of rectal ornithine decarboxylase to identify adenomatous polyp status

Rectal mucosal ornithine decarboxylase (ODC) activity has been reported to distinguish between patients with and without adenomatous polyps (AP). In the present investigation, ODC activity has been measured in 28 patients with AP and 34 patients without AP. To assess the intraindividual variation in ODC activity, repeat biopsies were performed on 11 patients. In addition, the effect of postbiopsy sample handling was investigated by storage of samples on either dry or wet ice during transport to the laboratory. The mean rectal mucosal ODC activity in patients with AP was 196.0 +/- 195.5, whereas that in AP negative patients was 182.2 +/- 320.5. The rectal mucosal ODC activity in patients with colorectal cancer was 388.2 +/- 581. Repeat samples in individuals were generally within the same range as the original samples. The method of sample transport did not significantly affect the level of ODC measured in a particular biopsy. Because of high variability in rectal mucosal ODC activity within the population, there was wide overlap in ODC values between those patients with and without AP in an unselected general population. Thus, the measurement of flat rectal mucosal ODC activity is not a good predictor of the presence or absence of AP. Additional studies of the factors affecting mucosal ODC activity are necessary before the potential clinical utility of the method can be realized in the general population.