1.   This difference between mean disease durations in the two groups was statistically significant.

2.   Groups were comparable for age, sex, disease duration, and disease extent.

3.   All pairs were matched for age, sex, disease duration, and disease extent.

4.   The two groups were comparable for age, sex, disease duration, and disease extent.

5.   A barium enema performed at seven years disease duration showed recurrent polyps.

6.   In this series, however, one patient developed cancer after seven years disease duration so perhaps the criteria for entry should be widened.