Table 3.

Timing of surveillance colonoscopy relative to recommended intervals according to guideline in effect (by period) and adenoma patient group, Kaplan-Meier analysis

Period of index colonoscopy	Recommended interval (year)	Too early (%)	Appropriate* (%)	Delayed or no surveillance (%)	No surveillance† (%)
June 1998–2001
1 adenoma (n=1676)	2–3	24	24	53	35
2 adenomas (n=397)	1	4	23	73	32
3+ adenomas (n=230)	1	6	30	63	22
Overall (n=2303)		19	24	57	33
In 2002
1 adenoma (n=417)	6	47	9	44	40
2 adenomas (n=160)	6	57	11	33	33
3+ adenomas (n=117)	3	39	18	43	33
Overall (n=694)		48	11	41	37
Overall, all patients (n=2997)		25	21	53	34

Due to rounding row percentages may not add up to 100%.

*Appropriate interval, before 2002: 1-year plus or minus 3 months, 2–3 years plus or minus 6 months; and in 2002: 3- or 6-years plus or minus 6 months.

†by the end of the study (1 December 2008) or within 90 months, whichever came first.