Table 1.
Characteristics of the Model Development, Internal Validation, and External Validation Cohorts
| Characteristics | Model development cohort 2014–2019 | Internal validation cohort 2014–2019 | P value | External validation cohort 2020–2022 | P value |
|---|---|---|---|---|---|
| Cohort members, n | 36,994 | 15,854 | 38,242 | ||
| Patient demographic and clinical characteristics at surveillance | |||||
| Age, y | |||||
| Mean (SD) | 66 (8) | 66 (8) | .96 | 67 (8) | <.001 |
| Sex, n (%) | .29 | .29 | |||
| Female | 15,403 (41.6) | 6522 (41.1) | 15,776 (41.3) | ||
| Male | 21,591 (58.4) | 9332 (58.9) | 22,466 (58.7) | ||
| Race and ethnicity, n (%) | .79 | <.001 | |||
| Asian or Pacific Islander | 6079 (16.4) | 2570 (16.2) | 6973 (18.2) | ||
| Black | 2104 (5.7) | 875 (5.5) | 2299 (6.0) | ||
| Hispanic | 3832 (10.4) | 1673 (10.6) | 4199 (11.0) | ||
| White | 18,785 (50.8) | 8106 (51.1) | 15,437 (40.4) | ||
| Other and missing | 6194 (16.7) | 2630 (16.6) | 9334 (24.4) | ||
| First-degree family history of colorectal cancer, n (%) | .13 | .55 | |||
| Yes | 6777 (18.3) | 2816 (17.8) | 6941 (18.2) | ||
| No (default) | 30,217 (81.7) | 13,038 (82.2) | 31,301 (81.8) | ||
| Body mass index (kg/m2) | |||||
| Mean (SD) | 29 (6) | 29 (6) | .94 | 28 (6) | <.001 |
| Median (IQR) | 28 (25–32) | 28 (25–32) | .98 | 27 (24–31) | <.001 |
| Ever smoked tobacco, n (%) | .70 | <.001 | |||
| Yes | 13,220 (35.7) | 5693 (35.9) | 11,520 (30.1) | ||
| No (default) | 23,774 (64.3) | 10,161 (64.1) | 26,722 (69.9) | ||
| Diabetes | .35 | <.001 | |||
| Yes | 7444 (20.1) | 3247 (20.5) | 8306 (21.7) | ||
| No | 29,550 (79.9) | 12,607 (79.5) | 29,936 (78.3) | ||
| Index colonoscopy-related characteristics | |||||
| Performed within KPNC (and have information), n (%) | .81 | <.001 | |||
| Yes | 34,422 (93.0) | 14,761 (93.1) | 37,275 (97.5) | ||
| No | 2572 (7.0) | 1093 (6.9) | 967 (2.5) | ||
| Extent of examination, n (%) | <.05 | <.001 | |||
| Complete to cecum | 33,324 (90.1) | 14,311 (90.3) | 36,574 (95.6) | ||
| Incomplete | 181 (0.5) | 53 (0.3) | 158 (0.4) | ||
| Missing | 3489 (9.4) | 1490 (9.4) | 1510 (3.9) | ||
| Bowel preparation, n (%) | .64 | <.001 | |||
| Good or excellent | 27,937 (75.5) | 12,018 (75.8) | 33,367 (87.3) | ||
| Poor or fair | 3982 (10.8) | 1710 (10.8) | 2898 (7.6) | ||
| Missing | 5075 (13.7) | 2126 (13.4) | 1977 (5.2) | ||
| Colonoscopy indication, n (%) | .96 | <.001 | |||
| Screening | 10,292 (27.8) | 4362 (27.5) | 9772 (25.6) | ||
| Diagnostic | 8336 (22.5) | 3593 (22.7) | 7484 (19.6) | ||
| Positive fecal test | 6987 (18.9) | 3008 (19.0) | 7615 (19.9) | ||
| Surveillance | 8807 (23.8) | 3798 (24.0) | 12,404 (32.4) | ||
| Missing | 2572 (7.0) | 1093 (6.9) | 967 (2.5) | ||
| ADR, all indications, % | .70 | ||||
| Median (IQR) | 36 (31–43) | 36 (31–43) | .19 | 46 (39–53) | <.001 |
| Missing, n (%) | 4795 (13.0) | 2055 (13.0) | 2933 (9.8) | ||
| Cutoff 32.5% | .70 | <.001 | |||
| <32.5 or missing | 14,722 (39.8) | 6338 (40.0) | |||
| ≥32.5 | 22,272 (60.2) | 9516 (60.0) | |||
| Cutoff 37.5% | <.001 | ||||
| <37.5 or missing | 10,829 (28.3) | ||||
| ≥37.5 | 27,413 (71.7) | ||||
| Time from index to surveillance colonoscopy, y, n (%) | .91 | <.001 | |||
| 2 to <3 | 1044 (2.8) | 453 (2.9) | 1624 (4.2) | ||
| 3 to <5 | 9281 (25.1) | 4009 (25.3) | 15,608 (40.8) | ||
| 5 to <7 | 18,642 (50.4) | 8022 (50.6) | 13,748 (36.0) | ||
| 7 to <10 | 4750 (12.8) | 1979 (12.5) | 4831 (12.6) | ||
| ≥10 | 705 (1.9) | 298 (1.9) | 1464 (3.8) | ||
| Missing | 2572 (7.0) | 1093 (6.9) | 967 (2.5) | ||
| Mean (SD) | 6 (2) | 6 (2) | .43 | 5 (2) | <.001 |
| Median (IQR) | 5 (5–6) | 5 (5–6) | .85 | 5 (4–6) | <.001 |
| Index colonoscopy findings | |||||
| Any adenoma, n (%) | .83 | <.001 | |||
| Yes | 25,296 (68.4) | 10,884 (68.6) | 29,176 (76.3) | ||
| No | 9126 (24.7) | 3877 (24.5) | 8099 (21.2) | ||
| Missing | 2572 (7.0) | 1093 (6.9) | 967 (2.5) | ||
| Adenoma with advanced histology, n (%) | .73 | <.001 | |||
| Yes | 2833 (7.7) | 1185 (7.5) | 2592 (6.8) | ||
| No | 31,598 (85.4) | 13,576 (85.6) | 34,683 (90.7) | ||
| Missing | 2572 (7.0) | 1093 (6.9) | 967 (2.5) | ||
| Polyp size ≥10 mm, n (%) | .22 | <.01 | |||
| Yes | 4146 (11.2) | 1697 (10.7) | 4061 (10.6) | ||
| No | 30,276 (81.8) | 13,064 (82.4) | 33,214 (86.9) | ||
| Missing | 2572 (7.0) | 1093 (6.9) | 967 (2.5) | ||
| 3 or more adenomas, n (%) | .77 | <.001 | |||
| Yes | 2958 (8.0) | 1296 (8.2) | 10,953 (28.6) | ||
| No | 31,464 (85.1) | 13,465 (84.9) | 26,322 (68.8) | ||
| Missing | 2572 (7.0) | 1093 (6.9) | 967 (2.5) | ||
| Worst finding, n (%) | .38 | <.001 | |||
| Advanced adenoma (size ≥10 mm or advanced histology) | 5696 (15.4) | 2364 (14.9) | 5693 (14.9) | ||
| Nonadvanced adenoma | 19,618 (53.0) | 8525 (53.8) | 23,493 (61.4) | ||
| No adenoma | 9108 (24.6) | 3872 (24.4) | 8089 (21.2) | ||
| Missing | 2572 (7.0) | 1093 (6.9) | 967 (2.5) | ||
| Risk status based on postpolypectomy surveillance guidelines, n (%) | .50 | <.001 | |||
| High risk | 7608 (20.6) | 3193 (20.1) | 13,879 (36.3) | ||
| Low risk | 26,814 (72.5) | 11,568 (73.0) | 23,396 (61.2) | ||
| Missing | 2572 (7.0) | 1093 (6.9) | 967 (2.5) |
P values for the medians are italicized.
Characteristics for the internal and external validation cohorts were compared to those for the development cohort. Chi-square tests, 2-sample t-tests, and Wilcoxon rank-sum tests were used to compare proportions, mean, and median values, respectively.
ADR, adenoma detection rate; IQR, interquartile range; KPNC, Kaiser Permanente Northern California; SD, standard deviation.