Table 1.
Characteristics of normal screening samples and their follow-up for conventional cytology, SurePath, and ThinPrep. Values are numbers (percentages) unless stated otherwise
| Characteristics | Conventional | SurePath | ThinPrep | P value |
|---|---|---|---|---|
| Normal screening samples | 3 028 865 | 1 303 817 | 1 591 792 | |
| Person years at risk | 13 796 018 | 4 835 917 | 5 201 188 | |
| Normal screening sample followed by subsequent screening* | 1 931 397 (63.8) | 445 726 (34.2) | 370 519 (23.3) | <0.001 |
| Median (interquartile range) normal screening samples per woman | 1 (1-2) | 1 (1-1) | 1 (1-1) | <0.001 |
| Invasive cervical cancers diagnosed after normal screening sample | 1042 | 231 | 328 | <0.001 |
| Screen detected† | 414 | 84 | 103 | <0.001 |
| Clinically detected‡ | 628 | 147 | 225 | <0.001 |
| Follow-up time: | <0.001 | |||
| 0-12 months | 208 668 (6.9) | 73 905 (5.7) | 95 563 (6.0) | |
| 12-24 months | 105 945 (3.5) | 191 027 (14.7) | 321 784 (20.2) | |
| 24-36 months | 129 165 (4.3) | 187 410 (14.4) | 311 295 (19.6) | |
| 36-48 months | 203 768 (6.7) | 189 063 (14.5) | 284 262 (17.9) | |
| 48-60 months | 920 825 (30.4) | 334 677 (25.7) | 339 590 (21.3) | |
| 60-72 months, | 1 460 494 (48.2) | 327 735 (25.1) | 239 298 (15.0) | |
| Age, years: | <0.001 | |||
| 29-33 | 411 873 (13.6) | 167 015 (12.8) | 193 998 (12.2) | |
| 34-38 | 503 889 (16.6) | 187 179 (14.4) | 217 213 (13.6) | |
| 39-43 | 516 728 (17.1) | 218 559 (16.8) | 267 194 (16.8) | |
| 44-48 | 482 822 (15.9) | 218 476 (16.8) | 267 585 (16.8) | |
| 49-53 | 434 620 (14.3) | 192 594 (14.8) | 240 801 (15.1) | |
| 54-58 | 381 312 (12.6) | 173 572 (13.3) | 219 277 (13.8) | |
| 59-63 | 297 621 (9.8) | 146 422 (11.2) | 185 724 (11.7) | |
| Screening history: | <0.001 | |||
| No history§ | 396 174 (13.1) | 167 880 (12.9) | 194 251 (12.2) | |
| 1 smear ≤7 years¶ | 446 673 (14.7) | 156 727 (12.0) | 183 294 (11.5) | |
| 1 smear >7 years** | 35 164 (1.2) | 15 388 (1.2) | 20 003 (1.3) | |
| ≥2 smears ≤7 years†† | 2 095 417 (69.2) | 941 575 (72.2) | 1 164 713 (73.2) | |
| ≥2 smears >7 years‡‡ | 55 437 (1.8) | 22 247 (1.7) | 29 531 (1.9) | |
| Socioeconomic status: | <0.001 | |||
| Low | 248 097 (8.2) | 153 494 (11.8) | 108 492 (6.8) | |
| Middle | 2 501 696 (82.6) | 1 038 602 (79.7) | 1 337 521 (84.0) | |
| High | 232 658 (7.7) | 87 193 (6.7) | 132 863 (8.3) | |
| Unknown | 46 414 (1.5) | 24 528 (1.9) | 12 916 (0.8) |
Clinically detected cancer=not detected through programme screening.
*These differences are mainly caused by differences in follow-up time (see also fig 2). Differences in length of follow-up were accounted for in all analyses. Sensitivity analyses were restricted to women with subsequent attendance at screening programme.
†Include all cancers detected in first screening round following normal screening sample of ThinPrep, SurePath, or conventional cytology. ‡Include all cancers detected outside screening programme following normal screening sample of ThinPrep, SurePath, or conventional cytology.
§No history of cytological smears (inside or outside screening programme) before normal screening sample.
¶History of one cytological smear taken <7 years before normal screening sample.
**History of one cytological smear taken >7 years before normal screening sample.
††History of ≥2 cytological smears, last taken <7 years before normal screening sample.
‡‡History of ≥2 cytological smears, last taken >7 years before normal screening sample.