TABLE II.
Study population characteristics, stratified by the two different digital mammography vendor units.
| Vendor 1 | Vendor 2 | |
|---|---|---|
| Number of women | 1474 | 2804 |
| Age (mean ± SD) | 58.6 y ± 11.2 | 56.5 y ± 10.8 |
| Age at first menstrual period (mean ± SD) | 13.0 y ± 3.6 | 12.8 y ± 3.3 |
| Age at first child birth (mean ± SD) | 24.7 y ± 6.7 | 24.5 y ± 6.7 |
| BMI (mean ± SD) | 28.7 kg/mm2 ± 7.0 | 29.8 kg/mm2 ± 7.4 |
| BI-RADS density | ||
| Type A | 162 (11.0%) | 330 (11.8%) |
| Type B | 792 (53.7%) | 1560 (55.7%) |
| Type C | 482 (32.7%) | 852 (30.4%) |
| Type D | 31 (2.1%) | 41 (1.5%) |
| Missing | 7 (0.5%) | 21 (0.8%) |
| Ethnicity | ||
| White | 630 (42.7%) | 1127 (40.2%) |
| African-American | 740 (50.2%) | 1425 (50.8%) |
| Other or missing | 104 (7.1%) | 252 (9.0%) |
| Gail lifetime risk score (mean ± SD) | 8.2% ± 4.4 | 8.6% ± 4.3 |
Note: SD = standard deviation; BMI = body mass index; BIRADS = breast imaging reporting and data system.