| Value | Category | Cases | |
|---|---|---|---|
| 1 | Within the last 3 years | 22 |
2.5%
|
| 2 | 4-5 years ago | 2 |
0.2%
|
| 3 | more than 5 years ago | 30 |
3.4%
|
| 5 | Never had exam | 828 |
93.9%
|
| 8 | Do not know | 0 |
0%
|
| Sysmiss | 3535 |