| Value | Category | Cases | |
|---|---|---|---|
| 1 | Once a year | 253 |
58.7%
|
| 2 | Once every 2 years | 160 |
37.1%
|
| 3 | More than a 2 year gap between treatments | 10 |
2.3%
|
| 8 | Unknown | 8 |
1.9%
|
| Sysmiss | 510 |