| Value | Category | Cases | |
|---|---|---|---|
| 0 | took the test every 2 or 3 years | 6 | 
                                    
                                    0.3%
                                 | 
| 1 | only once | 1574 | 
                                    
                                    79.3%
                                 | 
| 2 | every year | 113 | 
                                    
                                    5.7%
                                 | 
| 3 | every 6 months | 96 | 
                                    
                                    4.8%
                                 | 
| 4 | every 3 months | 74 | 
                                    
                                    3.7%
                                 | 
| 5 | took the test more than 3 times | 19 | 
                                    
                                    1%
                                 | 
| 6 | other | 6 | 
                                    
                                    0.3%
                                 | 
| 7 | took the test 2 times | 72 | 
                                    
                                    3.6%
                                 | 
| 8 | took the test 3 times | 26 | 
                                    
                                    1.3%
                                 | 
| 11 | .Z | 6253 |