Table 5. Non-responders at 6 months in the doxycycline and penicillin group who had completed 6 months of follow-up.
| Non-responder at 6 months | Doxycycline N = 45 | Penicillin N = 75 | |
| 3-month follow-up (−)/6-month follow-up (−) | Reinfection§ | 0 | 0 |
| Treatment failure§§ | 6 | 15 | |
| 3-month follow-up (−)/6-month follow-up (+) | Reinfection | 1 | 2 |
| Treatment failure | 9 | 13 | |
| 3-month follow-up (+)/6-month follow-up (−) | Reinfection | 1 | 1 |
| Treatment failure | 13 | 11 | |
| 3-month follow-up (+)/6-month follow-up (+) | Reinfection | 1 | 12 |
| Treatment failure | 14 | 21 | |
| Total cases of reinfection, n (%)a | 3 (6.7) | 15 (20.0) | |
| Total cases of treatment failure, n (%) | 42 (93.3) | 60 (80.0) | |
Note: "3 month follow-up (−)" indicates patients had no follow-up of RPR titer at 3 months of treatment, while " 3 month follow-up (+)"indicates patients had follow-up of RPR titer; "6 month follow-up (−)" indicates patients had no follow-up of RPR titer at 6 months of treatment, while "6 month follow-up (+)" indicates patients had follow-up of RPR titer.
Re-infection: development of new symptoms of primary syphilis and secondary syphilis; or a 4-fold or greater increase of RPR titer after ever achievement of 4-fold or greater decline following treatment.
Treatment failure: failure of RPR titer to decrease by 4 folds or greater, or receipt of another course of treatment without demonstrated serological response throughout the follow-up period.
There was 1 case of secondary syphilis in the doxycycline group, while there were 2 cases of primary, 3 secondary, and 2 primary as well as secondary syphilis in the penicillin group.