| Sample | At 3 months | At 6 months | At 12 months | |
| Our Study 2011 | n = 70 | 53.84% | 79% | 85.48% |
| Chattopdhyay et al., 2011 | n = 42 | 54% | 91.54% | 92.25% |
| Kaunitz et al., 2010 | n = 82 | 62% | 71% | 87% |
| Endrikal et al., 2009 | n = 20 | 78% | 94% | 94% |
| Utman et al., 2011 | n = 60 | - | 67% | 85% |
| Xiao et al., 2003 | n = 34 | - | 79% | 84% |