| Studies | Jadad questions | Total score | ||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | ||
| Wisham (1953) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Bjerre-Jepsen (1984) | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Wu (1996) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Fan (2005) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Ou (2006) | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Zhu (2006) | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Guan (2007) | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Jiang (2009) | 1 | 0 | 0 | 0 | 0 | −1 | 0 | 0 |
| Zhang (2009) | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 2 |