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Reasons for excluding papers
| Reason for exclusion | Number of papers |
| Before/after studies | 17 |
| Brief report given only | 6 |
| Case control study | 5 |
| Phase II trial (no control arm) | 4 |
| Randomisation not mentioned in full text | 2 |
| Allocated by patients' choice | 1 |
| Allocated by patients' economic status | 1 |
| Total | 36 |
