| Study | Date study author contacted (first) | Date study author provided data (latest) | Data study author provided (short summary) |
| Böhle 2009 | 24 February 2019 | 26 February 2019 | Randomization and allocation concealment method |
| Cao 2011 | 12 February 2019 | 22 February 2019 | Study design |
| Di Lorenzo 2010 | 2 March 2019 | 2 March 2019 | Protocol existence or not |
| Gontero 2013 | 24 February 2019 | 1 March 2019 | Randomization and allocation concealment method |
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