Table 2 Risk of bias of included studies
Study | Random sequence generation | Allocation concealment | Incomplete outcome data | Selective reporting |
|---|---|---|---|---|
Berry 2002 Study 1 [10] | Unclear | Unclear | Low | Low |
Berry 2002 Study 2 [10] | Unclear | Unclear | Low | Low |
Berry 2003 Study 1 [11] | Unclear | Unclear | Low | Low |
Berry 2003 Study 2 [11] | Unclear | Unclear | Low | Low |
Berry 2004 [12] | Unclear | Unclear | Low | Low |
Berry 2006 [13] | Unclear | Unclear | Unclear | Low |
Knapp 2004 [14] | Unclear | High | Unclear | Low |
Knapp 2009a [8] | Low | Low | Unclear | Low |
Knapp 2009b Study 1 [8] | Low | Low | Unclear | Low |
Knapp 2009 Study 2 [15] | Low | Low | Unclear | Low |