| Trial | Sequence generation (selection bias) | Allocation concealment (selection bias) | Blinding of participants and personnel (performance bias) | Blinding of outcome assessors (detection bias) | Completeness of outcome data (attrition bias) | Selective reporting (reporting bias) | Academic bias | Sponsor bias | |
|---|---|---|---|---|---|---|---|---|---|
| ADOPT, 2006 (20)– (26) | Low | Low | Low | Low | Low | Low | Low | High | |
| Campbell et al., 1994 (27) | Unclear | Unclear | High | High | Low | Unclear | Low | Unclear | |
| Collier et al., 1989 (28) | Unclear | Unclear | High | High | Unclear | Unclear | Low | High | |
| DeFronzo et al., 1995 (29) | Unclear | Unclear | Unclear | Unclear | Unclear | Unclear | Low | High | |
| Derosa et al., 2004 (42) | Unclear | Unclear | High | High | Low | Unclear | Low | Unclear | |
| Hermann et al., 1991a (30) | Low | Unclear | High | High | Unclear | Unclear | Low | High | |
| Hermann et al., 1991b (31)– (34) | Low | Low | Low | Low | Low | Low | High | High | |
| Kamel et al., 1997 (35) | Unclear | Unclear | Unclear | Unclear | Unclear | Unclear | Low | Unclear | |
| Lawrence et al., 2004 (36) | Unclear | Unclear | High | Low | Low | Unclear | Low | High | |
| Tang et al., 2004 (41) | Unclear | Unclear | High | High | Unclear | Unclear | Low | Low | |
| Tessier et al., 1999 (37) | Unclear | Unclear | High | High | Low | Unclear | Low | High | |
| Tosi et al., 2003 (38) | Low | Low | Low | Low | Unclear | Low | Low | High | |
| UKPDS 34, 1998 (2), (39), (40) | Low | Low | High | Low | Unclear | High | Low | High | |
| Yamanouchi et al., 2005 (43) | Low | Low | High | High | Low | Unclear | Low | Unclear | |
Note: ADOPT = A Diabetes Outcome Progression Trial, UKPDS = United Kingdom Prospective Diabetes Study. *The Cochrane risk-of-bias tool was used to assess the risk of bias for each study. Low risk = bias, if present, is unlikely to alter the results seriously, unclear risk = bias raises some doubt about the results, high risk = bias may alter the results seriously. (10)