Table 4

Risk of bias of the included trials

Trial	Sequence generation	Allocation concealment	Blinding	Incomplete outcome data	Selective outcome reporting	Academic bias	Sponsor bias
DCCT/EDIC 19833–46	Adequate	Adequate	Adequate	Unclear	Adequate	Inadequate	Adequate
Franklin et al104	Adequate	Adequate	Inadequate	Adequate	Unclear	Adequate	Adequate
Hvidovre 198268	Unclear	Unclear	Unclear	Adequate	Unclear	Adequate	Unclear
Kroc 1984112–117	Unclear	Unclear	Adequate	Adequate	Unclear	Adequate	Adequate
Linn et al 110	Adequate	Unclear	Unclear	Unclear	Unclear	Adequate	Unclear
Linn et al 69	Unclear	Unclear	Unclear	Unclear	Adequate	Inadequate	Unclear
Microalbuminuria50 51	Unclear	Unclear	Unclear	Adequate	Unclear	Adequate	Adequate
Minnesota DCCT 198383–86	Unclear	Unclear	Unclear	Adequate	Unclear	Adequate	Adequate
Oslo 198673–80	Adequate	Unclear	Adequate	Unclear	Unclear	Adequate	Inadequate
Oxford 1983111	Unclear	Unclear	Adequate	Adequate	Unclear	Adequate	Adequate
Perlman et al105	Unclear	Unclear	Unclear	Adequate	Unclear	Adequate	Adequate
Service et al81	Adequate	Unclear	Unclear	Unclear	Unclear	Adequate	Unclear
Shah et al101	Adequate	Unclear	Adequate	Adequate	Unclear	Adequate	Unclear
Steno 1a 198272 119–121	Unclear	Unclear	Adequate	Unclear	Unclear	Adequate	Inadequate
Steno 1b 198670–72	Unclear	Unclear	Unclear	Adequate	Unclear	Inadequate	Inadequate
Stockholm 198587–98	Adequate	Unclear	Adequate	Unclear	Unclear	Adequate	Inadequate
Verrillo et al82	Unclear	Unclear	Adequate	Unclear	Unclear	Adequate	Unclear
Hershey et al102 and White103	Unclear	Unclear	Unclear	Adequate	Unclear	Adequate	Adequate

DCCT/EDIC, Diabetes Control and Complication Trial/Epidemiology of Diabetes Interventions and Complications; Minnesota DCCT, Minnesota Diabetes Control and Complication Trial.