Kofoed‐Enevoldsen 1987.

Study characteristics
Methods	Study design: retrospective case‐control longitudinal Location: Denmark Time period: 1975 to 1982; December 1985 Outcome: PDR Outcome measurement: incidence
Participants	Number of participants: 220 Diabetes type: T1D Inclusion criteria: group A: persistent proteinuria; group B: matched to group A with regard to gender and year and age at diabetes onset, but free of proteinuria during the study period Exclusion criteria: not reported
Notes	Link to data extraction table, risk of bias assessment, and results: osf.io/qp7b2/?view_only=229b89f8cd7d43538e0aab26340c16cc
Item	Authors' judgement	Support for judgement
Study participation	Unclear	See ‘Notes’ above for link to risk of bias assessment
Study attrition	No	See ‘Notes’ above for link to risk of bias assessment
Prognostic factor measurement	Unclear	See ‘Notes’ above for link to risk of bias assessment
Outcome measurement	Unclear	See ‘Notes’ above for link to risk of bias assessment
Adjustment for other prognostic factors	No	See ‘Notes’ above for link to risk of bias assessment
Statistical analysis and reporting	Unclear	See ‘Notes’ above for link to risk of bias assessment