ObjectiveHigh vitreous levels of soluble (s)CD163 have been demonstrated in severe diabetic retinopathy (DR). The aim of this study was to explore the predictive values of plasma sCD163 and glycated haemoglobin (HbA1c) for DR progression in adults with type 1 diabetes. Methods and analysesThe study design was prospective. Fundus photography performed in 2009 and at follow-up (& LE;12 years later) were compared after being categorised according to the International Clinical Diabetic Retinopathy Disease Severity Scale. 'DR progression at least one level' was calculated. In 2009, data collection (sex, age, diabetes duration, metabolic variables, serum creatinine, macroalbuminuria and lifestyle factors) and biochemical analyses were performed. Plasma sCD163 and HbA1c were divided into quartiles. Logistic regression analyses were performed. ResultsThe prevalence of DR in 2009 versus at follow-up in 270 participants (57% male) were: no apparent 28% vs 18%; mild 20% vs 13%; moderate 24% vs 26%; severe 11% vs 13%; and proliferative DR 17% vs 30% (p<0.001). DR progression occurred in 101 (45%) patients. HbA1c & GE;54 mmol/mol (& GE;7.1%) (>1st quartile) (adjusted odds ratio (AOR) 3.8, p<0.001) and sCD163 & GE;343 ng/mL (>1st quartile) (AOR 2.6, p=0.004) were independently associated with DR progression. The associations with DR progression increased significantly from the first to the fourth quartile for HbA1c (AORs: 1; 2.5; 3.6; 7.4), but not for sCD163 (AORs: 1; 2.9; 2.4; 2.4). ConclusionPlasma sCD163 may constitute a valuable biomarker for DR progression in addition to and independent of the well-established biomarker HbA1c.