Type IV collagen serum and vitreous fluid levels in patients with diabetic retinopathy

We compared the levels of type IV collagen (IV-C) in vitreous fluid and serum and the levels of glycosylated haemoglobin in 47 patients with proliferative diabetic retinopathy (DR) and 21 patients with non-inflammatory retinopathies. Levels of IV-C were found to be higher in the vitreous fluid in patients with DR than in patients with non-inflammatory retinopathy (53.2 +/- 14.9 microg/l versus 14.7 +/- 4.5 microg/l). Serum levels were likewise higher in patients with DR (349.7 +/- 106.2 microg/l versus 97.7 +/- 13.1 microg/l) as were glycosylated haemoglobin levels (8.3 +/- 0.3% versus 5.2 +/- 0.4%). In addition, levels of type IV collagen in the vitreous fluid were found to be higher in the patients who had been diabetic for > or = 10 years than in patients who had been diabetic for < 10 years (54.8 +/- 15.5 microg/l versus 16.8 +/- 4.6 microg/l). We conclude that accumulation of vitreous fluid IV-C may relate to high levels of glycosylated haemoglobin and long duration of diabetes. This suggests that the concentration of IV-C in vitreous fluid, and possibly also the serum levels of IV-C, reflects the progression of DR. Further investigation is needed to verify this and to investigate whether or not measuring IV-C levels is a useful means to assess therapeutic effects and/or prognosis of diabetic microangiopathy.