Effect of panretinal photocoagulation on serum levels of laminin in patients with diabetes: a prospective study.

Background/aim: Laminin, a major specific non-collagenous glycoprotein of basement membrane, has been proposed as an index of diabetic retinopathy and high serum concentrations have been reported in patients with proliferative diabetic retinopathy. On the other hand, panretinal photocoagulation (PRP) prevents the progression of severe diabetic retinopathy and reverses preretinal neovascularisation. The aim of the study was to investigate the effect of PRP on serum levels of laminin in patients with diabetes.

Methods: 20 patients with diabetes undergoing PRP and 15 patients with mild or moderate non-proliferative diabetic retinopathy in whom a PRP was not performed were included in the study. Serum laminin-P1 (Lam-P1), the largest pepsin resistant fragment of laminin, was determined by radioimmunoassay in each patient before starting PRP and 3 months after it was accomplished. Similarly, a baseline and a 4 month sample were analysed in the non-photocoagulated controls.

Results: Serum Lam-P1 concentrations obtained 3 months after PRP were significantly lower when compared with the initial values (1.62 (SD 0.36) U/ml v 1.91 (0.37) U/ml; p <0.001). A decrease of serum levels of Lam-P1 could be seen in all patients. By contrast, in those patients with mild or moderate non-proliferative diabetic retinopathy in whom a PRP was not performed, no significant changes were detected in serum Lam-P1 concentrations (1.72 (0.20) U/ml v 1. 74 (0.17); p=0.250).

Conclusion: PRP decreases serum Lam-P1 levels in patients with severe diabetic retinopathy. Thus, the studies addressed to evaluate the usefulness of Lam-P1 as a marker of diabetic retinopathy should consider previous PRP as an influencing factor. Finally, our results suggest that retinal source of Lam-P1 strongly contributes to serum Lam-P1 in patients with severe diabetic retinopathy.