Does Increased Platelet Aggregation Have a Prognostic Value in the Deterioration of Background Diabetic Retinopathy?

Summary

Many case-control studies have suggested that increased platelet aggregation (PA) could be involved in the pathogenesis of diabetic microangiopathy. However, longitudinal data are needed to support this hypothesis. We consider here such an approach in the placebo group (93 diabetic patients) of a controlled clinical trial on the effect of PA inhibitors in the treatment of diabetic retinopathy (Damad program). We have measured spontaneous PA and PA induced by ADP, collagen and arachidonic acid before treatment and yearly during a 3-year period. The assessment of retinopathy was based on the changes in the number of microaneurysms present in the macular field as seen on fluorescein angiograms during follow-up. PA was estimated by maximal decrease in optical density. The lowest ADP concentration still able to induce irreversible aggregation was also determined. No significant correlations between any baseline PA measurements and end point criterion were found (all correlation coefficients lower than 0.20). No significant changes in mean PA were observed during follow-up. Within-subject variation of PA was markedly large accounting for 61% to 98% of the total variance of various measurements. Allowances for the main characteristics of diabetes made no substantial difference to the results. These negative findings can be partly attributed to the lack of reliability of PA tests. In our study, we conclude that PA tests are not useful measures for the prediction of evolution of background diabetic retinopathy.

• References

• 1 McMillan DE. Deterioration of the microcirculation in diabetes. Diabetes 1975; 24: 944-957
• 2 Heath M, Bridgen WD, Canever JV, Pollock J, Hunter PR, Kesley J, Bloom A. Platelet adhesiveness and aggregation in relation to diabetic retinopathy. Diabetologia 1971; 1: 308-315
• 3 Bensoussan D, Levy-Toledario S, Passa P, Caen J, Canivet J. Platelet hyperaggregation and increased level of von Willebrand factor in diabetes with retinopathy. Diabetologia 1975; 11: 307-312
• 4 Colwell JA, Halushka PV, Saiji K, Levin J, Sagel J, Nair R. Altered platelet function in diabetes mellitus. Diabetes 1976; 27: 826-831
• 5 Scarabin PY, Samama M. Damad research study group. Effect of age on ADP induced platelet aggregation in diabetic and non diabetic subjects. Thromb Res 1981; 22: 687-692
• 6 Bern MM. Platelet function in diabetes mellitus. Diabetes 1978; 27: 342-362
• 7 Paton RC, Passa Ph. Platelets and diabetic vascular disease. Diabete Metabolisme 1983; 9: 306-312
• 8 Ostermann H, Van de LooJ. Factors of the hemostatic system in diabetic patients. A survey of controlled studies. Haemostasis 1986; 16: 386-416
• 9 Groupe d’étude Damad. Essai controlé de ľaspirine et de ľassociation aspiririe et dipyridamole sur ľévaluation de la retinopathie diabétique. I. Protocole général. Diabète Métabolisme 1982; 8: 91-96
• 10 Groupe d’étude Damad. Essai controlé de ľaspirine et de ľassociation aspirine et dipyridamole sur ľévaluation de la rétinopathie diabétique. II. Protocole ophtalmique. Diabète Métabolisme 1982; 8: 307-311
• 11 The Damad study group. Effect of aspirin alone and aspirin plus dipyridamole in early diabetic retinopathy. A multicenter randomised controlled clinical trial. Diabetes 1989; 38: 491-498
• 12 Born G VR. Aggregation of blood platelets by adenosin diphosphate and its reversal. Nature 1962; 194: 927-929
• 13 Baudoin C, Maneschi FS, Quentel G, Soubrane G, Hayes T, Jones G, Coscas G, Kohner EM. Quantitative evaluation of fluorescein angiograms: microaneurysms counts. Diabetes 1983; 32: 8-13
• 14 Snedecor GW, Cochran WG. Statistical Methods. Iowa State Univ. Press; 1967
• 15 Juhan I, Buonocore M, Jouve RS, Vague Ph, Moulin JP, Vialettes B. Abnormalities of erythrocyte deformability and platelet aggregation in insulin-dependent diabetics corrected by insulin in vivo and in vitro. Lancet 1982; I: 535-537
• 16 Scarabin PY, Strain L, Ludlam CA, Jones J, Kohner EM. Damad study group. Reliability of a single p-thromboglobulin measurement in a diabetic population: importance of PGE1 in anticoagulant mixture. Thromb Haemostas 1987; 57: 201-204
• 17 Engerman RL. Pathogenesis of diabetic retinopathy. Diabetes 1989; 38: 1203-1206