The level of serum sialic acid, which is known to reflect atherosclerotic progress and to be related to the incidence of cardiovascular diseases, is increased in patients with diabetes. To elucidate the mechanism of the relation of serum sialic acid to fibrinogen, the relationship between serum sialic acid and markers of blood coagulation activity was investigated in type 2 diabetic patients. The concentration of serum sialic acid showed significant positive correlations with blood platelet count and with plasma concentrations of fibrinogen, D-dimer, thrombin - antithrombin III complex and plasmin-alpha2 plasmin inhibitor complex. These relationships were still significant after adjustment for age, sex, smoking history, body mass index, hemoglobin A(1C), mean arterial pressure and low-density lipoprotein cholesterol. The correlation coefficient of blood fibrinogen with serum sialic acid was still significant after adjustment for D-dimer, thrombin-antithrombin III complex or plasmin-alpha2 plasmin inhibitor complex. On the contrary, blood fibrinogen showed no significant correlation with D-dimer, thrombin-antithrombin III complex or plasmin-alpha2 plasmin inhibitor complex, although an increase in blood fibrinogen is known to be an atherosclerotic risk factor. These results suggest that the serum sialic acid level reflects blood coagulation activity in type 2 diabetic patients and is related to blood fibrinogen level independently of blood coagulation activity. (C) 2002 Lippincott Williams Wilkins.