Thrombocytopenia is one of the most common laboratory manifestations of disseminated intravascular coagulation (DIC). To investigate whether thrombocytopenia in DIC is indeed due to platelet consumption, we measured the plasma levels of glycocalicin, a proteolytic fragment of the platelet membrane glycoprotein (GP) Ib alpha, a component of the GPIb/IX complex, in patients with solid tumors either with DIC(n=18) or without DIC (n=18). Patients with DIC had significantly elevated levels of glycocalicin(2.53 +/- 1.59 mg/1;n=18,p<0.05) compared to those without DIC (1.50 +/- 0.41 mg/1;n=18), indicating enhanced platelet consumption, or destruction, in patients with DIC. However, glycocalicin concentrations had a wide range (0.18-5.74 mg/1), and 3 DIC patients had levels lower than the normal lower limit. These findings suggest that, in patients with DIC, thrombocytopenia is not always due to increased platelet consumption, but it may be due to decreased production of platelets. Determination of plasma glycocalicin concentrations is an easy way to identify thrombocytopenia, due to bone marrow insufficiency in these patients.