Urinary beta-thromboglobulin correlates with impairment of renal function in patients with diabetic nephropathy.

Beta-thromboglobulin (beta TG) is a platelet-specific protein and since its concentration in plasma rises when platelets are activated, it has been used as an indicator of platelet involvement in vascular disease. Since platelets might be involved in the pathogenesis of diabetic microvascular disease we measured urinary beta TG in 20 insulin-dependent diabetics with nephropathy and compared the results with those from 20 normal subjects. Measurement of beta TG in urine was undertaken to avoid errors induced by blood sampling and to gain information over a prolonged period using a single assay. Measurements were made of beta TG, beta 2-microglobulin and total protein in urine collected for 24 h and creatinine and beta 2 microglobulin in plasma. Survival of indium-111-labeled platelets was measured in nine patients. Urinary beta TG was significantly (p less than 0.02) increased in the 20 patients compared with 20 normal volunteers (median value 1.3 vs 0.8 microgram/24 h). There was a strong correlation between urinary beta TG excretion and plasma creatinine concentration (r = 0.8, p less than 0.0001) and plasma beta 2-microglobulin concentration (r = 0.9, p less than 0.0001). Urinary beta TG concentration did not correlate with platelet survival. The results indicate that although urinary beta TG is significantly increased in patients with diabetic nephropathy its concentration in urine correlates with indicators of glomerular filtration rather than with a test of platelet activation.