Platelet activation in patients with chronic hepatitis C.

＊＊ , ＊＊ ＊ ＊ ＊ ＊＊ Objective: To elucidate the mechanisms of thrombocytopenia in chronic hepatitis C (CHC), we investigated platelet activation in patients with chronic viral liver diseases. Methods: Platelet activation was evaluated with flow cytometry in twenty-five patients with chronic viral hepatitis and 11 patients with liver cirrhosis of viral etiology. Liver biopsies were carried out in all patients. Results: The platelet counts decreased significantly in patients with CHC and in patients with liver cirrhosis compared to controls, but not in patients with chronic hepatitis B (CHB). Patients with CHC had a significantly higher percentage of platelets positive for activation-dependent monoclonal antibodies (MoAbs), and also had a higher percentage of platelet microparticles (PMP), a marker of platelet activation, than patients with CHB. There was a significant correlation between the percentage of PMP and the levels of liver fibrosis markers, such as serum hyaluronate and N-terminal propeptide of type III procollagen (P-III-P), in CHC, suggesting the relationship between platelet activation and liver fibrosis. Platelet activation was markedly enhanced in CHC patients with high histological scores of liver fibrosis. Conclusion: Patients with CHC have increased platelet activation, which may contribute to the occurrence of thrombocytopenia in CHC. Liver fibrosis may play a role in activation of platelets in CHC.