Rapid increase of platelet counts during antiviral therapy in patients with hepatitis C virus infection

Aim: The cause of thrombocytopenia in patients with chronic hepatitis C virus (HCV) infection is multifactorial: hypersplenism, decreased thrombopoietin levels, and myelosuppression induced by HCV. Platelet counts increase after eradication of HCV; however, this mechanism is not fully understood. Therefore, the aim of this study was to determine the influence of these three factors on platelet counts. Methods: We retrospectively analyzed data from 109 HCV-infected patients with platelet counts ≤150 × 10³/μL who achieved viral eradication using interferon-free anti-HCV therapy. Changes in hematological parameters, thrombopoietin levels, HCV titers, and spleen volumes, and the correlations among them were evaluated. Results: HCV RNA levels significantly decreased at 4 weeks after initiating antiviral therapy. Platelet counts rapidly increased at 4 weeks from baseline (120 ± 35 vs. 106 ± 28 × 10³/μL, P < 0.001), and remained at a plateau until 48 weeks after initiating antiviral therapy. Neutrophil counts showed the same pattern. Spleen volume was evaluated in 32 patients and, among them, it decreased in 21 patients, but remained unchanged in seven and increased in four. In addition to patients with decreased spleen volume, patients with unchanged spleen volume showed marginally increased platelet counts. Thrombopoietin levels did not correlate with platelet counts. Conclusions: Platelet counts increased at 4 weeks after starting anti-HCV treatment. Our results suggest that this rapid change was possibly caused by improvement of hypersplenism and HCV-induced myelosuppression resulting from anti-HCV therapy.