Novartis Pharmaceuticals and a number of participating medical centres/universities in China are conducting this multi-center single-arm study alongside the Institute of Hematology & Blood Diseases Hospital to evaluate the efficacy and safety of eltrombopag to treat thrombocytopenia associated with chronic hepatitis B virus infection. This study includes two parts. In the first part short-term efficacy, safety and tolerability of eltrombopag is evaluated. Any subjects who benefit from eltrombopag treatment (platelet count ≥ 50×109/L) will then be offered the option to enter part two designed to evaluate the long-term efficacy and safety of the drug. This study is open to patients with primary ITP who are over the age of 18 years and were diagnosed with an HBV-infection for at least 6 months prior to the study. They also have to have a platelet count of less than 30K microlitres <30 ×109/L.