The project was undertaking by Qilu Hospital of Shandong University and other 13 well-known hospitals in China. In order to report the efficacy and safety of Recombinant Human thrombopoietin combining with Dexamethasone for the treatment of adults with primary immune thrombocytopenia (ITP), compared to High-dose Dexamethasone therapy.

The investigators are undertaking a parallel group, multicentre, randomised controlled trial of 200 primary ITP adult patients from 14 medical centers in China. One part of the participants are randomly selected to receive recombinant human thrombopoietin (given subcutaneously at a dose of 300Units/kg for7-14 consecutive days, following with a flexible dosage depending on platelet count until the 28th day), combining with dexamethasone (given intravenously at a dose of 40 mg per day for 4days, the others are selected to receive high-dose of dexamethasone treatment (given intravenously at a dose of 40 mg daily for 4 days). Platelet count was evaluated before and after treatment, in order to report the conversion ratio of primary ITP to chronic ITP.

Inclusion Criteria:

1. Meet the diagnostic criteria for immune thrombocytopenia.
2. Untreated hospitalized patients, may be male or female, between the ages of 18 ~ 80 years.
3. To show a platelet count < 30×10^9/L, and with bleeding manifestations.
4. Eastern Cooperative Oncology Group（ECOG）performance status ≤ 2.
5. Willing and able to sign written informed consent.

Exclusion Criteria:

1. Received chemotherapy or anticoagulants or other drugs affecting the platelet counts within 3 months before the screening visit.
2. Received high-dose steroids or [2] intravenous immunoglobulin transfusion(IVIG)in the 3 weeks prior to the start of the study.
3. Current HIV infection or hepatitis B virus or hepatitis C virus infections.
4. Severe medical condition (lung, hepatic or renal disorder) other than ITP. Unstable or uncontrolled disease or condition related to or impacting cardiac function (e.g., unstable angina, congestive heart failure, uncontrolled hypertension or cardiac arrhythmia)
5. Female patients who are nursing or pregnant, who may be pregnant, or who contemplate pregnancy during the study period.
6. Have a known diagnosis of other autoimmune diseases, established in the medical history and laboratory findings with positive results for the determination of antinuclear antibodies, anti-cardiolipin antibodies, lupus anticoagulant or direct Coombs test.
7. Patients who are deemed unsuitable for the study by the investigator.