Avatrombopag in the Treatment of Pediatric Immune Thrombocytopenia

Inclusion Criteria: * Age 6-18 years old (including both ends), male and female; * Diagnosed with primary immune thrombocytopenia (ITP); * Patients who had previously received eltrombopag treatment and then converted to avatrombopag treatment because of ineffectiveness (platelet count \< 30×10\^9/L after eltrombopag treatment, or platelet count increased less than 2 times of the basic value, or bleeding) or large platelet fluctuation or due to patient preference, economic reasons and other reasons; * Cardiac function of the New York Society of Cardiac Function ≤ 2; * Understand the study procedure and voluntarily sign the informed consent. Exclusion Criteria: * Secondary thrombocytopenia caused by various reasons, such as connective tissue disorders, bone marrow hematopoietic failure disease, myelodysplastic syndrome, malignancy, drugs, inherited thrombocytopenia, common variable immune deficiency, lymphoma, etc.; * Subjects with primary disease of important organs (liver, kidney, heart, etc.), or with immune system diseases; * Subjects who are known to be allergic to avatrombopag or any of its excipients; * Subjects who had used rituximab within the last 3 months; * Subjects who underwent splenectomy within the last 3 months； * Subjects with a history of abnormal platelet aggregation that may affect the reliability of platelet count measurements； * Any medical history or condition that the investigator deems unsuitable for participation in the study.