OBJECTIVES: Primary immune thrombocytopenia (ITP) is an acquired immune-mediated disorder characterized by isolated thrombocytopenia that is associated with increased platelet destruction and impaired platelet destruction. This retrospective study aims to evaluate the treatment outcomes of the first- and second-line agents for adult primary ITP patients in a tertiary hospital in Hong Kong. METHODS: Medical records of patients newly diagnosed with primary ITP between January 2009 and December 2013 at the Prince of Wales Hospital were reviewed. Patient demographics, treatment outcomes, side effect incidence, and other clinical parameters were collected and analyzed. Complete response (CR) was defined as a platelet count ≥100 x10/L and absence of bleeding. RESULTS: A total of 87 patients were evaluated. The median age at diagnosis was 54, and the median platelet count was 22 x10/L at presentation. Complete response was achieved in 54.4% of patients with the first-line therapy with corticosteroid regimens. Comparable CR rates were found among the different steroid groups with high-dose dexamethasone (HD-DEX, 48.6%, N=37), high-dose dexamethasone followed by prednisolone (HD-DEX-PRED, 70.6%, N=17), and prednisolone alone (PRED, 66.7%, N=6). The median duration of CR was significantly shorter in the HD-DEX group (20 days) versus the HD-DEX-PRED (59 days) and PRED (58 days) groups, p =0.022. Complete response rate to second-line steroids regimens after first-line therapy failure was 55.9%. The most common second-line steroid regimen used was prednisolone alone. Steroid side effects, including hyperglycemia, dizziness, dyspepsia, edema, flushing, malaise, and pruritus were reported in 21.7% of treated patients. CONCLUSIONS: Corticosteroids remained as the mainstay of therapy for both first- and second-line management of primary ITP in Hong Kong with acceptable outcomes. Further studies may be warranted to investigate the risk and benefits of various steroid regimens and newer agents.