Indium-labelled autologous platelet sequestration studies predict response to splenectomy in immune thrombocytopenia: an Australian experience

Background: Splenectomy is an effective intervention in primary immune thrombocytopenia (ITP). Attempts to define pre-clinical predictors of platelet response to splenectomy are inconsistent. Based on international studies defining the likelihood of platelet response using platelet sequestration, patients with relapsed/refractory ITP being considered for splenectomy at a regional Australian hospital were assessed with 111indium-labelled autologous platelet sequestration (ILAPS) studies. Aims: To audit the use of ILAPS in an Australian setting and define its role in predicting response to splenectomy. Methods: A retrospective review of all patients referred for an ILAPS study at a regional hospital was performed. Results for each patient were expressed as an ‘R’ value (spleen/ liver uptake ratio) to quantify the platelet sequestration pattern and outcome post-splenectomy, based on platelet counts. Results: A total of 45 patients was identified: 13 underwent splenectomy and 32 were medically managed. Patients with favourable ILAPS scans (pure or predominant splenic sequestration) demonstrated a superior response post-splenectomy (100% overall response rate (ORR); 83.5% complete remission (CR)) compared with those with unfavourable ILAPS scans (mixed or pure hepatic sequestration) (71.4% ORR; 57.1% CR) over 12 months. Conclusions: The use of ILAPS in the Australian setting is feasible and this experience confirms larger international studies demonstrating its utility as a predictor of response to splenectomy in ITP. An unfavourable ILAPS scan could be considered a negative predictor of response prompting consideration for other emerging ITP treatments such as thrombopoietin-receptor agonists or B-cell depleting therapy such as Rituximab