Indium-labeled scintigraphy to predict splenectomy response in ITP: back to the future

Splenectomy, a curative option for immune thrombocytopenia (ITP), achieves long-term remission in 50 to 70% of patients but has been de-emphasized recently because it carries well-described lifelong risks: overwhelming sepsis and venous and arterial thrombosis. It is particularly frustrating for patient and physician alike if splenectomy conveys these risks and yet is unsuccessful in normalizing the platelet count. Identifying reliable predictors of splenectomy response is therefore critical, especially given the availability of modern, less invasive, efficacious, albeit less curative, pharmacologic therapies. Indium-labeled autologous platelet scintigraphy (ILAPS) originally emerged in the 1970s as a diagnostic imaging technique to measure platelet destruction sites (spleen vs. liver). Patients with predominantly splenic platelet sequestration on ILAPS were thought to be more likely to respond favorably to splenectomy than those with hepatic or mixed sequestration patterns. Previous studies e.g. meta-analyses showed strong correlations (odds ratios ∼14–15) favoring splenic sequestration as a predictor of splenectomy success. Recent studies from Australia, Spain, France, the Netherlands and the UK, conducted since the most recent metanalysis, further reaffirm ILAPS’s predictive value for durable splenectomy response and relapse-free remission. Recent studies have also re-evaluated the utility of previously discarded scintigraphy using homologous (donor) platelets, as well as biomarkers such as platelet-specific glycoprotein antibodies, platelet desialylation and complement levels to enhance post-splenectomy response prediction in conjunction with ILAPS. This narrative review summarizes historical and technical aspects of ILAPS, older and more recent clinical studies, and limitations as well as opportunities for optimizing this technique.