Course of immune thrombocytopenia according to the site of platelet destruction identified by indium-111 platelet scintigraphy

Abstract

In primary immune thrombocytopenia (ITP), predictors of disease evolution and treatment response are needed. Data based on the site of platelet destruction are scarce. We performed a retrospective single-centre study of adult patients with primary ITP undergoing at least one Indium-111 platelet scintigraphy (IPS) between 2009 and 2018. Thirty-three patients had isolated hepatic platelet destruction (H-group), and 97 isolated splenic destruction (S-group). Median age at diagnosis (p < 0.001), proportion of associated cardiovascular (p < 0.001), organ-specific autoimmune diseases (p = 0.02), dependence on steroids (p = 0.003) and failure to rituximab (p = 0.01) were higher and relapse more frequent (p = 0.03) in H-group compared to non-splenectomized patients in S-group. Splenectomy was only performed in patients from S-group (as patients with hepatic sequestration are not splenectomized in our centre): 79% were in relapse-free remission at the end of a median 3.4-year post-IPS follow-up, 16% relapsed. In multivariate analyses, only a history of organ-specific autoimmune or inflammatory disease was significantly associated with hepatic sequestration (OR = 4.3, 95% CI = 1.2-15, p = 0.02). Patients with isolated hepatic sequestration were older, had more cardiovascular events and organ-specific autoimmune diseases, greater dependence on steroids, more relapses and a decreased response rate to rituximab suggesting an increased refractoriness to immunomodulatory therapies. Patients with isolated splenic sequestration responded well to splenectomy.

Keywords: TPO receptor agonists; immune thrombocytopenia; indium‐111 platelet scintigraphy; rituximab; sequestration pattern; splenectomy.

FIGURE 1

Time points of injection and blood draws to assess platelets clearance. Briefly, platelet kinetics were assessed using a 7‐mL blood sample obtained 10 min and 1 h after the administration of autologous Indium‐111‐labelled platelets, followed by daily sampling until the radioactivity signal decreased to 10%; the site of platelet destruction was identified using a gamma camera focused on the liver and spleen; and radioactivity was measured 30 min after the injection of labelled platelets, and daily during 4 days. Four parameters were measured: Platelet lifespan in plasma, spleen/hepatic ratio at 24 or 48 h depending on platelet lifespan, splenic capture index and site of platelet destruction.

FIGURE 2

Study flowchart. Platelet sequestration was not detected in 11 patients because of a possible technical mishap during IPS, a high (with no platelet destruction) or a very low platelet count, or, in case of a low platelet count, a consumption of the remaining platelets for haemostasis, another mechanism of platelet destruction than phagocytosis by the mononuclear phagocyte system in the spleen or liver or another diagnosis than ITP.