The interpretation of platelet kinetic studies for the identification of sites of abnormal platelet destruction

Abstract

Summary. The kinetics of platelets labelled with 111In have been studied in a series of 175 subjects including 18 normal volunteers, and 12 patients with idiopathic thrombocytopenic purpura (ITP), but excluding patients in whom there was scintigraphic evidence of intravascular platelet consumption. From analysis of the kinetics, the following parameters were calculated: splenic blood flow (SBF), intrasplenic platelet transit time (t), splenic platelet pool capacity (expressed as a percentage of the total circulating platelet population), the fraction of the dose of labelled platelets ultimately destroyed in the spleen and the mean platelet life span (MPLS). SBF increased with increasing spleen size up to values of 25% total blood volume (TBV) per min. Some patients with immune complex related diseases were identified with elevated SBF (up to 24% TBV min−1) but without significant splenomegaly, Patients with cardiac decompensation had reduced SBF relative to spleen size. t showed no relationship with spleen size. It tended to fall in patients who had high SBF relative to spleen size and to rise in those with low SBF relative to spleen size; i.e. it was inversely related to splenic perfusion (flow per unit tissue volume). The splenic platelet pool capacity is dependent on platelet input (SBF) and splenic platelet clearance (reciprocal of t), and showed a close relationship with spleen size. When all subjects except those with ITP were considered, splenic platelet destruction showed a good correlation (r = 0.70, n = 42, P<0.001) with the splenic platelet pooling capacity. The ratio of the fraction of platelets destroyed in the spleen to the fraction pooling there, the D/P ratio, was approximately unity and did not appear to vary with MPLS, spleen size or the patient's condition, except in ITP where it varied between about 0.5 and 2. This variation in ITP was thought to be the result of an

Splenectomy for immune thrombocytopenia: down but not out

“…Indium-labeled autologous platelet scanning (ILAPS), in which indium-111 labeled autologous platelets are infused into the patient and subsequent scintigraphy reveals the site of platelet clearance, 36 emerged as a promising predictor of splenectomy response in the 1980s but has not been widely adopted. …”

The management of thrombocytosis

“…the splenic blood flow and the intrasplenic platelet transit time. Finally, it has been demonstrated that the splenic platelet pool size and the splenic blood flow increase concomitantly with increasing spleen size, and that the splenic blood flow can be modulated by infusion of adrenaline and isoprenaline (26)(27)(28)(29).…”

Evidence-Based Mini-Review: Is Indium-Labeled Autologous Platelet Scanning Predictive of Response to Splenectomy in Patients With Chronic Immune Thrombocytopenia?

“…It has been proposed that patients with purely or predominantly splenic sequestration determined by ILAPS may be more likely to respond to splenectomy than those exhibiting hepatic, mixed, or diffuse patterns. 4 To evaluate the potential of ILAPS to predict response to splenectomy, we performed a comprehensive literature review of all studies in which ILAPS was performed prior to splenectomy in patients with ITP.A search of the PubMed database limited to English language references was conducted by combining the MeSH (Medical Subject Heading) term "indium" with the keywords "ITP," "immune thrombocytopenic purpura," "idiopathic thrombocytopenic purpura," and "autoimmune thrombocytopenia" between 1950 and June 30, 2010. This strategy yielded 51 citations.…”

“…It has been proposed that patients with purely or predominantly splenic sequestration determined by ILAPS may be more likely to respond to splenectomy than those exhibiting hepatic, mixed, or diffuse patterns. 4 To evaluate the potential of ILAPS to predict response to splenectomy, we performed a comprehensive literature review of all studies in which ILAPS was performed prior to splenectomy in patients with ITP.…”