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Refractoriness to platelet transfusion is a common clinical problem encountered by the transfusion medicine specialist. It is well recognized that most causes of refractoriness to platelet transfusion are not a consequence of alloimmunization to human leukocyte, platelet-specific, or ABO antigens, but are a consequence of platelet sequestration and consumption. This review summarizes the clinical factors that result in platelet refractoriness and highlights recent data describing novel biological mechanisms that contribute to this clinical problem., Highlights • Non-alloimmune pathophysiologic mechanisms lead to increased platelet consumption or sequestration in the majority of patients with thrombocytopenia and/or refractoriness to platelet transfusion. • Splenomegaly is associated with increased splenic platelet sequestration. • Sepsis can promote platelet consumption through effects on platelet activation, adhesion, apoptosis, and desialylation. • Neutrophil extracellular traps, endothelial activation, and decreased ADAMTS13 activity can also contribute to platelet consumption in sepsis. • There is an unmet need for effective strategies to improve hemostasis and the efficacy of platelet transfusion in patients with non-alloimmune causes of thrombocytopenia and/or refractoriness to platelet transfusion.

The spleen, in addition to its role in immunity, plays key roles in erythrocyte maintenance and platelet sequestration. Loss of the spleen via splenectomy occurs in approximately 6.4 to 7.1 per 100 000 people per year globally, commonly as a life-saving emergency procedure in trauma and a therapeutic procedure in hematological and hematological malignant conditions. It is associated with increased risk of life-threatening infection and thromboembolism, presumably via loss of splenic function, but the underlying mechanisms behind post-splenectomy thromboembolism are unclear. The splenectomized individual has a two-fold risk of thromboembolism as compared to non-splenectomized individuals and the risk of thromboembolism is elevated both post-operatively and in the longer term. Although those splenectomized for hematological conditions or hematological malignant conditions are at highest risk for thromboembolism, an increase in thromboembolic outcomes is also observed amongst individuals splenectomized for trauma, suggesting underlying disease state is only a partial factor. Although the physiological role of the splenic platelet pool on platelets is unclear, platelet changes after splenectomy suggest that the spleen may play a role in maintaining platelet quality and function. In hypersplenic conditions, sequestration can increase to sequester up to 72% of the total platelet mass. Following splenectomy, a thrombocytosis is commonly seen secondary to the loss of the ability to sequester platelets. Abnormal platelet quality and function have been observed as a consequence of splenectomy. These platelet defects seen after splenectomy may likely contribute to the increase in post-splenectomy thromboembolism. Here we draw upon the literature to characterize the post-splenectomy platelet and its potential role in post-splenectomy thromboembolism.

PURPOSE OF REVIEW This review highlights advances in liver xenotransplantation, focusing on immunologic barriers and mechanisms underlying graft failure and recipient demise, and discussion of recent in-vivo results. RECENT FINDINGS Pig to primate models of liver xenotransplantation have been plagued by thrombocytopenia, anemia, and coagulopathy. It is now known that platelet sequestration is mediated by liver sinusoidal endothelial cells and Kupffer cells in part by asialoglycoprotein receptor 1-driven mechanisms. Xenoantigens, specifically N-glycolylneuraminic acid, play a role in graft injury as well as red blood cell consumption. Finally incompatibilities between coagulation cascade molecules contribute to lethal coagulopathy, but can be counteracted with genetic modifications and coagulation factor supplementation. Survival has markedly increased with this strategy. SUMMARY An increased understanding of the cellular mechanisms responsible for failure of in-vivo pig to primate liver xenotransplant models has led to improved outcomes, and this recent success supports initial clinical application.

Splenectomy is the only potentially curative treatment for chronic immune thrombocytopenic purpura (ITP) in adults. However, one-third of the patients relapse without predictive factors identified. We evaluate the predictive value of the site of platelet sequestration on the response to splenectomy in patients with ITP. Eighty-two consecutive patients with ITP treated by splenectomy between 1992 and 2013 were retrospectively reviewed. Platelet sequestration site was studied by (111)Indium-oxinate-labeled platelets in 93% of patients. Response to splenectomy was defined at last follow-up as: complete response (CR) for platelet count (PC) ≥100 × 10(9)/L, response (R) for PC≥30 × 10(9)/L and100 × 10(9)/L with absence of bleeding, no response (NR) for PC30 × 10(3)/L or significant bleeding. Laparoscopic splenectomy was performed in 81 patients (conversion rate of 16%), and open approach in one patient. Median follow-up was 57 months (range, 1-235). Platelet sequestration study was performed in 93% of patients: 50 patients (61%) exhibited splenic sequestration, 9 (11%) hepatic sequestration and 14 patients (17%) mixed sequestration. CR was obtained in 72% of patients, R in 25% and NR in 4% (two with splenic sequestration, one with hepatic sequestration). Preoperative PC, age at diagnosis, hepatic sequestration and male gender were significant for predicting CR in univariate analysis, but only age (HR = 1.025 by one-year increase, 95% CI [1.004-1.047], p = 0.020) and pre-operative PC (HR = 0.112 for100 versus=100, 95% CI [0.025-0.493], p = 0.004) were significant predictors of recurrence-free survival in multivariate analysis. Response to splenectomy was independent of the site of platelet sequestration in patients with ITP. Pre-operative platelet sequestration study in these patients cannot be recommended.

Thrombocytopenia is common in chronic liver disorders, and may be due to a variety of non-immune and immune mechanisms. The latter include clearance of immune complexes, or increased platelet sequestration driven from an antigen-antibody immune response. A number of case observations led to the assumption that autoimmune thrombocytopenia (AITP) is a common feature in HCV infected individuals, while it is rare in non-immune chronic liver disease. Clinically, the differentiation of AITP from other forms of thrombocytopenia can influence therapeutic measures. Therefore, in HCV infection it is mandatory to disclose the pathomechanisms of thrombocytopenia in each case individually. In this article we will discuss the various pathomechanisms that may result in thrombocytopenia in HCV infection, review the current literature with reference to an increased occurrence of AITP in HCV infected patients, and how laboratory tools may assist in the diagnosis. Finally, we will address some of the questions that need to be answered to get a clearer impression of laboratory and clinical parameters pertaining to a possible association of AITP in HCV.

and theetiology of this thrombocytopenia is often multifactorial.The most frequent etiologies include hemodilution,increased platelet consumption (secondary to tissue trauma,bleeding, and disseminated intravascular coagulopathy),increased platelet destruction by immune mechanisms orby extracorporeal circulation, decreased platelet produc-tion, increased platelet sequestration, the laboratory artifactof pseudothrombocytopenia, or a combination of several ofthese factors.

The significance of the site of platelet sequestration in determining the indication for splenectomy in idiopathic thrombocytopenic purpura (ITP) is a controversial subject. However, most of the negative conclusions are based on 51chromium labelling of homologous platelets. We report here the results of an analysis of 222 cases in which the kinetic study of 111indium-oxinate-labelled autologous platelets was performed under homogeneous technical conditions. 103 of these patients subsequently underwent splenectomy. This study demonstrates that the site of platelet sequestration in active ITP constitutes a variable independent of the patient's age, history of the disease and its severity (platelet count, lifespan). The sequestration site is a good predictive element of the short-term efficacy of splenectomy (71/76 cases with splenic sequestration obtained a platelet count exceeding 100 x 10(9)/l versus 7/13 cases with mixed sequestration and 1/14 cases with hepatic sequestration), and the long-term results (6 months to 5 years after splenectomy) do confirm the clinical value of this study.

Synthetic vascular grafts have a thrombogenic surface which plays a role in graft failure. Systemic pharmacologic interventions have been used to lower platelet sequestration onto the graft surface but are associated with side effects. In this communication we describe the results of a new therapeutic principle of applying forskolin, a powerful cyclic adenosine monophosphate stimulator (cAMP) to the inner surface of PTFE vascular grafts. The grafts were evaluated with Indium-III-oxine labelled platelets and by graft patency on 3 consecutive days after implantation at 1 month and 3 months. Forskolin significantly lowered early platelet sequestration onto the treated graft surface when compared with controls. Graft patency at 1 and 3 months was also significantly higher in the forskolin treated grafts.

The diagnosis of acute appendicitis still remains an enigma for the surgeon. The Mean Platelet volume is known to be a marker determined from megakaryocytes during platelet production, which is associated with platelet function and activation.The mean platelet volume (MPV) decreases in acute inflammatory conditions like acute appendicitis due to increased consumption and sequestration of platelets in the vascular segments of inflamed bowel. In our study of 213 patients, the MPV was determined and was found to be low ( < 7.6fL) in 176 patients ( 82.6%) out of which 175 patients were having features of acute appendicitis on histopathology. Therefore in a patient with a provisional diagnosis of acute appendicitis, a low MPV (

The discovery of citrate anticoagulant in the 1920s and the development of plastic packs for blood collection in the 1960s laid the groundwork for platelet transfusion therapy on a scale not previously possible. A major limitation, however, was the finding that platelet concentrates prepared from blood anticoagulated with citrate were unsuitable for transfusion because of platelet clumping. We found that this could be prevented by simply reducing the pH of platelet-rich plasma to about 6.5 prior to centrifugation. We used this approach to characterize platelet kinetics and sites of platelet sequestration in normal and pathologic states and to define the influence of variables such as anticoagulant and ABO incompatibility on post-transfusion platelet recovery. The "acidification" approach enabled much wider use of platelet transfusion therapy until alternative means of producing concentrates suitable for transfusion became available.

There is no agreement on the best technique of in situ flushing of livers prior to storage. In order to study this, porcine livers were stored in the University of Wisconsin (UW) solution for 18 h and then assessed using an isolated perfused porcine model. Livers flushed in situ with UW solution were compared to livers flushed with a non-preservation solution (Hartmann's solution). No statistically significant differences could be found in bile production (18.7 +/- 4.4 vs 17.9 +/- 3.8mL/1000 g per 2 h), aspartate amino-transferase (AST) levels in the perfusate after 2 h of isolated perfusion (687 +/- 101 vs 724 +/- 114 U/L), potassium levels in the perfusate after 2 h on the circuit (5.4 +/- 1.5 vs 5.5 +/- 2.3 mmol/L), weight gain (15.2 +/- 3.7 vs 17.1 +/- 4.0%) or platelet sequestration (41.6 +/- 11.7 vs 37.4 +/- 9.8%) between livers flushed with UW solution as opposed to those flushed with Hartmann's solution, respectively. Of overriding importance was the solution in which the liver was stored, reconfirming the superiority of UW solution over an extracellular solution for preservation. If extrapolated to the clinical situation, these findings would have substantial cost-saving implications.

Autologous transfusion is playing an important role in modern transfusion medicine. At San Martino hospital we use a combination of manual and mechanical techniques in order to improve autotransfusion procedures, control the hypertransfusion and avoid waste. Our autotransfusion program has determined a 55% reduction in the red cell concentrates used (from 42,000 in 1985 down to 19,400 in 1992). Proper training, cultural improvements and new applications on autotransfusion procedures will permit a better use of blood with less transfusion related complications, until a suitable substitute for blood will be available.

Rationale Thrombocytopenia is a platelet associated process that occurs in human and animals as result of i) decreased production; ii) increased utilization; iii) increased destruction coupled to the presence of antibodies, within a process know as immune-mediated thrombocytopenia (IMT); or iv) platelet sequestration. Thus, the differentiation of the origin of IMT and the development of reliable diagnostic approaches and methodologies are important in the clarification of IMT pathogenesis. Therefore, there is a growing need in the field for easy to perform assays for assessing platelet morphological characteristics paired with detection of platelet-bound IgG. Objectives This study is aimed to develop and characterize a single color flow cytometric assay for detection of platelet-bound IgG in horses, in combination with flow cytometric assessment of platelet morphological characteristics. Findings The FSC and SSC evaluation of the platelets obtained from the thrombocytopenic animals shows several distinctive features in comparison to the flow cytometric profile of platelets from healthy animals. The thrombocytopenic animals displayed i) increased number of platelets with high FSC and high SSC, ii) a significant number of those gigantic platelets had strong fluorescent signal (IgG bound), iii) very small platelets or platelet derived microparticles were found significantly enhanced in one of the thrombocytopenic horses, iv) significant numbers of these microplatelet/microparticles/platelet-fragments still carry very high fluorescence. Conclusions This study describes the development and characterization of an easy to perform, inexpensive, and noninvasive single color flow cytometric assay for detection of platelet-bound IgG, in combination with flow cytometric assessment of platelet morphological characteristics in horses.

Previous work in our department showed that after blood transfusion, the platelet count often falls to levels which are clinically significant. The probable site of platelet sequestration was identified as the spleen, and post-transfusion thrombocytopenia was prevented by blood filters which remove microaggregate debris from the donor blood [1, 2]. Since the duration of the thrombocytopenia has not been investigated, the purpose of the present study was to establish the rate of onset and duration of post-transfusion thrombocytopenia following packed red blood cell transfusions. In addition, the effect of spleen size, patients' diagnosis and post-transfusion history were examined. These observations provide interesting new data on the mechanisms involved in this phenomenon.

In five normal baboons, whole body 111In decreased slowly ( t sol 1 2 = 60 days ) after the end of platelet lifespan. There was slight elution of radioactivity from the liver and spleen, the important sites of platelet sequestration. A fraction of this eluted radioactivity accumulated in the bone marrow, but also in other tissues. This redistribution did not have a significant effect on the measurement of in vivo platelet kinetics. It did however, diminish the total weighted radiation dose, especially that due to contaminating 114mIn.

SummaryDuring body cooling, a progressive thrombocytopenia is observed, with platelet sequestration mainly in the liver. Platelets return progressively to the circulation during re warming. In this work the presence of platelet clumps is demonstrated by electron microscopy inside the hepatic sinusoids of dogs cooled to 20° C by immersion in iced water. Such clumps were not found either before cooling or after body rewarming. Similar platelet clumps in the hepatic microcirculation were found in two other groups of dogs cooled and rewarmed as before, but previously treated with the antiaggregants sulphinpyrazone or ticlopidine. Another group of dogs was cooled and rewarmed by intra-abdominal circulation of physiological saline respectively at 4° C and 40° C. In these animals a similar decrease of circulating platelets was observed. However, just after re warming was started, with the body temperature still at 22° C, sequestered platelets came back abruptly to circulation. We conclude that hepatic platelet sequestration induced by hypothermia appears mainly due to local haemodynamic conditions.

Significant soft-tissue trauma induces platelet activation, aggregation, and sequestration in the lungs. This pulmonary trapping is due either to the size of the platelet aggregates or to changes in the pulmonary microvasculature. To evaluate which one of these mechanisms is responsible for the trapping, we performed portacaval transposition in one group of pigs, making the liver the first receiving capillary bed for blood from the trauma sites in the lower extremities. One week after the operation, the platelets were labeled with indium oxine and reinfused, and the operated animals and a group of six control animals were subjected to standardized soft-tissue trauma to the lower extremities. Sequestration of platelets in the lungs and in the liver was registered dynamically before and for 90 minutes after the trauma. Soft-tissue trauma induced platelet sequestration in the liver in the operated group (p less than 0.01) and in the lungs in the control group (p less than 0.01). Trapping was paralleled by a decrease in the number of circulating platelets. This study has indicated that posttraumatic pulmonary platelet trapping is caused by platelet activation at the trauma sites and not by changes in the pulmonary microvasculature.

Platelet kinetics and functions were studied in dogs during extracorporeal circulation. A transient platelet sequestration in the liver occurs during the bypass. This reversible disappearance is accompanied by a loss of the ability of platelets to adhere or aggregate. The platelets which return to the circulation have normal functions and a normal life span. The irreversible damage is mainly due to the direct blood-gas interface. Impairment of lung function by platelet aggregates is discussed and the importance of an in vivo model to study the factors which affect the platelets, such as antiaggregating agents, is pointed out.

Besides decreased platelet production and an increased platelet sequestration in the spleen chronic DIC is thought to cause thrombocytopenia in chronic liver diseases. To investigate if this mechanism could play a role in patients with severe, but stable hepatic cirrhosis, we studied 32 pts. Twenty-eight of them had portal hypertension, 22 had bleeding episodes from oesophageal varices.

Optimal labelling conditions of human platelets with 111In-oxine were determined in vitro. Based on this optimized technique, platelet mean life span (MLS) and platelet sequestration site were comparatively evaluated in 79 patients with two labels, 51Cr (n = 26) and 111In (n = 53). Patients were subgrouped according to clinical criteria as autoimmune thrombocytopenic purpura (AITP) (group 1; n = 49), hypersplenism (2; n = 12), impaired thrombopoiesis (3; n = 3), unclassified thrombocytopenia (4; n = 6), and nonthrombocytopenic patients (5; n = 9). In patients with AITP and hypersplenism the mean values for the MLS determined either with 51Cr or with 111In were lowered but the difference was not statistically significant, neither for group 1 (18.6 h vs 17.3 h; P greater than 0.2) nor for group 2 (94.7 vs 122.3 h; P greater than 0.2). The correlation between MLS and platelet counts in patients with AITP was significant for both labels (P less than 0.001). The 15 min recovery tended to be higher with 111In in all groups, but the difference was significant (P less than 0.05) only for group 1. The sequestration sites were similar with both labels. We conclude that, contrary to previous reports, platelet survival studies yield similar results with both the 51Cr and 111In methods. Due to its distinct advantages 111In is the label of choice for investigation of platelet kinetics.

After injection of 51Cr-labelled platelets, dogs were cooled down to 20 °C and rewarmed to 36 °C. Radioactivity increased over the hepatic area during cooling, to decrease again during rewarming. It increased continuously during the observation period over the splenic area. The inverse symmetry of the curves representing the radioactivity measured over the liver and in the peripheral blood together with the fact that splenectomy did not alter significantly the thrombocytopenia observed, strongly suggests that in the dog the liver is the main organ responsible for platelet sequestration during hypothermia.

Summary. The clinical usefulness of external scanning data after infusion of 51Crlabelled platelets into patients with idiopathic thrombocytopenic purpura (ITP) is a matter of controversy. Observations have been made in 575 patients with ITP. Short-term (6 mth) results of splenectomy were assessed in 206 subjects, and longterm (1-3 yr) in 153. It appears that the site of sequestration is neither a direct function of the severity of the disease nor of the duration of the disease from the clinical onset. Diffuse sequestration, which cannot be taken as an indication for or against splenectomy, is frequently seen in recent and severe cases. Splenic sequestration is more often observed in young patients (72.5% under 30 yr of age) than in older subjects (36% over 30 yr of age). A good correlation was found between the site of sequestration and the shortand long-term results of splenectomy: success in more than 90% of cases with splenic sequestration but complete failure in 70% with hepatic sequestration. In any patient with ITP splenectomy should be undertaken only after a careful study of the platelet sequestration site.

A case of giant hemangioma with thrombocytopenia has been presented. Isotopic studies with Cr-51 tagged platelets indicated that the basic mechanism of thrombocytopenia in this patient involved platelet sequestration in the tumor. The platelet response in the peripheral blood following irradiation of the hemangioma gives additional evidence that the thrombocytopenia is related to pathological changes within the hemangioma.

The plasma beta-thromboglobulin (βTG) content was measured in 56 diabetic patients with known complications of this disease, including neuropathy, retinopathy, and ischemie skin lesions. Although two patients were found to have elevated levels beyond the normal range, there was no significant difference between the diabetic group as a whole and the group of 35 controls. The significance of these findings with regard to the proposed contribution of small-vessel platelet sequestration in the pathogenesis of late complications of diabetes mellitus is discussed.

Fourteen adults with idiopathic thrombocytopenic purpura suffered a relapse after treatment with steroids, vinca alkaloids, or intravenous gammaglobulin. Splenic sequestration of platelets labelled with 111In-oxine was assessed, and the patients then underwent splenectomy. During follow up of four to 47 months (mean 20.7) none of the patients required further treatment, including three of 14 who showed partial relapses. Splenic sequestration patterns did not predict relapses, but an unexpected finding was that patients who relapsed had significantly smaller spleens. It is concluded that splenectomy is beneficial in most adult patients with idiopathic thrombocytopenic purpura and that radiological techniques to measure the size of the spleen may be useful in predicting which patients may relapse.

The3H-thymidine labeling index (3H-TdR-index), the concentration/0.1 mm2 tissue area and the diameters of splenic megakaryocytes were determined in rats after 2/3 partial hepatectomy, sham operation or intravenous antigen injection (sheep erythrocytes). During the first 36 hours after partial hepatectomy a slight, though not significant decrease of the3H-TdR-index was noticed. The maximal values were obtained at the third postoperative day. The changes in the megakaryocyte numbers showed large variations and only at the eighth day a significant increase was visible. No makromegakaryocytes were observed and cell diameters did not increase. However, at days 4, 6 and seven a significant decrease of megakaryocyte sizes developed. After sham operation an immediate rise of the labeling index of splenic megakaryocytes with a maximum 36 hours postoperatively occured, whereas cell numbers and diameters changed only slightly. The injection of antigens had no measurable effect on megakaryocytopoiesis. As after other kinds of tissue damages megakaryocyte maturation time was reduced in sham operated and partial hepatectomized animals thus obviously compensating an increased peripheral platelet demand (wound repair, blood loss). At what level and to what extent the megakaryocyte renewal system in the spleen was affected by the partial hepatectomy as well as the nature of the observed initial delay in radioactive labeling cannot be concluded from this investigation with certainty. But it may well be correlated with a temporally reduction of the platelet sequestration capacity of the liver after partial hepatectomy. The rate of peripheral destruction of platelets may influence platelet production and megakaryocytopoiesis independantly of the platelet count.

A thrombocytopenic patient with pulmonary hemangiolymphangiectasia proven by biopsy, was studied for platelet sequestration with In-111-labeled autologous platelets. The 24-hour scan showed diffuse increased uptake throughout both lung fields, indicating platelet sequestration by the diffuse pulmonary hemangiolymphangiectasia.

Using a sheep model, platelet sequestration in lungs, liver, kidney, spleen, and brain was studied after the injection of Indium-111-oxine-labeled platelets and E. coli lipopolysaccharide. Immediately following endotoxin-induced shock, platelet sequestration was observed in lungs, liver, and kidney with corresponding decrease in measured Indium-111-oxine platelets in spleen and circulating blood. There was also a decrease in platelet counts as measured in a phase contrast microscope. The early platelet sequestration in lung, liver, and kidney was followed by platelet disaggregation and another phase of platelet sequestration which continued until the death of the animal. No platelet sequestration was observed in the brain.

51Cr-platelet kinetics study was performed in 197 patients with chronic ITP after corticosteroid therapy had failed to induce a long lasting remission. The incidence of splenic, spleno-hepatic, hepatic and diffuse platelet sequestration site was 58 %, 17 %, 6% and 19 %, respectively. Splenic and spleno-hepatic sequestration sites were more frequent in patients less than 30 years old and in patients with a platelet count lower than 50 times 109/1. Ill patients were splenectomized shortly after the study. Normalization of the platelet count was obtained more frequently in patients with splenic and spleno-hepatic sequestration than in the others. Labelled platelet sequestration site was the best predictor of the outcome of splenectomy. Platelet kinetics is a non-invasive investigation that should be performed early after the diagnosis of chronic ITP in all patients eligible for splenectomy.

The mean fall in the platelet count following 23 routine transfusions of 3-5 units packed cells for anaemia was 32.5%. This was significantly reduced to 12.5% in 15 similar transfusions through a 40 microns microaggregate filter (P less than 0.01) and to 4.6% following five transfusions through a polyester fibre filter (P less than 0.005). In 10 transfusions with frozen or polyester fibre filtered, washed red cells, the decrease in platelet count was 4.2% (P less than 0.001). A study of 111In-oxine labelled autologous platelets in nine patients indicated that the fall in platelet count was due to increased splenic sequestration. Since thrombocytopenia following routine transfusion is reduced by procedures which filter the packed cells, the decrease in platelets is probably caused by their adherence to infused microaggregate debris causing their premature removal from the circulation. Patients with preexisting thrombocytopenia who receive red cell transfusions for anaemia, should therefore receive blood products depleted of microaggregate debris in order to avoid exacerbation of thrombocytopenia and haemorrhagic complications.

Summary. Platelet-associated IgG (PAIgG), platelet mean life span (MLS), and platelet sequestration sites were studied in 69 patients with immune (ITP) and presumed nonimmune thrombocytopenias (NTP). A shortened MLS was associated with elevated PAIgG (N=46), and with normal PAIgG (N=15), Four patients had a normal MLS, but elevated PAIgG, four patients were normal for both parameters. The highest PAIgG values occurred in ITP patients with a very short MLS. Nine NTP patients had also elevated PAIgG, but a normal or slightly shortened MLS. There was a significant double log correlation between PAIgG and MLS for ITP, but not for NTP patients. Judged from the coefficient of determination, only 10% of PAIgG were directly related to a shortened MLS. 70% of patients (N= 63) had exclusively splenic and 30% hepatosplenic sequestration. PAIgG was elevated in 29/44 patients with splenic (66%) and in 16/19 patients with hepatosplenic sequestration (84%). In ITP, PAIgG-positive cases were observed in 69% of splenic v82% of hepatosplenic sequestration, while in NTP the corresponding figures were 6/11 and 2/2. No significant correlation between PAIgG and either sequestration type was demonstrable. We conclude that in immunologically mediated thrombocytopenia only a small portion of PAIgG accounts for a decreased MLS, and that the concentration of PAIgG per se does not determine the platelet sequestration type.

We herein report the successful use of epsilon-aminocaproic acid to reverse the thrombocytopenia and coagulopathy in a girl with the Klippel-Trenaunay syndrome. The efficacy of the treatment was associated with thrombosis and obliteration of the abnormal vascular channels

Excerpt The usefulness of51Cr platelet survival and sequestration studies in predicting response to splenectomy in idiopathic thrombocytopenic purpura and other autoimmune thrombocytopenias remains...