The threshold for prophylactic platelet transfusions in adults with acute myeloid leukemia. Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto

A rapid and accurate closed-tube immunoassay for platelets on an automated hematology analyzer

Accurate and precise platelet counts are important for patients with severe thrombocytopenia or who are receiving chemotherapy. We developed a novel flow cytometric analysis of platelets that may be particularly valuable for assessing the necessity for platelet transfusions. This ImmunoPlt (CD61) assay is based in part on CD61 monoclonal antibody labeling and has been automated and implemented on the CELL-DYN 4000 hematology analyzer. It is well suited for thrombocytopenic specimens, since it reduces interference by nonplatelet particles. It takes less than 5 minutes from closed-tube aspiration to report. Data for more than 350 thrombocytopenic specimens demonstrate that the ImmunoPlt (CD61) assay is more accurate than the optical scatter or the impedance count for specimens with platelet counts between 1 and 60 x 10(3)/microL (1 and 60 x 10(9)/L). The ImmunoPlt (CD61) assay is more precise than the optical scatter or the impedance count for specimens with platelet counts between 1 and 50 x 10(3)/microL (1 and 50 x 10(9)/L).

Current and future trends in transfusion therapy

The increase in intensive treatment for cancer has impacted blood product transfusion practices. Transfusion guidelines are primarily institution specific, but the general concepts and theories are universal. Blood product screening has decreased the risk of transfusion-acquired infections; however, the risk is not obsolete. This article reviews current approaches to platelet, white blood cell, and red blood cell transfusions, as well as risks associated with these therapies (e.g., infection and transfusion-associated graft-versus-host disease). Pertinent laboratory studies, patient assessment, blood product administration, and patient education is discussed. The current approaches to platelet, white blood cell, and red blood cell transfusions are constantly changed and evaluated. Pediatric oncology nurses must stay up to date with these changes to provide optimal patient care.

Management of patients with chronic, refractory idiopathic thrombocytopenic purpura

Chronic refractory idiopathic thrombocytopenic purpura (ITP) is defined as ITP with persistent thrombocytopenia despite conventional initial management with prednisone and splenectomy. Rare in children, It may occur in as many as one third of adults with ITP. The goal of treatment is not cure of the ITP, but only to achieve a safe platelet count, which is arbitrarily assumed to be greater than 30,000 to 50,000/microL. The risk for major bleeding seems great only when the platelet count is less than 10,000/microL. Treatment of patients with moderate thrombocytopenia and no clinically important bleeding symptoms should be avoided. There is no accepted algorithm for management of patients with chronic refractory ITP. Observation without specific treatment must be considered a cornerstone of management. Combination regimens of Immunosuppressive agents may be required for patients with severe and symptomatic thrombocytopenia. Additional supportive care measures are also important.

A comparison of prestorage WBC-reduced whole-blood-derived platelets and bedside-filtered whole-blood-derived platelets in autologous progenitor cell transplant

BACKGROUND

Prestorage WBC-reduced platelet concentrates (PCs) can be manufactured from platelet-rich plasma (PRP) by in-line filtration of PRP. There are few published data on the clinical use of these products, as compared to bedside-filtered pools of standard PCs (S-PCs) manufactured from PRP.

STUDY DESIGN AND METHODS

A prospective, randomized trial was conducted in autologous progenitor cell transplant patients requiring platelet transfusions with each patient as his or her own control who was given a pool of 5 units of WBC-reduced PCs and a pool of 6 units of S-PCs within a 3-hour period. The pools were characterized before transfusion for platelet and WBC content, P-selectin expression, and IL-8. The patients were monitored with platelet counts and vital signs and observed for reactions. Data were analyzed using Mann-Whitney U tests.

RESULTS

Thirty-three transfusions were administered to 13 patients. Median platelet content in the WBC-reduced PC pools was lower than that in the S-PC pools (3.3 vs. 4.0 x 10(11), p<0.01). Median WBC content was 4 to 5 log less in the WBC-reduced PC pools (2.5 x 10(4) vs. 4.6 x 10(8), p<0.01). Median IL-8 levels (pg/mL) were lower in the WBC-reduced PC pools (2 vs. 36, p<0.01). No differences were observed in CCI, but the median absolute increase after transfusion of the S-PC pools was higher (25 vs. 19 x 10(9)/L, p<0.01), which reflected the larger size of the S-PC pools. No overall differences in vital signs were recorded. Two reactions were observed, both in temporal association with the transfusion of pools of S-PCs.

CONCLUSIONS

A pool consisting of 5 units of WBC-reduced PCs gave a median platelet increment of 19 x 10(9) per L in these thrombocytopenic patients and has a median WBC content 1 to 2 log below the accepted threshold for primary alloimmunization or CMV transmission.

Apheresis platelets: emerging issues related to donor platelet count, apheresis platelet yield, and platelet transfusion dose

Emerging issues in stimulating apheresis platelet donors with platelet growth factors, the relative costs of apheresis and random donor platelet concentrates, optimal platelet transfusion dose, and leucoreduction of platelet products have caused renewed debate regarding apheresis products vs. random, pooled concentrates. The future role of apheresis products in platelet transfusion therapy will in large part be determined by costs, which are increasingly recognized to be influenced by donor platelet count, apheresis yield, and platelet transfusion dose.

Paroxysmal nocturnal hemoglobinuria and the risk of venous thrombosis: review and recommendations for management of the pregnant and nonpregnant patient

BACKGROUND

Paroxysmal nocturnal hemoglobinuria is a rare, clonal primitive hematopoietic cell disorder, often affecting middle-aged adults, including women of reproductive age. Major morbidity and mortality with this disease are often ascribed to the development of venous thromboembolism. We reviewed the current literature on the risk of venous thrombosis among nonpregnant and pregnant patients, and generated recommendations for the prevention of venous thromboembolism, as well as duration of treatment for affected patients who develop thrombotic disease.

METHODS

We searched Medline for papers published between January 1966 and April 1999. We also requested relevant unpublished data from speakers who attended a recent international workshop of paroxysmal nocturnal hemoglobinuria. References from all primary data and review publications were also examined. Only English language publications were included. Event rates for venous thromboembolism and death were pooled using a random effect technique. Reports of paroxysmal nocturnal hemoglobinuria during pregnancy were summarized using descriptive statistics only.

RESULTS

Thirteen retrospective studies of paroxysmal nocturnal hemoglobinuria in nonpregnant individuals were found. The rates of venous thrombosis varied considerably, but were reported to affect 14.4% of all individuals [95% confidence interval (CI) 7.6-25.5]. Among patients from western nations, venous thromboembolism seemed to develop at a higher rate (30.3%, 95% CI 26. 1-34.9). The majority of venous thromboembolic events were intra-abdominal, principally within the hepatic and mesenteric veins. The likely cause of death among patients with paroxysmal nocturnal hemoglobinuria was described in nine studies: 22.2% of fatalities were due to venous thrombosis (95% CI 11.8-38.0), more commonly in western countries (event rate 37.2%, 95% CI 21.6-56.0). Another 20 published reports described the outcome of 33 pregnant women with paroxysmal nocturnal hemoglobinuria. Two women developed venous thromboembolism during pregnancy and another 2 during the postpartum state for a combined event rate of 12.1% (95% CI 3.4-25.2), three of which resulted in death. The all-cause mortality rate was 20.8% (95% CI 7.3-39.0). Both anemia (event rate 72.7%, 95% CI 56.5-86.3), and thrombocytopenia (event rate 27.3%, 95% CI 13.7-43.5) were common, often necessitating red cell or platelet transfusions. Almost half of all infants (54.8%, 95% CI 36.1-72.7) were delivered preterm, and had a mean live birth weight of 2,800 g. Three of 34 reported births ended in death (perinatal mortality rate 8.8%, 95% C 1.9-23.7).

CONCLUSION

In accordance with the apparently high rate of venous thrombosis among pregnant and nonpregnant individuals with paroxysmal nocturnal hemoglobinuria, especially for fatal thrombosis, we developed practical recommendations for the prevention and treatment of venous thromboembolic disease in these groups.

A double-blind, placebo-controlled trial of pegylated recombinant human megakaryocyte growth and development factor as an adjunct to induction and consolidation therapy for patients with acute myeloid leukemia

Newly diagnosed patients with acute myeloid leukemia (AML) were randomized to receive either 2.5 or 5 μg/kg/day of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) or a placebo administered subcutaneously after completion of chemotherapy. The study evaluated the toxicity of PEG-rHuMGDF and any effect on the duration of thrombocytopenia. Each of 35 patients under 60 years of age received the following therapy: 45 mg/m2 daunorubicin on days 1-3, 100 mg/m2cytarabine (ARA-C) for 7 days, and 2 gm/m2 high-dose ARA-C (HIDAC) for 6 doses on days 8-10. The 22 patients 60 years or older received standard daunorubicin and ARA-C without HIDAC. PEG-rHuMGDF was well tolerated, and no specific toxicities could be attributed to its use. There was no difference in the time to achieve a platelet count of at least 20 × 109/L among the 3 groups (median 28-30 days for patients less than 60 years old and 21-23 days for patients 60 years or older). Patients receiving PEG-rHuMGDF achieved higher platelet counts after remission. However there was no significant difference in the number of days on which platelet transfusions were administered among the 3 groups. The complete remission rate was 71% for patients less than 60 years and 64% for those 60 years or older, with no significant difference among the 3 groups. Postremission consolidation chemotherapy with either placebo or PEG-rHuMGDF was given to 28 patients beginning the day after completion of chemotherapy. There was no apparent difference in the time that was necessary to reach a platelet count of at least 20 or 50 × 109/L or more platelets or in the number of platelet transfusions received. In summary, PEG-rHuMGDF was well tolerated by patients receiving induction and consolidation therapy for AML; however, there was no effect on the duration of severe thrombocytopenia or the platelet transfusion requirement.

A double-blind, placebo-controlled trial of pegylated recombinant human megakaryocyte growth and development factor as an adjunct to induction and consolidation therapy for patients with acute myeloid leukemia

Newly diagnosed patients with acute myeloid leukemia (AML) were randomized to receive either 2.5 or 5 μg/kg/day of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) or a placebo administered subcutaneously after completion of chemotherapy. The study evaluated the toxicity of PEG-rHuMGDF and any effect on the duration of thrombocytopenia. Each of 35 patients under 60 years of age received the following therapy: 45 mg/m2 daunorubicin on days 1-3, 100 mg/m2cytarabine (ARA-C) for 7 days, and 2 gm/m2 high-dose ARA-C (HIDAC) for 6 doses on days 8-10. The 22 patients 60 years or older received standard daunorubicin and ARA-C without HIDAC. PEG-rHuMGDF was well tolerated, and no specific toxicities could be attributed to its use. There was no difference in the time to achieve a platelet count of at least 20 × 109/L among the 3 groups (median 28-30 days for patients less than 60 years old and 21-23 days for patients 60 years or older). Patients receiving PEG-rHuMGDF achieved higher platelet counts after remission. However there was no significant difference in the number of days on which platelet transfusions were administered among the 3 groups. The complete remission rate was 71% for patients less than 60 years and 64% for those 60 years or older, with no significant difference among the 3 groups. Postremission consolidation chemotherapy with either placebo or PEG-rHuMGDF was given to 28 patients beginning the day after completion of chemotherapy. There was no apparent difference in the time that was necessary to reach a platelet count of at least 20 or 50 × 109/L or more platelets or in the number of platelet transfusions received. In summary, PEG-rHuMGDF was well tolerated by patients receiving induction and consolidation therapy for AML; however, there was no effect on the duration of severe thrombocytopenia or the platelet transfusion requirement.

Current issues with platelet transfusion in patients with cancer

For the past 30 years, platelet transfusions have been used in the treatment of thrombocytopenia caused by decreased production, inadequate function, or increased destruction of platelets. The number of platelet transfusions has increased more than transfusions of other blood components, shifting from whole blood use for the platelet source to plateletpheresis. Hematology/oncology patients are among the largest group receiving platelet transfusions, primarily because the more aggressive chemotherapies produce more acute and prolonged thrombocytopenia. While platelet transfusions often rescue patients with very low platelet levels, they are associated with the risk of viral and bacterial infections, as well as alloimmunization. Platelet donor recruitment can also be difficult, and platelet transfusion can be very expensive depending on the source of platelets. As a result, prophylactic transfusions are less likely to be administered at higher platelet counts, reducing platelet use and cost of platelet transfusions. However, cancer patients receiving intensive chemotherapy or myeloablative regimens require multiple platelet transfusions. For these patients, alternate strategies are needed so that platelet transfusions can be significantly reduced or eliminated.

Hematologic management of gastrointestinal bleeding

The hematologic management of gastrointestinal (GI) bleeding requires evaluation of the underlying cause of bleeding, associated diseases that can exacerbate the bleeding, and identification of related and unrelated coagulation abnormalities. Erythrocyte transfusions are given to increase oxygen carrying capacity; however, there is limited information on the level of anemia that places a patient at increased risk of adverse events after a GI bleed and when patients should receive erythrocyte transfusion. Isolated thrombocytopenia is uncommon in patients with GI bleeding, and there is little evidence documenting the degree of thrombocytopenia associated with an increased risk of bleeding. Platelets are often administered when the count is 50,000 per cu/mL in a bleeding patient. The coagulopathy of liver disease is the most common abnormality seen in the setting of GI bleeding. Fresh-frozen plasma (FFP) should be given in a dose equivalent to the underlying abnormality and the common practice of administering 2 units of FFP is often insufficient in a bleeding patient.

Immunoplatelet counting: a proposed new reference procedure

Given the high degree of interoperator error and poor precision of manual platelet counting, it has recently been proposed that an immunoplatelet counting method could become the new reference procedure. Platelets are identified immunologically with a suitable monoclonal antibody, and the platelet count is derived from the ratio of fluorescent platelet events to collected red blood cell (RBC) events that are also counted by a reliable and calibrated standard impedance counter (RBC ratio). In this study, we have set up a rapid and simple method for immunoplatelet counting and simultaneously compared the RBC ratio with the bead ratio derived from two different preparations of commercial calibration beads (Trucount and FlowCount beads). Comparison of the level of imprecision of the RBC ratio with either the manual count or bead ratios revealed a superior coefficient of variation of < 5% even in samples with a platelet count < 20 x 10(9)/l. The RBC ratio correlated extremely well with the existing manual phase reference method (r2 = 0.93) and especially well with three different commercial impedance counters and a dual-angle optical counter (r2 = 0.98-0.99). However, at < 100 x 10(9)/l, the correlation of the RBC ratio with the dual-angle optical count (ADVIA 120) (r2 = 0.96) was superior to all impedance counters. This suggests that automated optical counting methods may be more accurate at determining platelet counts in thrombocytopenic samples. As the RBC ratio is rapid, cheap and relatively easy to perform, we propose that this method could replace the manual count as a new international reference method.

A Randomized, Double-Blind, Placebo-Controlled Study With Pegylated Recombinant Human Megakaryocyte Growth and Development Factor (PEG-rHuMGDF) as an Adjunct to Chemotherapy for Adults With De Novo Acute Myeloid Leukemia

To determine the safety, biologic, and clinical benefits of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF; Amgen, Thousand Oaks, CA) after myelosuppressive chemotherapy in acute myeloid leukemia (AML), 108 adult patients with de novo AML were randomized to receive either PEG-rHuMGDF (2.5 μg/kg/d or 5 μg/kg/d) for up to 21 doses (group A), a single dose of 2.5 μg/kg PEG-rHuMGDF, 7 daily doses of 2.5 μg/kg PEG-rHuMGDF (group B), or placebo. The greatest biologic activity was seen in group A with a median peak platelet count of 1,084 × 109/L, occurring at a median 9 days after the last dose of study drug, compared with 517 × 109/L and 390 × 109/L in group B and placebo group, respectively. Thrombocytosis (platelets &gt;1,000 × 109/L) was seen at rates of 52%, 8%, and 9% in groups A, B, and placebo, respectively, but were not associated with any adverse event. There was no effect on median time to transfusion independent platelet recovery (≥20 × 109/L). The median time to neutrophil recovery (≥500/μL) and red blood cell transfusion requirements were similar in all groups, and there was no apparent stimulation of leukemia. PEG-rHuMGDF was biologically active and well tolerated. Further investigation of dose and scheduling is required, specifically earlier dosing before and during chemotherapy.

A Randomized, Double-Blind, Placebo-Controlled Study With Pegylated Recombinant Human Megakaryocyte Growth and Development Factor (PEG-rHuMGDF) as an Adjunct to Chemotherapy for Adults With De Novo Acute Myeloid Leukemia

To determine the safety, biologic, and clinical benefits of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF; Amgen, Thousand Oaks, CA) after myelosuppressive chemotherapy in acute myeloid leukemia (AML), 108 adult patients with de novo AML were randomized to receive either PEG-rHuMGDF (2.5 μg/kg/d or 5 μg/kg/d) for up to 21 doses (group A), a single dose of 2.5 μg/kg PEG-rHuMGDF, 7 daily doses of 2.5 μg/kg PEG-rHuMGDF (group B), or placebo. The greatest biologic activity was seen in group A with a median peak platelet count of 1,084 × 109/L, occurring at a median 9 days after the last dose of study drug, compared with 517 × 109/L and 390 × 109/L in group B and placebo group, respectively. Thrombocytosis (platelets >1,000 × 109/L) was seen at rates of 52%, 8%, and 9% in groups A, B, and placebo, respectively, but were not associated with any adverse event. There was no effect on median time to transfusion independent platelet recovery (≥20 × 109/L). The median time to neutrophil recovery (≥500/μL) and red blood cell transfusion requirements were similar in all groups, and there was no apparent stimulation of leukemia. PEG-rHuMGDF was biologically active and well tolerated. Further investigation of dose and scheduling is required, specifically earlier dosing before and during chemotherapy.

Optimal dosing and triggers for prophylactic use of platelet transfusions

Despite the reliance on platelet transfusion support in patients receiving myeloablative therapy, controversies surround platelet transfusion practices. These include the appropriate platelet dose and the threshold at which prophylactic platelet transfusions will be most effective. These issues bear directly on patient outcome (donor exposure and bleeding complications), cost effectiveness of transfusion, and maintenance of adequate platelet inventories. This review examines the recent studies that have taken on the task of resolving these questions in order to provide optimal platelet transfusion guidelines. Studies now have convincingly demonstrated that a 10,000/microL threshold for prophylactic platelet transfusion is safe and effective in uncomplicated thrombocytopenic patients. Although platelet dosages vary, in general, smaller doses are both effective and inventory-sparing in the more complicated inpatient setting, while larger platelet doses allow for an increased transfusion interval for chronic outpatient support.

Platelets: preparations, transfusion, modifications, and substitutes

OBJECTIVE

To summarize current knowledge and recent progress pertaining to platelet concentrate preparations, modifications, and future prospects for platelet substitutes.

METHODS

Current publications identified through a search of an electronic literature database were evaluated and reviewed. Relevant data were abstracted into this article. Abstractions of the data were made depending on their relevance. This review starts with standard methods of platelet preparation and goes on to describe different modifications intended to optimize the product and increase its safety. The article concludes with a discussion of the use of hematopoietic growth factors and novel kinds of platelet components for future use.

CONCLUSIONS

Many modifications in the preparation of platelet transfusions have occurred in recent years. Platelets prepared by standard techniques contain significant numbers of donor leukocytes, which are responsible for several adverse effects. Awareness of this problem has lead to the development of effective means for their removal. Several methods to reduce the risk of viral and bacterial transmission through platelet transfusions are emerging. New technologies in the use of platelet substitutes have attempted to prolong the platelet storage potential and prevent the development of recipient alloimmunization. As the biological activities of growth factors become better understood, the clinical applications of novel recombinant products may redefine the concept of future platelet transfusions. It is important that research continues into the optimal methods for the preparation and use of platelet transfusions to provide maximal clinical benefits with minimal risk of complications.

Outcomes in transfusion

Outcomes data in medicine can be limited by subjective methodologic issues such as poor selection of end points and use of nonvalidated systems for quality adjustment. Blood transfusion analyses are further complicated by the fact that transfusion seldom is primary therapy but is usually supportive or adjunctive. Thus, much of the outcome data in transfusion medicine are either unavailable or in one of two areas. The first area is prevention of bad sequelae of various cytopenias or factor deficiencies. The second is decreasing adverse effects of transfusion itself. A different useful area for outcome and root cause approaches in individual institutions is examining preanalytical and postanalytical processes of their own. Examples are sample labeling accuracy, quality and timeliness of blood suppliers, internal delivery processes and times, and product wastage. Use review can be changed to real time from retrospective time. By reducing complaints about service to objective data, realistic change can be made in internal and external processes.

How to improve transfusion medicine. A treating physician's perspective

As transfusion medicine becomes more complex, cooperative strategies are gaining increasing importance in relaying information to the treating physician and in incorporating the treating physician into the education and quality control processes. The broad domain of transfusion medicine is illustrated by the variety of disciplines involved in defining the use of products such as fresh frozen plasma and the newly released solvent-detergent-treated plasma, fibrin glue and highly purified fibrin sealant, and leukoreduced and irradiated blood products. Cooperative efforts among physicians and other personnel of multiple disciplines are essential to ensure appropriate use and continuous evaluation of blood products.

Risks, costs, and alternatives to platelet transfusions

The use of platelet transfusions has increased greatly in the past decade and is likely to continue to escalate because of the risks of thrombocytopenia in patients receiving dose-intensive cancer chemotherapy, the increased use of hematopoietic progenitor cell transplantation, and the prevalence of human immunodeficiency virus infection. Despite marked advances in procedures for ensuring the safety of platelets, including intensive donor screening, infectious disease marker testing, and increased use of leukodepletion techniques, platelet transfusions carry a significant risk for immunologic disorders and transmission of bacterial, viral, and perhaps other diseases and can entail a very high cost. In addition, thrombocytopenia has the potential to interfere with delivery of chemotherapy on schedule and at the planned doses, thus potentially compromising treatment outcome. The limitations of platelet transfusions have prompted the development of agents with the potential to stimulate platelet production and thus reduce or eliminate the need for transfusions. Two such agents, interleukin-11 (IL-11) and thrombopoietin (TPO), have demonstrated promise in clinical trials. In November, 1997, IL-11 received FDA approval for the prevention of severe thrombocytopenia in high risk patients receiving myelosuppressive chemotherapy. Thrombopoietic growth factors have the potential to greatly simplify and increase the safety of transfusion medicine.

Recombinant Human Thrombopoietin in Combination With Granulocyte Colony-Stimulating Factor Enhances Mobilization of Peripheral Blood Progenitor Cells, Increases Peripheral Blood Platelet Concentration, and Accelerates Hematopoietic Recovery Following High-Dose Chemotherapy

Lineage-specific growth factors mobilize peripheral blood progenitor cells (PBPC) and accelerate hematopoietic recovery after high-dose chemotherapy. Recombinant human thrombopoietin (rhTPO) may further increase the progenitor-cell content and regenerating potential of PBPC products. We evaluated the safety and activity of rhTPO as a PBPC mobilizer in combination with granulocyte colony-stimulating factor (G-CSF) in 29 breast cancer patients treated with high-dose chemotherapy followed by PBPC reinfusion. Initially, patients received escalating single doses of rhTPO intravenously (IV) at 0.6, 1.2, or 2.4 μg/kg, on day 1. Subsequent patients received rhTPO 0.6 or 0.3 μg/kg on days −3, −1, and 1, or 0.6 μg/kg on days −1 and 1. G-CSF, 5 μg/kg IV or subcutaneously (SC) twice daily, was started on day 3 and continued through aphereses. Twenty comparable, concurrently and identically treated patients (who were eligible and would have been treated on protocol but for the lack of study opening) mobilized with G-CSF alone served as comparisons. CD34+ cell yields were substantially higher with the first apheresis following rhTPO and G-CSF versus G-CSF alone: 4.1 × 106/kg (range, 1.3 to 17.6) versus 0.8 × 106/ kg (range, 0.3 to 4.2), P = .0003. The targeted minimum yield of 3 × 106CD34+ cells/kg was procured following a single apheresis procedure in 61% of the rhTPO and G-CSF–mobilized group versus 10% of G-CSF–mobilized patients (P = .001). In rhTPO and G-CSF mobilized patients, granulocyte (day 8 v 9, P= .0001) and platelet recovery (day 9 v 10, P= .07) were accelerated, and fewer erythrocyte (3 v 4,P = .02) and platelet (4 v 5, P = .02) transfusions were needed compared with G-CSF–mobilized patients. Peripheral blood platelet counts, following rhTPO and G-CSF, were increased by greater than 100% and the platelet content of PBPC products by 60% to 110% on the first and second days of aphereses (P < .0001) with the greatest effect seen with repeated dosing of rhTPO at 0.6 μg/kg. rhTPO is safe and well tolerated as a mobilizing agent before PBPC collection. Mobilization with rhTPO and G-CSF, in comparison to a comparable, nonrandomized G-CSF–mobilized group of patients, decreases the number of apheresis procedures required, may accelerate hematopoietic recovery, and may reduce the number of transfusions required following high-dose chemotherapy for breast cancer.

A Restrictive Platelet Transfusion Policy Allowing Long-Term Support of Outpatients With Severe Aplastic Anemia

The threshold for prophylactic platelet transfusions in patients with hypoplastic thrombopenia generally recommended in the standard literature is 20,000 platelets/μL. A more restrictive transfusion policy may be indicated in patients with chronic severe aplastic anemia (SAA) in need of long-term platelet support. We evaluated the feasibility and safety of a policy with low thresholds for prophylactic transfusions (≤5,000 platelets/μL in stable patients; 6,000 to 10,000 platelets/μL in cases with fever and/or hemorrhagic signs) combined with progressive lengthening of transfusion intervals (up to at least 7 days irrespective of the interim course of platelet counts). The study was based on a retrospective analysis of a total of 18,706 patient days with platelet counts ≤10,000/μL in patients with chronic SAA treated (for more than 3 months) on an outpatient basis. Altogether, 1,135 platelet transfusions were given, 88% at counts ≤10,000/μL and 57% at counts ≤5,000/μL. The mean transfusion interval was 10 days. During the period of observation, three major nonlethal bleeding complications occurred, which could be well controlled. We conclude that the restrictive policy with low transfusion thresholds and prolonged transfusion intervals proved feasible and safe in chronic SAA patients.

Pediatric transfusion therapy: practical considerations

Over the past decade, safety of blood has increased tremendously because of better donor screening as well as testing of the units for transmissible diseases. Component therapy has allowed more effective and economic use of blood. Whole blood is rarely used; instead, packed red cells, platelets, and fresh frozen plasma (FFP) are the most common components used. These products are further refined using irradiation and microaggregate filters and in the case of FFP, viral inactivation. Irradiation prevents transfusion-associated graft versus host disease, whereas microaggregate filters remove leukocytes, decreasing the rates of alloimmunization, febrile nonhemolytic (FNH) reactions, and cytomegalovirus (CMV) transmission. Autologous donation in older children probably provides the safest blood as far as transmissible diseases are concerned. More families request a directed donation and solicit physician help in deciding as well as making arrangements for autologous and/or directed donations. Transfusions of blood and blood components in children are often challenging and require a knowledge of physiologic changes in hemoglobin and blood volumes during different ages. The unique needs of neonates, immunocompromised patients, and patients with congenital hemolytic anemia (sickle cell, thalassemia) mandate that the pediatrician have an appropriate knowledge of transfusion volumes and choice of blood product as well as indications for transfusion.

A Restrictive Platelet Transfusion Policy Allowing Long-Term Support of Outpatients With Severe Aplastic Anemia

The threshold for prophylactic platelet transfusions in patients with hypoplastic thrombopenia generally recommended in the standard literature is 20,000 platelets/μL. A more restrictive transfusion policy may be indicated in patients with chronic severe aplastic anemia (SAA) in need of long-term platelet support. We evaluated the feasibility and safety of a policy with low thresholds for prophylactic transfusions (≤5,000 platelets/μL in stable patients; 6,000 to 10,000 platelets/μL in cases with fever and/or hemorrhagic signs) combined with progressive lengthening of transfusion intervals (up to at least 7 days irrespective of the interim course of platelet counts). The study was based on a retrospective analysis of a total of 18,706 patient days with platelet counts ≤10,000/μL in patients with chronic SAA treated (for more than 3 months) on an outpatient basis. Altogether, 1,135 platelet transfusions were given, 88% at counts ≤10,000/μL and 57% at counts ≤5,000/μL. The mean transfusion interval was 10 days. During the period of observation, three major nonlethal bleeding complications occurred, which could be well controlled. We conclude that the restrictive policy with low transfusion thresholds and prolonged transfusion intervals proved feasible and safe in chronic SAA patients.

Recombinant Human Thrombopoietin in Combination With Granulocyte Colony-Stimulating Factor Enhances Mobilization of Peripheral Blood Progenitor Cells, Increases Peripheral Blood Platelet Concentration, and Accelerates Hematopoietic Recovery Following High-Dose Chemotherapy

Lineage-specific growth factors mobilize peripheral blood progenitor cells (PBPC) and accelerate hematopoietic recovery after high-dose chemotherapy. Recombinant human thrombopoietin (rhTPO) may further increase the progenitor-cell content and regenerating potential of PBPC products. We evaluated the safety and activity of rhTPO as a PBPC mobilizer in combination with granulocyte colony-stimulating factor (G-CSF) in 29 breast cancer patients treated with high-dose chemotherapy followed by PBPC reinfusion. Initially, patients received escalating single doses of rhTPO intravenously (IV) at 0.6, 1.2, or 2.4 μg/kg, on day 1. Subsequent patients received rhTPO 0.6 or 0.3 μg/kg on days −3, −1, and 1, or 0.6 μg/kg on days −1 and 1. G-CSF, 5 μg/kg IV or subcutaneously (SC) twice daily, was started on day 3 and continued through aphereses. Twenty comparable, concurrently and identically treated patients (who were eligible and would have been treated on protocol but for the lack of study opening) mobilized with G-CSF alone served as comparisons. CD34+ cell yields were substantially higher with the first apheresis following rhTPO and G-CSF versus G-CSF alone: 4.1 × 106/kg (range, 1.3 to 17.6) versus 0.8 × 106/ kg (range, 0.3 to 4.2), P = .0003. The targeted minimum yield of 3 × 106CD34+ cells/kg was procured following a single apheresis procedure in 61% of the rhTPO and G-CSF–mobilized group versus 10% of G-CSF–mobilized patients (P = .001). In rhTPO and G-CSF mobilized patients, granulocyte (day 8 v 9, P= .0001) and platelet recovery (day 9 v 10, P= .07) were accelerated, and fewer erythrocyte (3 v 4,P = .02) and platelet (4 v 5, P = .02) transfusions were needed compared with G-CSF–mobilized patients. Peripheral blood platelet counts, following rhTPO and G-CSF, were increased by greater than 100% and the platelet content of PBPC products by 60% to 110% on the first and second days of aphereses (P &lt; .0001) with the greatest effect seen with repeated dosing of rhTPO at 0.6 μg/kg. rhTPO is safe and well tolerated as a mobilizing agent before PBPC collection. Mobilization with rhTPO and G-CSF, in comparison to a comparable, nonrandomized G-CSF–mobilized group of patients, decreases the number of apheresis procedures required, may accelerate hematopoietic recovery, and may reduce the number of transfusions required following high-dose chemotherapy for breast cancer.

Automated counting of platelets on the Bayer ADVIA 120 analyser

Precise counting of platelets is difficult particularly in the low thrombocytopenic range or when large platelets exist. The recently available Bayer ADVIA 120 analyser uses a method of counting platelets based on two dimensional laser light scatter. We have evaluated this technique on an analysis of 217 peripheral blood samples and found significant differences in platelet counts compared with values obtained by impedance technology, when the causes of thrombocytopenia were due to peripheral platelet consumption. Moreover, such differences were more marked in those samples from severely thrombocytopenic individuals with large platelets on the blood film. These differences, which warrant further study, may have significant implications for the management of patients with very low platelet counts.

Fibrinogen-coated albumin microcapsules reduce bleeding in severely thrombocytopenic rabbits

Severe thrombocytopenia frequently occurs in patients receiving chemotherapy and in patients with autoimmune disorders. Thrombocytopenia is associated with bleeding, which may be serious and life threatening. Current treatment strategies for thrombocytopenia may require transfusion of allogeneic platelets, which is associated with serious drawbacks. These include the occurrence of anti-platelet antibodies, which may result in refractoriness to further platelet transfusions, and the potential risk of transfer of blood-borne diseases. Therefore, we have recently developed a platelet substitute product (Synthocytes), which is composed of human albumin microcapsules with fibrinogen immobilized on their surface. Here we show that the intravenous administration of these microcapsules not only corrects the prolonged bleeding time in rabbits rendered thrombocytopenic either by anti-platelet antibodies or by chemotherapy, but also reduces bleeding from surgical wounds inflicted in the abdominal skin and musculature. No potential systemic prothrombotic effect of the microcapsules was observed in a model of rabbit venous thrombosis. As for the mechanism of action, experiments with normal and thrombocytopenic human blood in an endothelial cell matrix-coated perfusion chamber demonstrated an interaction between the fibrinogen-coated albumin microcapsules and native platelets. It was shown that the fibrinogen-coated albumin microcapsules could facilitate platelet adhesion to endothelial cell matrix and correct the impaired formation of platelet aggregates in relatively platelet-poor blood. This study indicates that fibrinogen-coated albumin microcapsules can act to improve primary hemostasis under thrombocytopenic conditions and may eventually be a promising agent for prophylaxis and treatment of bleeding in patients with severe thrombocytopenia.

Changes in platelet demand in association with the spread of autologous peripheral blood progenitor cell transplantation

Changes in platelet demand accompanying widespread application of autologous peripheral blood progenitor cell transplantation (APBPCT) were anticipated. The differences in the transfused volume of platelet concentrate (PC) among 8 patients with malignant lymphoma who were treated with APBPCT and 10 patients with malignant lymphoma who were not treated with APBPCT, although peripheral blood progenitor cell harvests had been performed, were studied. The former was 81 Japanese PC units more than the latter. Considering the supplied volume of PC from Red Cross blood centers and the number of APBPCTs in 1996 in Japan, the Japanese demand for PC increases by 0.16% for enforced APBPCT versus 0.36%, which includes the PC demand necessary in all treatment courses. The total increment in PC demand associated with APBPCT is not large enough to threaten the PC supply of Japan even if the number of APBPCTs increases rapidly.

Platelet Transfusion: A Dose-Response Study

Early recommendations on prophylactic transfusion of thrombocytopenic patients involved a standard platelet dose of about 0.5 × 1011/10 kg body weight. Given the lack of data supporting this dose, we prospectively studied the dose response to platelet transfusions in adults and children with hematologic malignancies. Each patient received, in similar clinical conditions, a medium, high, and very high dose of fresh (< 24 hours old) ABO-compatible platelets, in the form of apheresis platelet concentrates (APC). For the adults, the medium dose was defined as APC containing between 4 and 6 × 1011 platelets, the high dose between 6 and 8 × 1011, and the very high dose > 8 × 1011; for the children, the three doses corresponded to 2 to 4, 4 to 6, and > 6 × 1011 platelets. The end points were the platelet increment, platelet recovery, and the transfusion interval, and the results were compared with a paired t-test. Sixty-nine adults and 13 children could be assessed. Recoveries in the adults were similar with the three doses (from 28% to 30%), but the high and very high doses led to a significantly better platelet increment (52 and 61 × 109/L, respectively) than the medium dose (33 × 109/L, P < .01). The main difference was in the transfusion interval, which increased with the dose of platelets transfused, from 2.6 days with the medium dose to 3.3 and 4.1 days with the high and very high doses, respectively (P< .01). The positive effect of the high dose was observed regardless of pretransfusional clinical status, but was more marked in patients with no clinical factors known to impair platelet recovery. In these patients, a platelet dose of 0.07 × 1011 per kg of body weight led to a transfusion interval of more than 2 days in 95% of cases. In patients with clinical factors favoring platelet consumption, the proportion of transfusions yielding an optimal platelet increment and transfusion interval increased with the dose of platelets.The platelet dose-effect was also significant in the children, in whom the high and very high doses led to 1.5-fold to twofold higher posttransfusion platelet counts and transfusion intervals. We conclude that transfusion of high platelet doses can reduce the number of platelet concentrates required by thrombocytopenic patients and significantly reduce donor exposure.

© 1998 by The American Society of Hematology.

Platelet Transfusion: A Dose-Response Study

Early recommendations on prophylactic transfusion of thrombocytopenic patients involved a standard platelet dose of about 0.5 × 1011/10 kg body weight. Given the lack of data supporting this dose, we prospectively studied the dose response to platelet transfusions in adults and children with hematologic malignancies. Each patient received, in similar clinical conditions, a medium, high, and very high dose of fresh (&lt; 24 hours old) ABO-compatible platelets, in the form of apheresis platelet concentrates (APC). For the adults, the medium dose was defined as APC containing between 4 and 6 × 1011 platelets, the high dose between 6 and 8 × 1011, and the very high dose &gt; 8 × 1011; for the children, the three doses corresponded to 2 to 4, 4 to 6, and &gt; 6 × 1011 platelets. The end points were the platelet increment, platelet recovery, and the transfusion interval, and the results were compared with a paired t-test. Sixty-nine adults and 13 children could be assessed. Recoveries in the adults were similar with the three doses (from 28% to 30%), but the high and very high doses led to a significantly better platelet increment (52 and 61 × 109/L, respectively) than the medium dose (33 × 109/L, P &lt; .01). The main difference was in the transfusion interval, which increased with the dose of platelets transfused, from 2.6 days with the medium dose to 3.3 and 4.1 days with the high and very high doses, respectively (P&lt; .01). The positive effect of the high dose was observed regardless of pretransfusional clinical status, but was more marked in patients with no clinical factors known to impair platelet recovery. In these patients, a platelet dose of 0.07 × 1011 per kg of body weight led to a transfusion interval of more than 2 days in 95% of cases. In patients with clinical factors favoring platelet consumption, the proportion of transfusions yielding an optimal platelet increment and transfusion interval increased with the dose of platelets.The platelet dose-effect was also significant in the children, in whom the high and very high doses led to 1.5-fold to twofold higher posttransfusion platelet counts and transfusion intervals. We conclude that transfusion of high platelet doses can reduce the number of platelet concentrates required by thrombocytopenic patients and significantly reduce donor exposure.

© 1998 by The American Society of Hematology.

Thrombocytopenia-Platelet Support or Growth Factors?

The prevention and treatment of hemorrhage in patients with severe thrombocytopenia following cytotoxic chemotherapy and/or radiotherapy remain important issues in the supportive care of these patients. Platelet transfusions have been available for this purpose for over 30 years, and there have been recent initiatives to refine the way in which they are used and to improve their safety. An alternative to platelet transfusions is the enhancement of platelet recovery through the use of hemopoietic growth factors, and the recent identification of thrombopoietin and its potential for clinical use are exciting developments. Further work is needed to ensure its safety, and to define the appropriate indications for its use. Another alternative to platelet transfusions is the use of platelet substitutes, and a number of products are being developed. The clinical use of hemopoietic growth factors and platelet substitutes raises the prospect of reducing the current high demand for platelet concentrates. However, it remains to be seen whether their potential will be fully realised, and platelet transfusions will continue to be needed for the forseeable future.