Platelet Immunopathology and Therapy: A Canadian Blood Services Research and Development Symposium

Evaluation of Platelet Alloimmunization by Filtration Enzyme-Linked Immunosorbent Assay

The current methods for detecting antiplatelet antibodies are mostly manual and labor-intensive. A convenient and rapid detection method is required for effectively detecting alloimmunization during platelet transfusion. In our study, to detect antiplatelet antibodies, positive and negative sera of random-donor antiplatelet antibodies were collected after completing a routine solid-phase red cell adherence test (SPRCA). Platelet concentrates from our random volunteer donors were also prepared using the ZZAP method and then used in a faster, significantly less labor-intensive process, a filtration enzyme-linked immunosorbent assay (fELISA), for detecting antibodies against platelet surface antigens. All fELISA chromogen intensities were processed using ImageJ software. By dividing the final chromogen intensity of each test serum with the background chromogen intensity of whole platelets, the reactivity ratios of fELISA can be used to differentiate positive SPRCA sera from negative sera. A sensitivity of 93.9% and a specificity of 93.3% were obtained for 50 μL of sera using fELISA. The area under the ROC curve reached 0.96 when comparing fELISA with the SPRCA test. We have successfully developed a rapid fELISA method for detecting antiplatelet antibodies.

Evaluation and management of platelet transfusion refractoriness

Platelet transfusion refractoriness (PTR), in which platelet counts do not increase after transfusion, occurs in many patients receiving platelet transfusions. PTR is a clinical condition that can harm patients. The causes of PTR can be divided into two types: immune and non-immune. Most cases of PTR are non-immune. Among immune causes, the most common is human leukocyte antigen (HLA) class I molecules. PTR caused by anti-HLA antibodies is usually managed by transfusing HLA-matched platelets. Therefore, it is important, especially for hemato-oncologists who frequently perform transfusion, to accurately diagnose whether the cause of platelet transfusion failure is alloimmune or non-immunological when determining the treatment direction for the patient. In this review, we discuss the definitions, causes, countermeasures, and prevention methods of PTR.

Clinical and immunological features of platelet transfusion refractoriness in young patients with de novo acute myeloid leukemia

Platelet transfusion is important in the prevention and treatment of bleeding in patients with acute myeloid leukemia (AML) after receiving intensive chemotherapy. However, platelet transfusion refractoriness (PTR) is an intractable clinical issue occurred in these patients. And its clinical and immunological features remain largely unknown. The potential causes and clinical features of PTR were retrospectively analyzed in 560 patients who were diagnosed as de novo AML in Tongji Hospital from June 2012 through June 2018. A high‐throughput antibody screening for the detection of human leukocyte antigen (HLA) and its serotypes was performed in 133 newly diagnosed AML patients. PTR occurred in 11.8% of the de novo AML patients. The median age for patients with PTR was 46 years (range, 15‐70). It frequently manifested in female patients and in patients with splenomegaly, M4 subtype, c‐Kit gene mutation, and rearrangements of RUNX1‐RUNX1T1 or CBFB‐MYH11, commonly referred to as core binding factor AML (CBF‐AML). Notably, CBF‐AML was independently associated with the occurrence of PTR. PTR predominantly developed in patients who had CBF‐AML (P < .001) and in patients who further had better minimal residual disease (MRD) reduction (≥3‐log) before the second consolidation chemotherapy (P = .007). HLA‐I antibodies were detected in the serum of 9.0% of AML patients and markedly enriched in patients with PTR (P < .001) and in patients with CBF‐AML (P = .018). HLA‐B was the most frequently identified serum epitope in PTR patients. Patients with CBF‐AML had higher tendency to develop HLA‐I antibodies and PTR, which depicted novel features of PTR in AML and might provide insights into its efficient managements.

Platelet transfusion refractoriness in patients with acute myeloid leukemia treated by intensive chemotherapy

Platelet transfusion refractoriness (PTR) is a major adverse event in the management of acute myeloid leukemia (AML). In a series of 897 adult patients with AML receiving intensive chemotherapy, we identified 41 patients (4.8%) with PTR. PTR was more frequently observed in parous women, patients with extra-medullary disease, a low white blood cell count, an infection, or hemophagocytic syndrome. Among the 31 patients with anti-human leucocyte antigen (HLA) antibodies, an HLA-matched donor was identified for 18 patients (58.1%). Median time between diagnosis of PTR and the first HLA-matched transfusion was 12.5days. HLA-matched transfusions induced a significant increment in platelet counts in 37% of cases. Thrombopoietin receptor agonists were given to 10 patients but did not shorten the duration of thrombocytopenia, reduce severe bleeding, or early death. Grade 3-4 bleeding events during induction, early death caused by bleeding, and death caused by bleeding at any time were significantly greater in patients that had platelet transfusion refractoriness (22% vs. 4.1%, P<0.0001; 12.2% vs. 1.4%, P=0.0006; and 24.4% vs. 5.3%, P<0.0001; respectively). PTR during chemotherapy for AML significantly increased the risk of early and late deaths caused by a severe bleeding event. Improved understanding of platelet destruction is needed to design mechanism-based therapeutic strategies.

Blood-Borne Pathogens: A Canadian Blood Services Centre for Innovation Symposium

Testing donations for pathogens and deferring selected blood donors have reduced the risk of transmission of known pathogens by transfusion to extremely low levels in most developed countries. Protecting the blood supply from emerging infectious threats remains a serious concern in the transfusion medicine community. Transfusion services can employ indirect measures such as surveillance, hemovigilance, and donor questioning (defense), protein-, or nucleic acid based direct testing (detection), or pathogen inactivation of blood products (destruction) as strategies to mitigate the risk of transmission-transmitted infection. In the North American context, emerging threats currently include dengue, chikungunya, and hepatitis E viruses, and Babesia protozoan parasites. The 2003 SARS and 2014 Ebola outbreaks illustrate the potential of epidemics unlikely to be transmitted by blood transfusion but disruptive to blood systems. Donor-free blood products such as ex vivo generated red blood cells offer a theoretical way to avoid transmission-transmitted infection risk, although biological, engineering, and manufacturing challenges must be overcome before this approach becomes practical. Similarly, next generation sequencing of all nucleic acid in a blood sample is currently possible but impractical for generalized screening. Pathogen inactivation systems are in use in different jurisdictions around the world, and are starting to gain regulatory approval in North America. Cost concerns make it likely that pathogen inactivation will be contemplated by blood operators through the lens of health economics and risk-based decision making, rather than in zero-risk paradigms previously embraced for transfusable products. Defense of the blood supply from infectious disease risk will continue to require innovative combinations of surveillance, detection, and pathogen avoidance or inactivation.

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A symposium on blood-borne pathogens was held September 26, 2015, in Toronto, Canada.

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Transmission-transmitted infections remain a threat to the blood supply.

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The residual risk from established pathogens is small; emerging agents are a concern.

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Next generation sequencing and donor-free blood are not yet practical approaches.

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Pathogen inactivation technology is being increasingly used around the world.

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Health economic concerns will likely guide future advances in this area.

Plasma and Plasma Protein Product Transfusion: A Canadian Blood Services Centre for Innovation Symposium

Plasma obtained via whole blood donation processing or via apheresis technology can either be transfused directly to patients or pooled and fractionated into plasma protein products that are concentrates of 1 or more purified plasma protein. The evidence base supporting clinical efficacy in most of the indications for which plasma is transfused is weak, whereas high-quality evidence supports the efficacy of plasma protein products in at least some of the clinical settings in which they are used. Transfusable plasma utilization remains composed in part of applications that fall outside of clinical practice guidelines. Plasma contains all of the soluble coagulation factors and is frequently transfused in efforts to restore or reinforce patient hemostasis. The biochemical complexities of coagulation have in recent years been rationalized in newer cell-based models that supplement the cascade hypothesis. Efforts to normalize widely used clinical hemostasis screening test values by plasma transfusion are thought to be misplaced, but superior rapid tests have been slow to emerge. The advent of non-vitamin K-dependent oral anticoagulants has brought new challenges to clinical laboratories in plasma testing and to clinicians needing to reverse non-vitamin K-dependent oral anticoagulants urgently. Current plasma-related controversies include prophylactic plasma transfusion before invasive procedures, plasma vs prothrombin complex concentrates for urgent warfarin reversal, and the utility of increased ratios of plasma to red blood cell units transfused in massive transfusion protocols. The first recombinant plasma protein products to reach the clinic were recombinant hemophilia treatment products, and these donor-free equivalents to factors VIII and IX are now being supplemented with novel products whose circulatory half-lives have been increased by chemical modification or genetic fusion. Achieving optimal plasma utilization is an ongoing challenge in the interconnected worlds of transfusable plasma, plasma protein products, and recombinant and engineered replacements.

Safety of endoscopic interventions in patients with thrombocytopenia

BACKGROUND

The risk of endoscopic interventions in thrombocytopenia has received little attention in the medical literature.

OBJECTIVE

The aim of this study was to assess the safety of endoscopic interventions including evaluation of GI bleeding (GIB) in patients with thrombocytopenia.

DESIGN AND SETTING

Retrospective study, tertiary oncology center.

PATIENTS AND INTERVENTION

Review of consecutive endoscopies with preprocedure platelet counts (PCs) of 75 × 10(3)/μL or lower.

MAIN OUTCOME MEASUREMENTS

Risk of bleeding with routine endoscopic interventions and transfusion requirement after evaluation of GIB.

RESULTS

A total of 617 (351 upper, 266 lower [90 colonoscopies]) endoscopies were performed in 395 patients. Forceps-biopsy specimens were obtained in 398 endoscopies (mean ± standard deviation [SD] PC: 38.21 ± 11.7 × 10(3)/μL) and 45 polypectomies were performed in 17 endoscopies (mean ± SD PC: 39.65 ± 8.53 × 10(3)/μL). The risk of bleeding was 1.5% (6 of 398 endoscopies) at the biopsy site and 4% (2 of 45 polypectomies) at the polypectomy site. Active GIB (mean ± SD PC: 32.85 ± 4.0 × 10(3)/μL) was observed in 68 (11% of 617) endoscopies and intervention (mean ± SD PC: 33.68 ± 4.6 × 10(3)/μL) was performed in 41 procedures. Together, angiodysplasias and ulcers were the most common etiology (51.2% of 41). Hemostasis was achieved in 39 (95.1% of 41) procedures. Comparison of blood transfusions ± 3 days of successful therapy showed a 52% reduction (P < .001). By multivariate analysis, a higher aggregate blood transfusion 3 days preceding endoscopy (odds ratio 1.32; 95% confidence interval, 1.16-1.50; P < .001) predicted endoscopic findings of active GIB.

LIMITATIONS

Retrospective design, single center.

CONCLUSIONS

In the largest endoscopic experience reported in thrombocytopenic patients (Common Terminology Criteria for Adverse Events grade 3 or lower), bleeding caused by standard forceps biopsy and polypectomy (≤10 mm) was minor and easily controlled. Endoscopic therapy for GIB is safe and significantly reduces the packed red blood cell requirement and should be considered in patients with thrombocytopenia in the setting of an appropriate transfusion strategy.

Identification of platelet refractoriness in oncohematologic patients

OBJECTIVES

To identify the occurrence and the causes of platelet refractoriness in oncohematologic patients.

INTRODUCTION

Platelet refractoriness (unsatisfactory post-transfusion platelet increment) is a severe problem that impairs the treatment of oncohematologic patients and is not routinely investigated in most Brazilian services.

METHODS

Forty-four episodes of platelet concentrate transfusion were evaluated in 16 patients according to the following parameters: corrected count increment, clinical conditions and detection of anti-platelet antibodies by the platelet immunofluorescence test (PIFT) and panel reactive antibodies against human leukocyte antigen class I (PRA-HLA).

RESULTS

Of the 16 patients evaluated (median age: 53 years), nine (56%) were women, seven of them with a history of pregnancy. An unsatisfactory increment was observed in 43% of the transfusion events, being more frequent in transfusions of random platelet concentrates (54%). Platelet refractoriness was confirmed in three patients (19%), who presented immunologic and non-immunologic causes. Alloantibodies were identified in eight patients (50%) by the PIFT and in three (19%) by the PRA-HLA. Among alloimmunized patients, nine (64%) had a history of transfusion, and three as a result of pregnancy (43%). Of the former, two were refractory (29%). No significant differences were observed, probably as a result of the small sample size.

CONCLUSION

The high rate of unsatisfactory platelet increment, refractoriness and alloimmunization observed support the need to set up protocols for the investigation of this complication in all chronically transfused patients, a fundamental requirement for the guarantee of adequate management.