Platelet Antibodies Research Articles

Platelet antibody detection assays: a single-laboratory comparison of MAIPA, PIFT, and microsphere-based multiplex assays Pak-Lx

Background and ObjectivesThe identification of platelet antibodies is essential for diagnosing and managing conditions such as fetal and neonatal alloimmune thrombocytopenic purpura, post-transfusion purpura, and immune platelet refractoriness. Monoclonal antibody immobilization of platelet antigens (MAIPA) is the standard method for detecting anti-human platelet antigen (HPA) antibodies, while the detection of anti-HLA antibodies once relied on the complement-dependent cytotoxicity method, however advanced technologies such as enzyme-linked immunosorbent assay and Luminex have significantly improved sensitivity and accuracy in identifying these antibodies. Flow cytometry-based techniques (platelet immunofluorescence test - PIFT) and Luminex platform-driven microsphere-based multiplex assays (Pak-Lx) are widely employed in platelet immunology laboratories owing to their remarkable flexibility and versatility. The present study compared the sensitivity, specificity, and concordance of these different serological techniques used in platelet antibody identification. Material and MethodsOne hundred serum samples from patients suspected of immune-mediated platelet disorders were examined. Initially, the samples underwent testing using the MAIPA method. Subsequently, the results were compared with three alternative methods: PIFT and microsphere-based multiplex assays for both HLA and HPA antibodies. ResultsPak-Lx demonstrated a 94 % agreement with MAIPA, while PIFT had 88 % agreement for HPA antibodies. For HLA antibody detection, Pak-Lx versus DLX had 75 % concordance, MAIPA versus DLX showed 77 %, and PIFT versus DLX displayed an 81 % concordance rate. Remarkably, there were no significant differences in concordance levels between Pak-Lx and PIFT compared to MAIPA and DLX for anti-HPA and HLA antibodies, respectively. ConclusionThis study found no significant differences in concordance among the tested assays for detecting anti-HPA and anti-HLA antibodies. These data suggest that no single method can detect all clinically important antibodies. Therefore, it is advisable that each laboratory develops customized protocols based on their expertise and employs complementary methods for comprehensive patient assessments.

Investigation of the correlation between platelet antibodies and peripheral blood cytopenia in patients with hepatocellular carcinoma

The primary triggers that stimulate the body to generate platelet antibodies via immune mechanisms encompass events such as pregnancy, transplantation, and blood transfusion. Interestingly, our findings revealed that a subset of male patients with hepatocellular carcinoma (HCC), despite having no history of transplantation or blood transfusion, has shown positive results in platelet antibody screenings. This hints at the possibility that certain factors, potentially related to the tumor itself or its treatment, may affect antibody production. To delve the causes we initiated this study. We employed a case–control study approach to analyze potential influential factors leading to the positive results via univariate and multivariate regression analysis. We utilized Kendall’s tau-b correlation to examine the relationship between the strength of platelet antibodies and peripheral blood cytopenia. Antitumor medication emerged as an independent risk factor for positive results in HCC patients, and the strength of platelet antibodies positively correlated with the severity of anemia and thrombocytopenia. Without history of blood transfusion, transplantation, pregnancy, those HCC patients underwent recent tumor medication therapy are experiencing peripheral erythrocytopenia or thrombocytopenia, for them platelet antibody screenings holds potential clinical value for prevention and treatment of complications like drug-immune-related anemia and/or bleeding.

Place of HPA1a Antigen in Neonatal Thrombocytopenia in Gyneco-Obstetric and Pediatric Hospital of Douala and Laquintinie Hospital of Douala

Background: Platelet antigens called human platelet antigens (HPA) present on the surface of platelets are involved in immunological conflicts, sometimes leading to severe thrombocytopenia related to anti-HPA1a antibodies. The aim of this study was to detect platelet antibodies in newborns and the associated risk factors. Methods: We conducted a cross-sectional analytical study from 05 January to 30 June 2017 at the Laquintinie Hospital of Douala and the Gyneco-Obstetric and Pediatric Hospital of Douala among newborns with thrombocytopenia and mothers in compliance with ethical considerations. Socio-demographic and clinical data were collected. Blood was collected on EDTA tubes for newborns and on tubes without anticoagulants for mothers in order to determine the presence of anti-HPA1a antibodies. Statistical analysis was performed using SPSS version 22 software. Results: A total of 35 newborns and 35 mothers were recruited in this study. The mean age of the newborns was 8.5 ± 7.2 days, with a sex ratio of 1.7% in favor of boys. The prevalence of neonatal thrombocytopenia was 4.1%, and the prevalence of HPA1a antibody was 17.1%. Most of the newborns were born to primiparous mothers (57.1%), and 80.0% had prematurity and neonatal jaundice as reasons for hospitalization. Male newborns and those whose mothers had been transfused at least once during or before pregnancy had respectively 4 (OR = 3.53; P-value < 0.0001) and 14 (OR = 14; P-value = 0.0483) times more risk of having the anti-HPA1a antibody. Conclusion: Our study has shown that the anti-HPA1a antibody is a risk factor for neonatal thrombocytopenia and is associated with maternal transfusion.

Establishment and clinical application of the HLA genotype database of platelet-apheresis donors in Suzhou

The establishment of a platelet-apheresis donor database may provide a feasible solution to improve the efficacy of platelet transfusion in patients with immune platelet transfusion refractoriness (PTR). This study aimed to establish HLA genotype database in Suzhou, to provide HLA-I compatible platelets for PTR patients to ensure the safety and effectiveness of platelet transfusions. We used a polymerase chain reaction sequence-based typing (PCR-SBT) method to establish the database by performing high-resolution HLA-A, -B, and –C genotyping on 900 platelet-apheresis donors. HLA-I antibody was detected in patients using a Luminex device, and HLA-I gene matching was performed by an HLA-Matchmaker. We found that the highest frequency of the HLA-A allele was A*11:01 (17.06 %), followed by A*24:02 (14.67 %) and A*02:01 (13.61 %). The highest frequency of the HLA-B allele was B*46:01 (9.78 %), followed by B*40:01 (8.39 %) and B*13:02 (33 %). After the detection of platelet antibodies in 74 patients with immune PTR, we found 30 HLA-A antibodies and 48 HLA-B antibodies, and there were a variety of high frequency antibodies whose alleles were low in the donor database, such as HLA-A*68:02, and B*57:01. After avoiding donor-specific antibodies (DSA) matching, 102 of 209 platelet-compatible transfusions were effective, resulting in an effective rate of 48.8 %, which significantly improved the efficacy of platelet transfusion. The establishment of a platelet donor database is of great significance to improve the therapeutic effect of platelet transfusion in patients with hematologic disorder, and save blood resources, and it is also the premise and guarantee of precise platelet transfusion.

Analysis of transfusion effect of different platelet matching schemes in patients with platelet transfusion refractoriness

Objective: To analyze the transfusion effect of different platelet matching schemes in patients with platelet transfusion refractoriness (PTR). Methods: A total of 94 patients with PTR received by Taiyuan Blood Center from January to December 2021 were retrospectively analyzed, including 26 males and 68 females, aged 53(34,66) years. Platelet antibody screening was performed by enzyme-linked immunosorbent assay (ELISA). For patients with positive human leukocyte antigen (HLA) class Ⅰ antibodies, Luminex platform liquid chip assay was used to identify the specificity of antibodies, and platelets with missing allelic expression antigen corresponding to their specific antibodies were found in the platelet donor gene database established in our laboratory. For patients with negative class HLA-Ⅰ antibody screening, medium and high-resolution HLA-A and B alleles were genotyped by polymerase chain reaction restriction sequence specific oligonucleotide (PCR-SSO), and the compatible platelets were searched from the platelet donor gene database by HLA cross-reactive group genotype matching scheme or directly selected by serological cross-matching. The PCI compliance rate and total transfusion effective rate of different mismatch site groups and different matching scheme groups were statistically analyzed. Results: Platelet antibody was detected in 39 of 94 PTR patients with a positive rate of 41.5%, and all of them were HLA-Ⅰ antibodies, and 1 case was accompanied by human platelet antigen (HPA) antibody. A total of 134 times of compatible platelets were supplied to 39 patients with HLA-Ⅰ antibody positive by using antibody avoidance matching method. And the total effective rate of transfusion was 97.8% (131/134); The PCI compliance rates of HLA-A antigen mismatch, HLA-B antigen mismatch and HLA-A and B antigen mismatch groups were 81.6% (31/38), 86.5% (32/37) and 78.6% (22/28), respectively. The total effective rate of transfusion was 97.4% (37/38), 94.6% (35/37) and 100% (28/28), respectively, with no statistical significance (all P>0.05). A total of 118 times of compatible platelets were provided by HLA antigen cross-reaction group genotype matching and serological cross-matching, 90 transfusion effects were collected during follow-up, and the total effective rate was 76.7% (69/90). Conclusion: The combination of different platelet matching schemes can improve the PCI compliance rate and the total effective rate of transfusion in PTR patients.

Efficacy and safety of eltrombopag in the treatment of primary immune thrombocytopenia: real-world data from a single medical center

Objective: This study aimed at investigating the efficacy and safety of eltrombopag in the treatment of adult primary immune thrombocytopenia (ITP) and evaluated the factors influencing its efficacy and side effects. Methods: A total of 198 patients with adult ITP who were admitted to Tianjin Medical University General Hospital between January 2018 and March 2022 were retrospectively analyzed. The efficacy of each starting dose of eltrombopag was evaluated, and adverse events were analyzed. The factors influencing efficacy were investigated, including sex, age, adult ITP type, platelet antibodies, and combined drug treatments. Results: Of the 198 patients, 70 males and 128 females with a median age of 45 years (18-88 years) were included; 130 (65.7%) had newly diagnosed adult ITP, 25 (12.6%) had persistent adult ITP, and 43 (21.7%) had chronic adult ITP. The bleeding event scores at baseline were assessed; 84.3% had scores of<4 and 15.7% had scores of ≥4. The eltrombopag response rate (initial response) at 6 weeks was 78.8% (complete response [CR]: 49.0%; CR1: 14.6%; CR2: 15.2%). The median response time to eltrombopag was 7 (7, 14) days. The initial response rates to 25, 50, and 75 mg eltrombopag were 74.1%, 85.9%, and 60.0%, respectively (P=0.031). The initial response rate to the 50 mg dose was significantly higher than that of the 25-mg and 75-mg doses. Two patients received 100 mg as the starting dose, and their initial response was 0. Regarding dose adjustment, 70.7% of the patients remained on the starting dose, 8.6% underwent dose adjustment to 50 mg, and 6.1% underwent dose adjustment to 75 mg. Another two patients underwent dose adjustment to 100 mg. After dose adjustment, the persistent response rates were 83.6%, 85.3%, and 85.7% for the 25-, 50-, and 75-mg doses, respectively, with no significant difference. After dose adjustment, the sustained efficacy rate for the 100-mg dose (4 patients) was 100.0%. After 6 weeks of treatment with eltrombopag, the overall bleeding score of patients with ITP decreased. The number of patients with a score of ≥4 decreased to 0, the number of patients with a score of<4 decreased, and there was no significant change in the number of patients with a score of 1-2. The most common adverse event associated with eltrombopag was impaired liver function (7.7%). No thrombosis events or other adverse events were observed. ITP type and number of megakaryocytes significantly affected the initial response to eltrombopag. The initial response rates to eltrombopag for newly diagnosed adult ITP, persistent adult ITP, and chronic adult ITP were 85.3%, 56.0%, and 76.2%, respectively (P=0.003). For megakaryocytes, the initial response rates were 61.8%, 87.1%, and 84.3% (P=0.009) for the decreased, normal, and increased megakaryocyte groups, respectively. Conclusion: Eltrombopag, as a second-line or higher treatment for adult ITP, has a rapid onset of action and good safety. The initial response rate is significantly higher with a dose of 50 mg than with a dose of 25 mg. Patients with newly diagnosed ITP and those with normal or increased megakaryocyte numbers have a higher initial response rate to eltrombopag.

Optimization of Platelet-Rich Plasma Preparation for Regenerative Medicine: Comparison of Different Anticoagulants and Resuspension Media.

Platelet-rich plasma (PRP) has emerged as a promising therapy in regenerative medicine. However, the lack of standardization in PRP preparation protocols presents a challenge in achieving reproducible and accurate results. This study aimed to optimize the PRP preparation protocol by investigating the impact of two different anticoagulants, sodium citrate (SC) and ethylenediaminetetraacetic acid (EDTA), and resuspension media, plasma versus sodium chloride (NaCl). Platelet recovery rates were calculated and compared between groups, in addition to platelet activity and vascular endothelial growth factor (VEGF) released into plasma after PRP activation. The platelet recovery rate was higher with EDTA in comparison to SC (51.04% vs. 29.85%, p = 0.005). Platelet activity was also higher, with a higher expression of two platelet antibodies, platelet surface P-Selectin (CD62p) and PAC-1, in the EDTA group. The concentration of VEGF was higher with SC in comparison to EDTA (628.73 vs. 265.44 pg/mL, p = 0.013). Platelet recovery rates and VEGF levels were higher in PRP resuspended in plasma when compared to NaCl (61.60% vs. 48.61%, p = 0.011 and 363.32 vs. 159.83 pg/mL, p = 0.005, respectively). Our study reinforces the superiority of EDTA (as anticoagulant) and plasma (for resuspension) in obtaining a higher platelet recovery and preserving platelet functionality during PRP preparation.

Use of Plasmapheresis in Heparin Induced Thrombocytopenia in Patients Undergoing Urgent Cardiac Surgery

Abstract Heparin Induced Thrombocytopenia (HIT) is a potentially life-threatening but uncommon disease process characterized by IgG antibodies that recognize platelet factor 4/heparin immune complexes causing thrombocytopenia and thrombosis. Although therapeutic plasmapheresis (PLEX) appears to be effective, protocols regarding how and when to institute PLEX remain elusive. At our institution, we put together a standardized approach to assess the interventional success across patients that included 1 plasmapheresis procedure per day over 4 days, processing one plasma volume and using thawed plasma as the replacement fluid. Treatment effectiveness was evaluated by pre- and post-interventional HIPA OD levels and platelet count. Treatment aim was to decrease the HIPA OD to less than 0.6 and obtain a normal platelet count. The aim of this study was to design a protocol for PLEX to address urgent need for patients with HIT for which heparin is planned for intraoperative cardiac surgery requiring cardiopulmonary bypass (CPB) anticoagulation. We retrospectively examined the medical records of 2 HIT-positive patients who underwent PLEX prior to cardiac surgery at our large quaternary care hospital. Both patients had a 4Ts score of 5, with a medium probability of disease. One patient's HIT was confirmed by a positive serotonin release assay (SRA). The second patient had persistently negative confirmatory test but was deemed clinical HIT. The first patient is a 53-year-old female, who was admitted for mitral valve replacement, aortic valve replacement, and tricuspid valve repair. She was confirmed HIT by positive SRA. Three sessions of PLEX were performed on consecutive days. Her HIPA (heparin induced platelet antibody) O.D. value decreased from 1.925 to 0.534 and platelet counts normalized. The second patient is a 73-year-old male, who was admitted for LVAD implantation and LV thrombus resection. Two sessions of PLEX were performed on consecutive days. His HIPA O.D. value deceased from 1.261 to &amp;lt; 0.4 (negative) and platelet counts normalized. For both patients, the last PLEX procedure was performed the day of surgery, and the cardiac surgical procedure was completed successfully. Based on these 2 patients, we have proposed a protocol for PLEX in HIT patients as follows: daily plasmapheresis x 4 days will be performed until the OD has decreased to less than 0.6 and platelet count has normalized. Each plasmapheresis will consist of the processing of one plasma volume, using thawed plasma as the replacement fluid. The last plasmapheresis will occur on the day of surgery prior to surgery. Further assessment will be performed if the targeted parameters have not been met by the 4th plasmapheresis procedure. In conclusion, we present 2 patients with HIT who benefitted from PLEX prior to cardiac surgery under CPB. We will adopt the protocol used for these 2 patients as our standard of practice moving forward.

Analysis of Influencing Factors of Positive Antiplatelet Antibody in Patients with Diffuse Large B-Cell Lymphoma

Background Diffuse large B-cell lymphoma (DLBCL) is a common malignant tumor of the hematological system. Chemotherapy is the main treatment. As a cytotoxic drug, chemotherapeutic drugs can lead to thrombocytopenia, increase the risk of bleeding and require platelet transfusion if necessary. Since platelet antibody is the main cause of ineffective platelet transfusion, the detection of platelet antibody is of great significance to prevent the inefficacy of platelet transfusion in patients with diffuse large B-cell lymphoma. Objective To analyze the screening results of antiplatelet antibodies in patients with diffuse large B-cell lymphoma and to explore the main factors affecting the production of antiplatelet antibodies so as to provide basis for safe blood transfusion. Methods Patients with diffuse large B-cell lymphoma treated in our department from August 2022 to May 2023 were selected as subjects. Antiplatelet antibodies (GP IX, GP Ⅰ b, GPIIb, GPIIa, GMP140) were detected by flow cytometry. The factors affecting the positive antiplatelet antibodies were analyzed from the aspects of clinical characteristics and laboratory indexes. Results In 155 patients with diffuse large B-cell lymphoma, the positive rate of antiplatelet antibody was 63.23% (98/155). Among them, the positive rate of antiplatelet antibody in male patients was 63.75% (51/80), higher than that in female patients was 62.67%(47/75), and the difference was statistically significant (P&amp;lt;0.05). The positive rate of antiplatelet antibody in patients over 60 years old was 65.18% (43/67), higher than that in patients aged ≤ 60 years old was 62.5%(55/88). The difference was statistically significant (P&amp;lt;0.05). In addition, the positive detection of antiplatelet antibody was related to the abnormal results of large platelet ratio, mean platelet volume, D-dimer and aspartate aminotransferase. In the positive distribution of antiplatelet antibodies, the positive rates of GP IX, GP Ⅰ b, GPIIb, GPIIa and GMP140 autoantibodies were 1.29% (2/155), 29.03% (45/155), 37.42% (58/155), 1.29% (2/155), 49.68% (77/155), respectively. The positive number of antiplatelet antibodies was related to the abnormal results of partial prothrombin time, prothrombin time, prothrombin activity, international standardized ratio, thrombin time, fibrin (prothrombin) degradation products, globulin, alanine aminotransferase and aspartate aminotransferase. Conclusion Patients with diffuse large B-cell lymphoma with abnormal results of large platelet ratio, mean platelet volume, D-dimer and aspartate aminotransferase should pay attention to the detection of antiplatelet antibodies before platelet transfusion to prevent transfusion failure.

Avatrombopag Safe and Effective in Treatment of Severe Refractory Thrombocytopenia in a Pediatric Patient with Philadelphia Chromosome Positive Acute Lymphoblastic Leukemia Following Allogeneic Hematopoietic Stem Cell Transplantation

Background: Persistent thrombocytopenia following allogeneic stem cell transplantation (alloHSCT) leads to an increase in morbidity and mortality. Causes of severe thrombocytopenia following HSCT include poor graft function, graft-versus-host disease (GVHD), infections, drug toxicities, underlying autoimmune diseases and relapse of underlying disease. Treatments can include thrombopoietin receptor agonists (TPO-RA), immunomodulators, and stem cell boost. Avatrombopag is a second generation TPO-RA approved for the treatment of primary chronic immune thrombocytopenia (ITP) in adult patients with poor response to standard treatments or in patients with chronic liver disease (CLD) associated thrombocytopenia requiring surgical interventions. Phase III clinical trials have shown greater platelet responses in chronic ITP and reduced transfusion needs in patients with CLD. Avatrombopag differs from other TPO-RA medications due to majority of elimination occurring in the gut, thus avoiding hepatic toxicity. Additionally, it does not require dietary restrictions. As there is limited literature in pediatric patients following alloHSCT, we describe the use of avatrombopag in a pediatric patient with chronic severe thrombocytopenia (&amp;lt;10 x10 3/uL) post HSCT. Objective: To describe the use of avatrombopag for severe refractory thrombocytopenia in a pediatric alloHSCT recipient. Case Presentation: We present a 14-year-old Hispanic male with Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ ALL) who received a maternal haploidentical HSCT with myeloablative conditioning and post-transplant cyclophosphamide. His post HSCT course was complicated by adenoviremia, hepatic variant GVHD, Enterobacter cloacae bacteremia and poor graft function. Seven months following HSCT, patient was found to be severely pancytopenic. Bone marrow morphology demonstrated 20-30% cellularity without evidence of leukemia relapse or GVHD. Lab evaluation was not consistent with transplant associated thrombotic microangiopathy. He received a stem cell boost for presumed poor graft function. Patient demonstrated partial response by resolution of neutropenia and anemia; however, severe thrombocytopenia persisted. Multiple bone marrow evaluations remained negative for disease with full donor chimerism and negative TCR clonality. CXCL9 was noted to be elevated at 4270 and Immature Platelet fraction was elevated at 8.8. Platelet antibodies remained negative and all findings consistent with persistent severe ITP. Multiple treatments including romiplostim; eltrombopag; high dose immune globulin (IVIG); rituximab; methylprednisolone; and decitabine were not successful in improving platelet count (Figure 1). Evaluation for severe thrombocytopenia remained negative. During the course of severe thrombocytopenia, patient required several hospitalizations for symptomatic thrombocytopenia, requiring multiple platelet transfusions. Due to the severity of disease, he was granted a compassionate use investigational new drug (IND 165837) for avatrombopag and began on day +332. Dosing was initiated at 20 mg daily with a dosage adjustment to achieve platelet recovery to &amp;gt;50 x10 3/uL free from transfusion. The dose was titrated per manufacturer to maximum dose of 40 mg daily with response to platelet count &amp;gt;100 x10 3/uL in approximately 6 weeks time. By three months of treatment, dose was titrated down 40 mg three times a week and 20 mg on alternating days. Patient continues to maintain platelets above 100 x10 3/uL with no medication toxicities or adverse events noted. Patient has been able to return to his pre-alloHSCT lifestyle including contact sports and re-immunizations.

Monoclonal and Oligoclonal Anti-RBC Antibodies Can Mediate Warm Autoimmune Hemolytic Anemia

Background: Recent data from the field of autoimmune platelet antibodies in vaccine-induced immune thrombotic thrombocytopenia (VITT) suggests that antibodies with restricted clonality may be associated with more severe outcomes. Warm autoimmune hemolytic anemia (WAIHA) is an IgG-mediated red blood cell (RBC) disorder. The goal of this study was to investigate the clonality of anti-RBC IgG antibodies in WAIHA, and to assess if clonal restriction was associated with more severe disease course and outcomes. Methods: 15 patients with WAIHA were evaluated. All patients had proven IgG positivity in direct antiglobulin testing (DAT, or “Coombs” test). RBC eluates were prepared and both the patient plasma sample, as well as the RBC eluate, were subject to liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF MS). Based on the number of antibodies seen in the RBC eluate, patients were classified into mono/oligoclonal vs. polyclonal antibody WAIHA groups Assessment of response to treatment was based on international consensus criteria: complete (CR; normal Hb or Hb ≥12 g/dL, with resolution of hemolysis); partial (PR; Hb &amp;gt;10 but &amp;lt;12 g/dL or Hgb &amp;gt;12 g/dL without resolution of hemolysis); or no response (neither CR nor PR). Results: Eleven of the 15 patients (73%) were found to have polyclonal antibodies, while four patients (27%) had mono/oligoclonal WAIHA antibodies. Of these four patients with restricted clonality, two patients had monoclonal antibodies (Figure 1 shows one of the monoclonal WAIHA antibodies identified). There was no significant difference in demographic composition, clinical findings, or treatment received in both groups (Table 1). 66.7% (n=10) of patients were male, and the mean age (SD) was 62.5 years (24.5). Two pediatric patients, ages 10 and 16, were included. Concomitant lymphoproliferative disease was present in 46.7% of the patients. The three most common treatments were steroids (100%), rituximab (93.3%), and splenectomy (13.3%). 40.0% of patients had died at the time of this analysis with no difference between the groups. The number of treatments received were similar between the mono/oligoclonal and polyclonal groups. After the first line of treatment, 100% and 77.8% of the mono/oligoclonal and polyclonal groups respectively achieved PR or CR (P=0.31). Additionally, 100% of the mono/oligoclonal group and 54.5% of the polyclonal group were in PR or CR by their most recent CBC (P=0.10). 50.0% and 54.5% of the mono/oligoclonal group and polyclonal groups respectively relapsed at least once (P=0.25). In those who relapsed, there was an average of 1.0 relapse events in the mono/oligoclonal group compared to 1.7 relapse events in the polyclonal group (P=0.32). Conclusion: This study demonstrates, for the first time, that monoclonal and oligoclonal antibodies can mediate warm autoimmune hemolytic anemia. While these data suggest no difference in clinical outcomes or disease course between patients with mono/oligoclonal vs. polyclonal anti-RBC antibodies, a key limitation is the small sample size.

Using immature platelet fraction as a factor in deciding on the need for platelet transfusions

Our study aimed to assess the prognostic significance of immature platelet fraction (IPF) and its role in deciding whether to transfuse platelets. The study was approved by the Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. We monitored this hematologic parameter in 6 patients before and after hematopoietic stem cell transplantation (HSCT). For the study, we used whole blood collected in K EDTA tubes. IPF levels were measured by flow cytometry on the automated hematology analyzer SYSMEX XE-2100 (Sysmex, Kobe, Japan). The presence of platelet antibodies was detected using Capture-P Ready-Screen solid phase system for the detection of antibodies to platelets and the NEO Blood Bank Analyzer by Immucor, Inc. It was shown that the use of IPF enabled an early establishment of platelet engraftment and helped to make more a reasoned decision regarding the transfusion of platelets. It was established that if a rise in IPF &gt; 6% was not accompanied by an increase in platelet count, serum platelet antibody testing was needed. IPF can help diagnose platelet engraftment failure following HSCT and thus eliminate the need for bone marrow aspiration. IPF is of great clinical importance; if adopted as a routine hematologic parameter, it can serve as an additional factor in deciding on the need for platelet transfusions and platelet antibody testing and subsequent personalized selection of platelets.

PB1395 Successful Management of Multiple Tooth Extraction in a Patient with Glanzmann Thrombasthenia with Platelet Antibodies

PB1395 Successful Management of Multiple Tooth Extraction in a Patient with Glanzmann Thrombasthenia with Platelet Antibodies

Pathogenesis of refractory ITP: Overview.

A subset of individuals with 'primary' or 'idiopathic' immune thrombocytopenia (ITP) who fail to respond to conventional first- and second-line agents or who lose responsiveness are considered to have 'refractory' disease (rITP), placing them at increased risk of bleeding and complications of intensive treatment. However, the criteria used to define the refractory state vary among studies, which complicates research and clinical investigation. Moreover, it is unclear whether rITP is simply 'more severe' ITP, or if there are specific pathogenic pathways that are more likely to result in refractory disease, and whether the presence or development of rITP can be established or anticipated based on these differences. This paper reviews potential biological features that may be associated with rITP, including genetic and epigenetic risk factors, dysregulation of T cells and cytokine networks, antibody affinity and specificity, activation of complement, impaired platelet production and alterations in platelet viability and clearance. These findings indicate the need for longitudinal studies using novel clinically available methodologies to identify and monitor pathogenic T cells, platelet antibodies and other clues to the development of refractory disease.

Pregnant Women at Low Risk of Having a Child with Fetal and Neonatal Alloimmune Thrombocytopenia Do Not Require Treatment with Intravenous Immunoglobulin.

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare condition in which maternal alloantibodies to fetal platelets cause fetal thrombocytopenia that may lead to intracranial hemorrhage (ICH). Off-label intravenous immunoglobulin (IVIg) has for 30 years been the standard of care for pregnant women who previously have had a child with FNAIT. The efficacy of this treatment has never been tested in a placebo-controlled clinical trial. Although IVIg treatment may improve the neonatal outcome in women who previously have had a child with FNAIT-associated ICH, the question is whether IVIg is necessary for all immunized pregnant women at risk of having a child with FNAIT. The results from some recent publications suggest that antenatal IVIg treatment is not necessary for women who are (1) HPA-1a-immunized and HLA-DRB3*01:01-negative, (2) HPA-1a-immunized with a previous child with FNAIT but without ICH or (3) HPA-5b-immunized. If IVIg is not used for these categories of pregnant women, the amount of IVIg used in pregnant women with platelet antibodies would be reduced to less than ¼ of today's use. This is important because IVIg is a scarce resource, and the collection of plasma for the treatment of one pregnant woman is not only extremely expensive but also requires tremendous donor efforts.

Pseudothrombocytopenia, beyond a laboratory phenomenon: study of 192 cases

The platelet antibodies that cause pseudothrombocytopenia (PTCP) act only in vitro and do not produce clinical bleeding. Most studies on PTCP have focused on improving differential diagnosis with true thrombocytopenia but studies on the characteristics of patients with PTCP are limited. In this study, we aimed to evaluate the clinical and biological characteristics of 192 patients with PTCP. In addition to general variables, we evaluated automated and microscopic platelet counts, platelet clumps, platelet diameters, immature platelet fraction (IPF), and platelet antibodies. Adult women accounted for the largest subgroup of patients (n=82; 42.7%) and 67 patients (34.9%) were grouped into families. Forty-four patients (22.9%) had one or more associated autoimmune disorders (ADs); 39 relatives of these patients (19.8%) had ADs and 45 relatives (23.4%) had immune thrombocytopenia (ITP) or unspecified thrombocytopenia. Platelet cryptantibodies and/or autoantibodies were positive in 56 patients (30.1%). Most patients (n=169; 80%) had automated platelet counts >80×109/L. In all patients, microscopic platelet counts were ≥150×109/L. The platelet clump index (% increase in microscopic platelet count compared to automatic count) ranged from 30 to >7000%. Platelet diameters and IPF parameters were significantly greater in the PTCP versus healthy controls (p<0.001). A total of 17 patients (8.8%) had had previous ITP or the PTCP evolved into ITP. Our data suggest that PTCP should be considered a situation of autoimmunity; the assessment of platelet clumps has a high diagnostic value; the close association between ITP and PTCP suggests that these conditions could be different phases of the same process.

The interplay between GPIb/IX antibodies, platelet hepatic sequestration, and TPO levels in patients with chronic ITP.

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder with an incompletely understood pathophysiology but includes platelet-clearance in the spleen and liver via T cells and/or platelet autoantibodies. Strikingly, thrombopoietin (TPO) levels remain low in ITP. Platelet-glycoprotein (GP)Ibα has been described to be required for hepatic TPO generation; however, the role of GPIb antibodies in relation to platelet hepatic sequestration and TPO levels, with consideration of platelet counts, remains to be elucidated. Therefore, we examined 53 patients with chronic and nonsplenectomized ITP for whom we conducted indium-labeled autologous platelet scintigraphy and measured platelet antibodies and TPO levels. Upon stratification toward the severity of thrombocytopenia, no negative association was observed between GPIb/IX antibodies and TPO levels, suggesting that GPIb/IX antibodies do not inhibit or block TPO levels. Surprisingly, we observed a positive association between GPIb/IX antibody levels and TPO levels and GPIb/IX antibodies and platelet hepatic sequestration in patients with severe, but not mild or moderate, thrombocytopenia. In addition, platelet hepatic sequestration and TPO levels were positively associated. This collectively indicates that GPIb/IX antibodies may be associated with increased platelet hepatic sequestration and elevated TPO levels in patients with severe thrombocytopenic ITP; however, further research is warranted to elucidate the pathophysiologic mechanisms.

Deteksi Antibody Anti-Human Leukocyte Antigen (HLA) Kelas I Pada Donor Darah Wanita

Background: HLA class I is very polymorphic, if it enters the body of another person it will be considered foreign so that alloimmunization can occur by producing class I anti-HLA antibodies. These antibodies are found in individuals exposed to allogeneic cells due to transfusion, problems, and pregnancy. Female blood donors who have anti-HLA class I antibodies when donating blood and transfused to patients who have the appropriate HLA can cause a transfusion reaction. Research on class I anti-HLA antibodies in female blood donors in Indonesia is still very rare. This research is further to get an overview of class I anti-HLA antibodies in female blood donors.Objective: To determine the presence of potential class I anti-HLA antibodies in female donors.Methods: The subjects of this study were 30 female donors who had never been pregnant and 60 donors who had been pregnant and gave birth who donated their blood at UTD PMI DKI Jakarta. The collected samples were screened using the whole platelet ELISA method to detect platelet antibodies, namely anti-HPA and anti-HLA class I antibodies, followed by consulting anti-HLA class I antibodies with the MAIPA method.Results: Sixteen samples were detected to contain anti-platelet antibodies and 74 were negative. Identification of class I anti-HLA antibodies in 16 samples showed all negative results.Conclusion: Identification of 16 positive anti-platelet antibody samples in female donors did not show class I anti-HLA antibodies

Therapeutic Efficacy of Platelet Transfusion and Analysis of Influencing Factors in 364 patients

Introduction: The aims of this study were to observe the therapeutic effect of platelet (PLT) transfusion and to analyze influencing factors for the sake of providing useful clues for improving the efficacy of PLT transfusion. Methods: Included in this study were patients who received PLT transfusion in the affiliated hospital of Nantong University. Patients’ sex, age, height, weight, PLT transfusion status, and 20–24-h PLT count before and after PLT transfusion were collected to calculate the PLT corrected count increment values before and after PLT transfusion. Solid-phase red cell adherence assay was used to determine PLT antibody. Statistical analysis was performed using SPSS25.0 Software. Results: A total of 364 patients received 1,060 PLT transfusions, including 728 successful transfusions and 332 unsuccessful transfusions. When the patients were grouped according to different etiologies, significant differences in PLT transfusion effectiveness were observed between these groups (χ² = 15.070, p < 0.05). Grouping of the 364 patients according to sex, blood type, and PLT transfusion frequency showed no significant difference in PLT transfusion refractoriness (PTR) between different age-groups and sexes (p > 0.05). With the number of PLT transfusions increasing, PTR increased gradually. PLT antibodies were detected of 364 patients, 67 of them were positive. Among them, 63 cases (94.02%) were positive for HLA class I antibody. Conclusion: To reduce PTR, multiple factors should be considered comprehensively when PLT transfusion therapy is to be implemented in clinical practice. PLT antibody is the main immune factor causing PTR.

Platelet function and soluble P-selectin in patients with primary immune thrombocytopenia

BackgroundThe bleeding phenotype in immune thrombocytopenia (ITP) is heterogeneous, but usually mild and only partly dependent on the severity of thrombocytopenia. Platelet reactivity has previously been suggested to underly the mild phenotype. MethodsPlatelet function was assessed as basal and agonist-induced surface expression of P-selectin and activation of GPIIb/IIIa via flow cytometry, and soluble (s)P-selectin levels were assessed in plasma of 77 patients with primary ITP, 19 hemato-oncologic thrombocytopenic controls (TC) and 20 healthy controls (HC). The association of platelet function with laboratory and clinical parameters such as bleeding manifestations at inclusion and previous thrombosis was analyzed. ResultsITP patients showed tendency towards increased surface P-selectin and elevated levels of activated GPIIb/IIIa. Platelet activation after stimulation with all agonists including TRAP-6, ADP, arachidonic acid and CRP was decreased compared to HC. Compared to TC, only GPIIb/IIIa activation but not surface P-selectin was higher in ITP. Levels of soluble (s)P-selectin were significantly higher in ITP patients compared to TC, but similar to HC. Higher sP-selectin levels were associated with blood group O and current therapy, with highest levels in TPO-RA treated patients. Platelet reactivity was not associated with platelet count or size, platelet antibodies, treatment regime, or blood group. No correlation between platelet activation with the bleeding phenotype or previous thrombotic events could be observed. ConclusionITP patients did not have hyper-reactive platelets compared to HC, but partly higher reactivity compared to TC. Further studies are needed to understand the underlying mechanism behind the bleeding and pro-thrombotic phenotype in ITP.250/250.