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Cardiopulmonary bypass surgery (CPB) is associated with a high incidence of IgG Abs against platelet factor 4/heparin (PF4/H) complexes by day 6 after surgery. These Abs are associated with an immune-mediated adverse drug reaction, heparin-induced thrombocytopenia. Although the early onset of the anti-PF4/H IgG response is compatible with a secondary immune response, the rapid decline of Ab titers thereafter is not. To shed light on the origin of these Abs, in the present study, we prospectively compared the kinetics of these Abs with that of Abs against 2 recall Ags and to that of autoantibodies in 166 CPB patients over 4 months. Surgery induced strong inflammation, as shown by an increase in mean C-reactive protein levels. Consistent with previous studies, anti-PF4/H IgG optical density transiently increased between baseline and day 10 (P < .001; not associated with C-reactive protein levels), followed by a decrease over the next months. In contrast, concentrations of antidiphtheria toxin IgG and antitetanus toxin IgG increased constantly over the 4 months after surgery by 25%-30%. IgG autoantibodies did not change. Therefore, the transient kinetics of the anti-PF4/H IgG response resembled neither that of recall Abs nor that of IgG autoantibodies, but rather showed a unique profile.

Purpose of Review: The purpose of the review is to show the similarities between haemolytic disease of the foetus and newborn (HDFN) and foetal and neonatal alloimmune thrombocytopenia (FNAIT) and to describe the background and challenges related to the current endeavours of developing a prophylaxis against FNAIT. The rationale for this prophylaxis is similar to the prophylaxis which has been used with great success for the last 40 years against RhD-associated HDFN. The idea is to prevent human platelet antigen (HPA)-1a-associated FNAIT by administering anti-HPA-1a immunoglobulin G (IgG) to nonimmunized HPA-1a-negative women after delivery of an HPA-1a-positive child., Recent Findings: Results from a Norwegian screening and intervention study on FNAIT have indicated that about 75% of women with antibodies against HPA-1a are immunized in relation to delivery. This observation leads to the possibility of preventing HPA-1a-associated FNAIT in the same way as today's prevention of HDFN. Results from a proof-of-concept study in a murine FNAIT model have shown that the production of alloantibodies against platelets can be suppressed by administrating antiplatelet antibodies after the antigenic challenge. Even more interesting, the prophylactic antiplatelet antibodies could also significantly reduce the clinical consequences of FNAIT in this FNAIT model., Summary: These novel observations have paved the way for clinical studies. Production and testing of anti-HPA-1a IgG for clinical use will be carried out by a European Union-funded consortium. If the results from the clinical trial are favourable, there is a chance that a medicinal product for the prevention of FNAIT will be available within this decade.

Background: The use of crossmatch-compatible platelets (PLTs) improves posttransfusion corrected count increments (CCIs) in patients with alloimmune PLT refractoriness. However, few reports address the efficacy of utilizing this strategy for patients requiring intensive PLT transfusion therapy lasting several weeks to months., Study Design and Methods: Medical records of patients with two or more PLT crossmatch assays performed between 2002 and 2010 were reviewed. All patients were refractory to random single-donor apheresis PLT units, defined as two consecutive 1-hour posttransfusion CCIs of less than 7500. A commercial solid-phase adherence assay was used for crossmatching., Results: Seventy-one patients were included. A median of four crossmatch assays were performed per patient (range, 2-17). Mean percent reactivity in initial (58.6%) versus last (55.3%) crossmatch assay for each patient demonstrated no trend toward progressive alloimmunization (p = NS). A total of 738 crossmatched PLT units were administered with a mean ± standard deviation CCI of 7000 ± 7900 (n = 443 units with adequate 1-hr posttransfusion counts), a significant improvement over random PLTs (p < 0.001). Patients with an initial crossmatch reactivity of greater than 66% were significantly more likely to demonstrate at least one panreactive crossmatch assay, impacting the availability of compatible PLTs for optimum transfusion support. One patient (1.4%) developed WHO Grade IV bleeding., Conclusions: Progressive alloimmunization to mismatched antigens does not impact medium-term transfusion support with crossmatched PLTs. Increased reactivity in the initial crossmatch assay can serve as a trigger to initiate workup for HLA-matched PLTs as a second-line approach. However, for most patients, medium-term transfusion support with crossmatched PLTs offers an effective and rapid first-line approach to management of PLT transfusion refractoriness., (© 2012 American Association of Blood Banks.)

Unlabelled: Foetal and neonatal alloimmune thrombocytopenia (FNAIT) and neonatal neutropenia caused by maternal autoantibodies against neutrophils are rare disorders. We describe a newborn with severe thrombocytopenia and intracerebral bleeding caused by maternal anti-HPA-3a alloantibodies and mild neutropenia caused by maternal autoantibodies against HNA-1b. This appears to be the first case of simultaneous occurrence of these two conditions., Conclusion: This case report and review of the literature demonstrate that anti-HPA-3a antibodies can be overlooked by standard assays., (© 2012 The Author(s)/Acta Paediatrica © 2012 Foundation Acta Paediatrica.)

Background: Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a severe bleeding disorder caused by maternal antibody-mediated destruction of fetal or neonatal platelets (PLTs). Results from our recent large screening study suggest that the pathophysiology of FNAIT is more similar to hemolytic disease of the fetus and newborn (HDFN) than previously thought. Immunization against HPA-1a might therefore be preventable by a prophylactic regimen of inducing antibody-mediated immune suppression (AMIS), which has been documented to be a useful prophylaxis against HDFN. This preclinical proof-of-concept study investigated whether passive administration of anti-β3 integrin could induce AMIS and thereby prevent clinical complications of FNAIT., Study Design and Methods: A murine model of FNAIT using β3 integrin (GPIIIa)-deficient (β3-/-) mice was employed for this study. AMIS in β3-/- mice was induced by intravenous administration of human anti-HPA-1a immunoglobulin G or murine anti-β3 antisera given as prophylaxis after transfusion of HPA-1a-positive human PLTs or murine wild-type PLTs, respectively., Results: AMIS against both human and murine PLT antigens was induced using this prophylactic approach, reducing the amount of maternal PLT antibodies by up to 90%. Neonatal PLT counts were significantly increased and pregnancy outcome was improved in a dose-dependent manner. The incidence of intracranial hemorrhage, miscarriage, and dead-born pups in mice receiving high-dose prophylaxis was reduced to that of normal controls. We also observed that the severity of thrombocytopenia inversely correlated with birth weight., Conclusion: This work conceptually proves that prophylactic administration of PLT antibodies induces AMIS and prevents poor pregnancy outcome in FNAIT., (© 2012 American Association of Blood Banks.)

Background: Neonatal alloimmune thrombocytopenia (NAIT) is a disorder characterized by maternal alloimmunization against paternal fetal platelet antigens. Two healthy, unrelated Japanese women each gave birth to a child with severe NAIT., Study Design and Methods: To elucidate the maternal causes of NAIT, we conducted serologic and genetic studies in these two NAIT infants., Results: The serologic experiments localized the antigens to the glycoprotein (GP) IIIa subunit of the GPIIb/IIIa complex. Sequence-based typing studies subsequently identified a G>A mutation at Nucleotide 1960 (a glutamic acid > lysine substitution at Position 628) in the 11th exon of the GPIIIa gene. This mutation was recently identified in a report as HPA-21bw. Next, it was determined that the cause of NAIT in both cases was the HPA-21bw antigen, as shown by the mothers' antibodies reacting with the mutated GPIIIa-transfected cells, but not with transfectants expressing wild-type GPIIIa. A molecular genetic screening for the HPA-21bw allele among Japanese donors showed that its genetic frequency in the population was 0.53% (10/1888), indicating that HPA-21bw occurs at a low but appreciable frequency in the population. Furthermore, in a retrospective study of 50 previous NAIT cases of unknown causes, we found one NAIT case associated with the HPA-21bw antibody. The two NAIT cases in this study represent the first ones to be associated with HPA-21bw in Japan., Conclusion: We identified the HPA-21bw allele from two unrelated Japanese infants with severe NAIT. We identified 10 individuals (1.06%) positive for the HPA-21bw allele from a genetic screening of 944 Japanese blood donors., (© 2011 American Association of Blood Banks.)

Background: Maternal immunization against low-frequency, platelet (PLT)-specific antigens is being recognized with increasing frequency as a cause of neonatal alloimmune thrombocytopenia (NAIT)., Study Design and Methods: Serologic and molecular studies were performed on PLTs and DNA from two families in which an infant was born with severe thrombocytopenia not attributable to maternal immunization against known PLT-specific alloantigens., Results: Antibodies reactive only with paternal PLTs were identified in each mother using flow cytometry and solid-phase assays. Unique mutations encoding amino acid substitutions K164T in glycoprotein (GP)IIb (Case 1) and R622W in GPIIIa (Case 2) were identified in paternal DNA and in DNA from the affected infants. Each maternal antibody recognized recombinant GPIIb/IIIa mutated to contain the polymorphisms identified in the corresponding father. None of 100 unselected normal subjects possessed these paternal mutations., Conclusions: Severe NAIT observed in the affected infants was caused by maternal immunization against previously unrecognized, low-frequency antigens created by amino acid substitutions in GPIIb/IIIa (α(IIb) /β(3) integrin). A search should be conducted for novel paternal antigens in cases of apparent NAIT not explained on the basis of maternal-fetal incompatibility for known human PLT antigens., (© 2011 American Association of Blood Banks.)

Background: Neonatal alloimmune thrombocytopenia is mostly due to the presence of maternal antibodies against the fetal platelet antigen HPA-1a on the platelet integrin GPIIb-IIIa. Accurate detection of anti-HPA-1a antibodies in the mother is, therefore, critical. Current diagnostic assays rely on the availability of pools of human platelets that vary according to donors and blood centers. There is still no satisfactory standardization of these assays., Design and Methods: Peptide aptamer was used to detect and identify HPA-1a-specific antibodies in human serum that do not require human platelets. A peptide aptamer library was screened using an anti-HPA-1a human monoclonal antibody as a bait to isolate an aptamer that mimics the human platelet antigen HPA-1a., Results: This is the first report in platelet immunology of the use of a peptide aptamer for diagnostic purposes. This assay gives better results than the MAIPA currently in use, detecting around 90% of the expected alloantibodies., Conclusions: This assay could help define a standard for the quantitation of anti-HPA antibodies. This report also demonstrates that peptide aptamers can potentially detect a variety of biomarkers in body fluids; this is of particular interest for diagnostic purposes.

A single nucleotide polymorphism in the integrin α2 gene ITGA2 (rs1801106; G1600A) creates the non-conservative amino acid substitution E534K, the basis of the human platelet alloantigen system HPA-5. Yet HPA-5 alleles do not influence binding of α2β1 to its primary ligand collagen I, and the effect of HPA-5 on platelet function has not been determined. We used a direct platelet adhesion assay to evaluate whether differential inheritance of HPA-5 alleles influences platelet adhesion to collagen I or an alternative ligand, decorin. Platelets from donors bearing one or more minor allele HPA-5b showed attenuated adhesion to purified decorin but not collagen I. Adhesion to decorin was significantly inhibited by human alloantibodies specific for HPA-5a but not by the collagen I sequence GFOGER or α2-specific inhibitory monoclonal antibodies. The minor allele 534K attenuates platelet adhesion to decorin but not collagen I, providing the first evidence of a functional effect of HPA-5 alleles.

Background: Our blood bank prepares, on indication or request, a volume-reduced (VR) platelet (PLT) product with greater than 95% reduced plasma content and a 15-fold higher PLT concentration, potentially minimizing adverse reactions due to plasma, in particular for human leukocyte antigen (HLA)/human PLT antigen (HPA)-matched PLTs when minor ABO incompatibility cannot be avoided. Here we compared the clinical effectiveness of VR apheresis PLTs (APs) with standard APs., Study Design and Methods: We performed a single-center cohort study among consecutive alloimmunized patients who received either HLA/HPA-matched standard APs and/or VR-APs between 1994 and 2008. The endpoints were corrected count increments (CCIs), time to next transfusion, and frequency of adverse reactions. The CCI of VR PLTs was calculated using the PLT dose before volume reduction. Using a random effects model, 851 transfusions to 68 patients were evaluated for CCI and 731 transfusions to 64 patients for time to next transfusion. The frequency of reported adverse reactions was compared between the groups., Results: The 1-hour CCI was 23% (95% confidence interval [CI], 9%-42%; p < 0.001) lower and the 24-hour CCI was 17% (95% CI, -11% to 59%; p = 0.278) lower after VR-APs. The mean time to next transfusion was similar: standard APs, 3.1 days (95% CI, 2.7-3.5); and VR-APs, 2.8 days (95% CI, 2.5-3.2). Eight adverse reactions were reported: 4 of 619 in the standard AP group and 4 of 1202 in the VR-AP group., Conclusion: VR-APs showed lower 1- and 24-hour CCIs than standard-APs, which can be largely explained by the lower PLT dose of VR-APs. The benefits of plasma reduction should seriously be outweighed given these lower increments., (© 2011 American Association of Blood Banks.)

Introduction: The HPA-15 antigen system is characterized by a low antigen expression on platelets. The antibodies against this antigen are implied in fetal/neonatal alloimmune thrombocytopenia (F/NAIT), post-transfusion purpura, and refractoriness to platelet transfusions. Detection of these antibodies appears to be related to the level of HPA-15 expression on the platelets used in the monoclonal antibody-specific immobilization of platelet antigen (MAIPA) assay., Methods: We performed genotyping of 300 healthy blood donors for HPA-15 by TaqMan real-time PCR technology, and the HPA-15 antigen expression was investigated in 13 HPA-15aa and 19 HPA-15bb individuals. We also investigated the relevance of HPA-15 antigen expression on donor platelets used in MAIPA for antibody detection in 223 multitransfused hematological patients and 271 women with suspected F/NAIT., Results: In Polish donors, the HPA-15a allele frequencies were lower than the HPA-15b (0.480 vs. 0.515). We identified three HPA-15 expression groups: high (36.7 ± 8.36 MFI - eight cases), medium (19.5 ± 6.2 MFI - 21 cases), and low (6.5 ± 5.9 MFI - three cases). The HPA-15 expression was stable over time. The HPA-15aa and HPA-15bb platelets with high antigen expression were used for anti-HPA-15 antibody detection; anti-HPA-15 antibodies were detected in 4/223 (1.8%) patients receiving multiple transfusions but in none of the 271 women with suspected F/NAIT. Further examination of the four sera by MAIPA with various platelets revealed the optical density in the assay to be closely related to the level of HPA-15 antigen expression., Conclusion: Anti-HPA-15 antibody detection should be based on carefully selected platelets with high HPA-15 expression level., (© 2011 Blackwell Publishing Ltd.)

Objective: To develop a reliable preimplantation genetic diagnosis protocol for antihuman platelet antigen-1 incompatibility for a family in whom antenatal treatment was not possible because of the mother's hypersensitivity to intravenous immunoglobulin (IVIG)., Methods: Haplotypes were constructed from genomic DNA of the family members. A polymerase chain reaction protocol that included eight microsatellite polymorphic markers and the ITGB3-specific (T196C, rs5918) polymorphism were multiplexed to be used in a single cell protocol, and single blastomeres were analyzed., Results: In one preimplantation genetic diagnosis cycle, out of 28 retrieved oocytes, 24 embryos fertilized and 12 underwent biopsy. Three embryos were found to be antihuman platelet antigen-1b/1b homozygotes and two were transferred. This cycle resulted in an uneventful pregnancy and birth of a healthy child., Conclusion: In cases in which there is antihuman platelet antigen incompatibility and IVIG cannot be administered, preimplantation genetic diagnosis is a reliable alternative to enable birth of unaffected children.

Background: The HPA-1a (Leu(33)) polymorphism of platelet integrin αIIbβ3 is the target of alloantibodies in 70-80% cases of neonatal alloimmune thrombocytopenia (NAIT) in Caucasians and reliable detection of these antibodies is essential for appropriate clinical management. However, the ability to detect such antibodies is highly variable between laboratories and, in a number of clinical cases where there is a HPA-1 genotype mismatch between mother and neonate, HPA-1a antibodies are undetectable. Furthermore, some studies have not shown a consistent relationship between maternal anti-HPA-1a level and neonatal platelet count. Since the integrity and conformation of the αIIbβ3 complex are dependent on divalent cations, we investigated whether HPA-1a epitope integrity and/or conformation might be affected by the presence of the cation chelator EDTA in patient samples or in assay buffers, thus providing a possible explanation for the variable sensitivity of current assays., Principle Findings: Exposure of the αIIbβ3 complex to EDTA resulted in reduced reactivity of three anti-HPA-1a mAbs (B2, 19-7 and 23-15). More significantly, cation chelation adversely affected detection of polyclonal anti-HPA-1a, not only in the platelet immunofluorescence assay, where alloantibody binding was reduced compared to control platelets (mean MFI reduction 44.5%, range 17.3-69.7%, n=4), but also in the commonly used monoclonal antibody specific immobilisation of platelet antigens assay (MAIPA) where both alloantibody and monoclonal capture antibody binding were reduced (mean OD reduction 82.8%, range 68.3-96.6%, n=9)., Conclusions: These data show that HPA-1a antibodies recognise epitopes on αIIbβ3 that are sensitive to EDTA treatment and that cation chelation grossly reduces the sensitivity of the MAIPA assay by diminishing not only HPA-1a alloantibody binding but also 'capture' monoclonal antibody binding. These findings may, in part, explain the current variability in antibody measurement and will guide the development of more sensitive tests for anti-integrin antibodies in NAIT and other conditions., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Objective: To assess whether maternal HPA 1a alloimmunization is associated with birthweight., Design: A retrospective observational cohort study., Setting: The national reference laboratory for clinical platelet immunology at a university hospital., Population: 165 HPA 1a incompatible pregnancies identified from a recent screening study of 100 448 women (124 pregnancies) and the national reference laboratory for clinical platelet immunology (41 pregnancies)., Methods: A linear mixed model analysis was used to assess whether maternal anti-HPA 1a antibodies were associated with birthweight. A generalized linear model was used to assess maternal anti-HPA 1a antibodies as risk factor for small-for-gestational age neonates. Both models were adjusted for gestational age at time of delivery, maternal age, parity, smoking habits during pregnancy, preeclampsia, diabetes mellitus and fetal sex. MAIN OUTCOME MEASURES. Maternal anti-HPA 1a antibody as risk factor of reduced birthweight and small-for-gestational age neonates., Results: The level of maternal anti-HPA 1a antibodies was significantly associated with birthweight and risk of small-for-gestational age neonates after correcting for confounding variables (p<0.001). However, this association was only significant for boys. When the mother had high levels of anti-HPA 1a antibodies during pregnancy, the adjusted mean birthweight in boys was 530g lower compared with anti-HPA 1a antibody negative pregnancies (p<0.001)., Conclusions: A linear relation between maternal anti-HPA 1a antibody levels and reduced birthweight in boys was demonstrated. Reduced birthweight should be considered a possible complication of fetal and neonatal alloimmune thrombocytopenia., (© 2011 The Authors Acta Obstetricia et Gynecologica Scandinavica © 2011 Nordic Federation of Societies of Obstetrics and Gynecology.)

Background: Maternal alloantibodies against HPA-1a can cross placenta, opsonize foetal platelets, and induce neonatal alloimmune thrombocytopenia (NAIT). In a study of 100, 448 pregnant women in Norway during 1995-2004, 10.6% of HPA-1a negative women had detectable anti-HPA-1a antibodies., Design and Methods: A possible correlation between the maternal ABO blood group phenotype, or underlying genotype, and severe thrombocytopenia in the newborn was investigated., Results: We observed that immunized women with blood group O had a lower risk of having a child with severe NAIT than women with group A; 20% with blood group O gave birth to children with severe NAIT, compared to 47% among the blood group A mothers (relative risk 0.43; 95% CI 0.25-0.75)., Conclusion: The risk of severe neonatal alloimmune thrombocytopenia due to anti-HPA-1a antibodies is correlated to maternal ABO types, and this study indicates that the observation is due to genetic properties on the maternal side.

Background: Neonatal alloimmune thrombocytopenia (NAIT) is mostly caused by maternal antibodies against human platelet antigen 1a (HPA-1a) expressed on glycoprotein (GP) IIb/IIIa. Accumulated evidence indicated that anti-HPA-1a could be overlooked by standard methods due to low avidity. Low-avidity HPA-1a antibodies were shown to be detectable by surface plasmon resonance (SPR). We sought to investigate the frequency and in vivo relevance of low-avidity anti-HPA-1a., Study Design and Methods: A retrospective cohort consisting of 82 HPA-1bb mothers of HPA-1ab newborns with thrombocytopenia was analyzed using standard serologic methods. Maternal immunoglobulin (Ig)G fractions were investigated for low-avidity antibodies in SPR using purified GPIIb/IIIa (HPA-1a or -1b). The capability of HPA-1a antibodies to clear platelets (PLTs) in vivo was analyzed using the NOD/SCID mouse model of alloimmune thrombocytopenia., Results: HPA antibodies were detectable in sera from 68 of 82 (83%) mothers using standard serologic methods and undetectable in 14 of 82 sera. In SPR, IgG fractions of sera reacting positive in monoclonal antibody immobilization of PLT antigen (MAIPA) assay showed specific binding to an HPA-1a flow cell (mean, 87 ± 21 resonance units [RU]). When MAIPA-negative sera were tested in SPR, binding with low avidity was observed in 7 of 14 to HPA-1a (mean, 31 ± 5 RU), but not to HPA-1b flow cell (mean, 5 ± 2 RU). In vivo, low-avidity antibodies were capable of clearing HPA-1ab PLTs but not HPA-1bb PLTs in a NOD/SCID mouse model. Elimination kinetics were slower than observed with MAIPA-positive antibodies., Conclusions: Low-avidity HPA-1a antibodies are present in a significant number of NAIT cases and, although they can escape detection by standard serology, they harbor the capability of PLT destruction in vivo., (© 2011 American Association of Blood Banks.)

We describe a reliable noninvasive fetal human platelet antigen (HPA)-1a genotyping assay on a real-time polymerase chain reaction (PCR) platform using cell-free fetal DNA isolated from maternal blood. Nonspecific amplification of maternal cell-free DNA is overcome by pre-PCR digestion of the cell-free DNA with the Msp1 restriction enzyme. Noninvasive fetal HPA-1a genotyping offers a safe method for alloimmunised pregnant women to determine whether their fetus is at risk of fetal or neonatal alloimmune thrombocytopenia (FNAIT) and whether interventions to prevent intracranial haemorrhage are required. The availability of this test is relevant to the ongoing debate on screening pregnancies for HPA-1a-mediated FNAIT., (© 2011 The Authors BJOG An International Journal of Obstetrics and Gynaecology © 2011 RCOG.)

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is caused by maternal antibodies that cross the placenta in connection with pregnancy and destroy fetal platelets. Recently, maternal T cell responses associated with FNAIT have been studied at the clonal level. These T cell clones recognize an integrin β3 epitope, which is anchored to the HLA-DRB3∗0101-encoded MHC molecule DR52a. The same MHC allele is strongly associated with FNAIT. As the production of pathological antibodies reactive with fetal platelets is likely dependent on these T cell responses, there exists a potential for preventing FNAIT by targeting these T cells., (Copyright © 2011. Published by Elsevier Ltd.)

Background: Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a bleeding disorder caused by transplacental passage of maternal antibodies to fetuses whose platelets (PLTs) express the corresponding human PLT antigen (HPA)., Study Designs and Methods: We observed a fetus with FNAIT who died from a severe intracranial hemorrhage. Analysis of maternal serum in antigen capture assay with paternal PLTs showed reactivity with PLT glycoprotein (GP)IIb/IIIa (α(IIb) β(3) ) and GPIa/IIa (α(2) β(1) integrin), indicating the presence of anti-HPA-1a and an additional alloantibody against GPIa (termed anti-Swi(a) )., Results: By immunochemical studies, the localization of the Swi(a) antigen on GPIa/IIa could be confirmed. Analysis of paternal GPIa full-length cDNA showed a single-nucleotide substitution C(3347) T in Exon 28 resulting in a Thr(1087) Met amino acid substitution. Testing of family members by polymerase chain reaction-restriction fragment length polymorphism using MslI endonuclease showed perfect correlation with phenotyping. Extended family and population studies showed that 4 of 10 members of the paternal family but none of 500 unrelated blood donors were Swi(a) carriers. Expression studies on allele-specific transfected Chinese hamster ovary (CHO) cells confirmed that the single-amino-acid substitution Thr(1087) Met was responsible for the formation of the Swi(a) epitope. Adhesion of CHO cells expressing the Swi(a) alloantigen to immobilized collagens was not impaired compared to the wild-type control and was not inhibited by anti-Swi(a) alloantibodies., Conclusion: In this study we defined a new PLT alloantigen Swi(a) that was involved in a case of additional immunization against HPA-1a. Our observations demonstrate that combinations of PLT-specific alloantibodies may comprise low-frequency alloantigens., (© 2011 American Association of Blood Banks.)

Objective: To optimize thrombocyte antibodies examination in pregnant and postpartum women., Design: Retrospective analysis., Setting: Blood Center, Faculty Hospital and Medical Faculty Ostrava University, Ostrava., Methods: Analysis and our experience with introducing the new test for thrombocyte antibodies examination., Conclusion: The thrombocyte antibodies examination that was introduce in the period 2008-2009 and is the combination of basic and special testing, seems to be optimal for the neonatal thrombocytopenia detection.

Fetomaternal or neonatal alloimmune thrombocytopenia (NAIT) is a rare but serious condition associated with significant fetal and neonatal morbidity and mortality. The most useful predictor of severe disease is a history of a sibling with an antenatal intracranial haemorrhage. However, NAIT can occur during the first pregnancy and may not be diagnosed until the neonatal period. Antenatal treatment options include maternal intravenous immunoglobulin (IVIG) and corticosteroid treatment, fetal blood sampling (FBS) and intrauterine platelet transfusion (IUT) and early delivery. FBS (with or without IUT) can be used to direct and monitor response to therapy, and to inform mode and timing of delivery. However, this procedure is associated with significant risks, including fetal death, and is generally now reserved for high-risk pregnancies. This review highlights the current understanding of the epidemiology and pathophysiology of NAIT and summarises current approaches to investigation and management. It also introduces the newly established Australian NAIT registry. Owing to the relative rarity of NAIT, accruing sufficient patient numbers for studies and clinical trials at an institutional level is difficult. This national registry will provide an opportunity to collect valuable information and inform future research on this condition., (© 2011 The Authors. Australian and New Zealand Journal of Obstetrics and Gynaecology © 2011 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists.)

Background: Testing for alloantibodies against human platelet antigens (HPAs) is essential for the clinical diagnosis of fetomaternal alloimmune thrombocytopenia (FMAIT), posttransfusion purpura, and platelet (PLT) refractoriness. Most of the methods currently used for HPA alloantibody detection rely on the availability of panels of HPA-typed PLTs and some rely on validated monoclonal antibodies (MoAbs) against the PLT glycoproteins. Recombinant β3 integrins displaying the HPA-1a (rHPA-1a) or HPA-1b (rHPA-1b) epitopes have been produced as an alternative source of antigen. The suitability of these integrin fragments was evaluated for the development of an HPA-1a alloantibody screening assay, using Luminex xMAP technology., Study Design and Methods: A 3-plex bead assay was developed by coupling biotinylated rHPA-1a, rHPA-1b, and recombinant glycoprotein VI to LumAvidin microspheres. Forty patient samples referred for FMAIT diagnostic testing, which were previously screened by the MoAb-specific immobilization of PLT antigens (MAIPA) assay, were used to assess the assay., Results: The rHPA-1a- and rHPA-1b-coupled beads were able to detect HPA-1a and HPA-1b alloantibodies in all patient samples tested that were previously confirmed to contain HPA-1-specific antibodies. Furthermore, HLA Class I antibodies did not cross-react with the coupled beads., Conclusion: The 3-plex bead assay can be used to detect HPA-1a antibodies with sufficient specificity and sensitivity for use in the clinical setting of FMAIT. The development of other recombinant integrin fragments with the use of Luminex xMAP technology may assist in providing more rapid HPA antibody detection, enabling prompt diagnosis of alloimmune PLT disorders., (© 2010 American Association of Blood Banks.)

Background: Fetomaternal alloimmune thrombocytopenia results from the formation of antibodies by the mother which are directed against a fetal platelet alloantigen inherited from the father. The resulting fetal thrombocytopenia (reduced platelet numbers) may cause bleeding, particularly into the brain, before or shortly after birth. Antenatal treatment of fetomaternal alloimmune thrombocytopenia includes the administration of intravenous immunoglobulin (IVIG) and/or corticosteroids to the mother to prevent severe fetal thrombocytopenia. IVIG and corticosteroids both have short-term and possibly long-term side effects. IVIG is also costly and optimal regimens need to be identified., Objectives: To determine the optimal antenatal treatment of fetomaternal alloimmune thrombocytopenia to prevent fetal and neonatal haemorrhage and death., Search Strategy: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (28 February 2011) and bibliographies of relevant publications and review articles., Selection Criteria: Randomised controlled studies comparing any intervention with no treatment, or comparing any two interventions., Data Collection and Analysis: Two review authors independently assessed eligibility, trial quality and extracted data., Main Results: We included four trials involving 206 people. One trial involving 39 people compared a corticosteroid (prednisone) versus IVIG alone. In this trial, where analysable data were available, there was no statistically significant differences between the treatment arms for predefined outcomes. Three trials involving 167 people compared IVIG plus a corticosteroid (prednisone in two trials and dexamethasone in one trial) versus IVIG alone. In these trials there was no statistically significant difference in the findings between the treatment arms for predefined outcomes (intracranial haemorrhage; platelet count at birth and preterm birth). Lack of complete data sets and important differences in interventions precluded the pooling of data from these trials., Authors' Conclusions: The optimal management of fetomaternal alloimmune thrombocytopenia remains unclear. Lack of complete data sets for two trials and differences in interventions precluded the pooling of data from these trials which may have enabled a more developed analysis of the trial findings. Further trials would be required to determine optimal treatment (the specific medication and its dose and schedule). Such studies should include long-term follow up of all children and mothers.

Fetal/neonatal alloimmune thrombocytopenia is the most common cause of severe thrombocytopenia in the fetus and in an otherwise healthy newborn. To counter the consequences of severe fetal thrombocytopenia, antenatal therapies have been implemented. Predictive parameters for fetal severe thrombocytopenia are important for the development of noninvasive strategy and tailored intervention. We report here data concerning 239 pregnancies in 75 HPA-1bb women. Analysis of the index cases (diagnosis of fetal/neonatal alloimmune thrombocytopenia) did not show any significant correlation between the severity of the disease and the maternal genetic background (ABO blood group and HLA-DRB3 allele). Subsequent pregnancies were managed, and therapy effectiveness was evaluated. The highest mean newborn platelet count was observed for a combination of intravenous immunoglobulin and steroids (135 × 10⁹/L; 54 newborns) compared with intravenous immunoglobulin alone (89 × 10⁹/L; 27 newborns). The maternal anti-HPA-1a antibody concentration measured before any treatment and before 28 weeks of gestation was predictive of the fetal status. The weighted areas under curves of the maternal alloantibody concentrations were predictive of therapy response. To conclude, this large retrospective survey gives new insights on maternal predictive parameters for fetal status and therapy effectiveness allowing noninvasive strategies.

Neonatal alloimmune thrombocytopenia (NAIT) is the most common cause of severe thrombocytopenia in an otherwise healthy newborn. The most serious complication is intracranial hemorrhage, which can occur either in the fetus or the newborn. Despite the known serious sequelae, both antenatal management and neonatal treatment modalities are plagued by the lack of gold standard evidence to appropriately direct therapy. Maternal, risk-based therapeutic approaches range from invasive protocols to relatively benign noninvasive strategies to avoid serious procedural complications. Intravenous immunoglobulin (IVIG) with or without steroids and fetal blood sampling constitute the mainstay of antenatal management. Neonatal interventions principally focus on the use of antigen-negative compatible or random donor platelets and IVIG. While awaiting the results of controlled trials, each institution must develop a standardized, collaborative, multidisciplinary approach to the screening, diagnostic evaluation, and management of unexpected and anticipated NAIT based on experience, product availability, and emerging scientific data., (© Thieme Medical Publishers.)

In April 2010, a working group sponsored by the National Heart, Lung, and Blood Institute was assembled to identify research strategies to improve our understanding of alloimmunization caused by the transfusion of allogeneic blood components and to evaluate potential approaches to both reduce its occurrence and manage its effects. Significant sequelae of alloimmunization were discussed and identified, including difficulties in maintaining chronic transfusion of red blood cells and platelets, hemolytic disease of the newborn, neonatal alloimmune thrombocytopenia, and rejection of transplanted cells and tissues. The discussions resulted in a consensus that identified key areas of future research and developmental areas, including genetic and epigenetic recipient factors that regulate alloimmunization, biochemical specifics of transfused products that affect alloimmunization, and novel technologies for high-throughput genotyping to facilitate extensive and efficient antigen matching between donor and recipient. Additional areas of importance included analysis of unappreciated medical sequelae of alloimmunization, such as cellular immunity and its effect upon transplant and autoimmunity. In addition, support for research infrastructure was discussed, with an emphasis on encouraging collaboration and synergy of animal models biology and human clinical research. Finally, training future investigators was identified as an area of importance. In aggregate, this communication provides a synopsis of the opinions of the working group on the above issues and presents both a list of suggested priorities and the rationale for the topics of focus. The areas of research identified in this report represent potential fertile ground for the medical advancement of preventing and managing alloimmunization in its different forms and mitigating the clinical problems it presents to multiple patient populations., (© 2011 American Association of Blood Banks.)

Antibodies against human platelet antigens (HPAs) play important roles in thrombocytopenia. In Japan, HPA-4b antibody is frequently responsible for HPA-related neonatal alloimmune thrombocytopenia. A highly sensitive assay using platelets has been developed for the detection of antibodies against HPAs. However, it is difficult to obtain the platelets expressing specific HPAs required for the assay. Therefore, an alternative method not requiring platelets would be helpful to detect antibodies against HPAs. Glycoprotein IIIa (GPIIIa) cDNA encoding HPA-4b was individually co-transduced with that of wild-type GPIIb in K562 cells, which is a non-adherent cell line, using a retroviral vector. The expression of transgene products in cultured cells were observed for over 6 months. Next, to evaluating the sensitivity and specificity of this cell line panel, we performed monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay with a serum previously identified by another method. All HPA-4b antibodies in serum samples were positive, and all serum samples, including normal serum and serum containing HLA antibodies were negative. No difference was observed in the specificity and sensitivity between our method and conventional MAIPA using platelets. The present results indicate that this established cell line panel permits highly sensitive detection of specific antibodies against HPA-4b.

Human platelet antibodies are often implicated in conditions such as neonatal alloimmune thrombocytopenia (NAIT), idiopathic thrombocytopenic purpura (ITP) and platelet refractoriness; however, the frequency of such alloantibodies has not been reported in Nigeria and West Africa. A cross section of apparently healthy adult female staff at a tertiary health facility in the Niger Delta, Nigeria, was screened for alloantibodies to human platelet antigens (HPA) using the GTI PakPlus qualitative solid-phase enzyme-linked immunosorbent assay (ELISA) method. Among the 100 women screened, no anti-glycoprotein IIb/IIIa (anti-HPA-Ia,-3a and -4a) antibodies were detected; however, prevalence of anti-glycoprotein Ia/IIa (anti-HPA-5b) was 30% and pf anti-glycoprotein Ia/IIa (anti-HPA-5a) was 18%. Parity had a significant influence on the development to HPA antibodies (Fisher's Exact test: 11.683, P < 0.05; 13.577, P < 0.01). Platelet count did not have an influence on the development of antibodies (P > 0.05). Clearly, there is need to initiate platelet serology in this setting and also a need to educate women about the risk associated with frequent pregnancies. Furthermore, caution should be exercised when recruiting parous women as blood donors

The prevalence of antibodies to human platelet antigens (HPA) and human leukocyte antigens (HLA) class 1 antigens among Nigerian pregnant women has not been reported in our country. This study was therefore aimed at screening the obstetric population for evidence of alloimmunization due to human platelet and HLA class 1 antigens. One hundred and forty four (144) pregnant women attending the obstetric clinic of Military Hospital, Port Harcourt, participated in the study. Their sera were tested for antibodies to HPA and HLA class 1 antigens using GTI PakPlus solid phase ELISA Kit. The total prevalence rate of antibody production was 60.5% (87 out of 144). Among the positive samples, 60 had platelet glycoprotein specific antibodies (41.7%) and 27 had HLA class 1 antibodies (18.8%). In 39.6% of the pregnant women, both platelet specific antibodies and HLA class 1 antibodies appeared. The prevalence of platelet specific glycoprotein antibodies were obtained as follows: GP 11b/111a 12 (8.3%), GP 1a/11a 35 (20.8%), GP Ib/IX 18 (12.5%) and GP IV 9 (6.3%). The prevalence of each platelet antibody subgroup was obtained as follows: anti-HPA-1a,-3a,-4a (4.2%), anti-HPA-1b,-3b,-4a (4.2%), anti-HPA-30 5a and anti-GP Ib/IX (12.5% each), anti-HPA-5b (8.3%) and anti-GP IV (6.3%). A high prevalence rate of human platelet arid cytotoxic antibodies has been observed in our obstetric population. There is need to establish platelet serology laboratory for the proper antenatal and postnatal management of pregnant mothers in this region.

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.

Background: Antibodies to platelet (PLT) glycoprotein (GP) IV (CD36) have been implicated in rare cases of PLT refractoriness, particularly in non-Caucasians. We report two cases of PLT transfusion refractoriness linked to anti-CD36., Study Design and Methods: A 5-year-old female of Lebanese descent and a 70-year-old male of Chinese descent both failed to respond to HLA-matched PLT transfusions during acute myelogenous leukemia induction therapy. Antibody screening was performed using a PLT antibody solid-phase kit (PAKPLUS, GTI Diagnostics), followed by the monoclonal antibody-specific immobilization of PLT antigen (MAIPA) test and, for the second case, the modified antigen capture enzyme-linked immunosorbent assay (MACE)., Results: Both patients demonstrated antibody to GP IV (CD36) on the PAKPLUS assay. On MAIPA testing, both phenotyped as CD36 negative. Anti-CD36 was demonstrated by MAIPA in the first case. In the second case, antibodies were not detected by MAIPA and variably detectable by MACE, depending on the mouse monoclonal antibody (MoAb) used. Because no Canadian CD36-negative donors were available, antigen-negative plateletpheresis units from the BloodCenter of Wisconsin were successfully transfused., Conclusion: Two cases of clinically significant CD36 antibodies are reported. Investigation of one case was complicated by steric inhibition of binding in the MAIPA and MACE assays with certain MoAbs. The cases demonstrate the importance of maintaining an ethnically diverse pool of rare donors and the value of international cooperation in the management of these patients., (© 2010 American Association of Blood Banks.)

Background: For HLA-alloimmunized patients, platelet (PLT) concentrations are provided either at matched HLA-A and HLA-B loci or by serologic cross-reactivity groups (CREG) matching strategy. However, this method has some limitations., Study Design and Methods: In this study, the epitope-based matching (EBM) method was evaluated for selecting proper HLA-typed PLTs for patients with PLT transfusion refractoriness. Bead-based single-antigen HLA antibody detection method and HLAMatchmaker software were used to define the epitopes recognized by HLA-specific antibodies and to select compatible PLTs for nine patients with alloimmunized refractoriness. Corrected count increments (CCIs) were prospectively determined to compare successful transfusion rates among different matching methods in 142 PLT transfusions. In addition, HLA antibodies were serially detected to see whether any emerging antibodies appeared after receiving the EBM-matched PLTs., Results: The transfusion success rates evaluated with 1-hour CCIs for perfect matching or lacking any mismatching at HLA-A and -B locus (A/BU)-matched, CREG-matched, and EBM-matched PLTs were 85.2, 63.2, and 83.7%, respectively. Compared to CREG-matched PLTs, EBM-matched PLTs showed better transfusion results (p = 0.035). In the follow-up study (7 months; range, 3-13 months), no emerging HLA-specific antibodies were detected after receiving EBM-matched PLTs., Conclusions: EBM performed on the basis of bead-based single-antigen HLA antibody detection coupled with the HLAMatchmaker program is recommended in choosing proper PLTs for refractory patients when A/BU-matched PLTs were not available., (© 2010 American Association of Blood Banks.)

Introduction: Maternal-fetal alloimmune thrombocytopenia complicates about 0.1% of all pregnancies and is associated with major fetal and neonatal morbidity and mortality, especially spontaneous central nervous system bleeding leading to death and neurological handicaps. Successful prevention and treatment depend on the identification of at-risk possible carriers of anti-platelet antibodies., Case Report: We report a case of a mother with a previous child that developed neonatal hemorrhage; HPA-5b anti-platelet antibodies were detected post-natally. During the next pregnancy, fetal genotyping confirmed the presence of HPA-5b antigen; she was treated with weekly intravenous human immunoglobulin and oral prednisone. Pregnancy evolved without remarkable features and a full-term baby was delivered, with normal platelet counts., Conclusion: Fetal alloimmune thrombocytopenia is a potentially lethal condition, but early detection and prevention lead to successful outcome in most cases.

A 56 year-old, multiparous woman suffering from a myeloproliferative syndrome, who had received multiple red blood cell and platelet transfusions, was the recipient of an allograft of peripheral blood stem cells derived from her HLA-A, B, DR, DQ and DP and ABO identical sister, following myeloablative conditioning. The persistence of severe, isolated thrombopenia resistant to platelet transfusions led to the discovery of anti-HLA class I allo-immunisation. As HLA compatible platelet transfusions did not result in satisfactory platelet increments, we then discovered the simultaneous presence of anti-HPA-1a allo-immunisation. Genotyping of the HPA-1 systems of the patient (HPA-1B/B) and her sister (HPA-1A/B) enabled us to elucidate the mechanism underlying the persistent thrombopenia and the inefficacy of transfusion. In fact, only transfusion of HPA-1B/B platelets (HLA compatible or incompatible) proved to be efficacious. To reduce the level of anti-HPA-1a antibodies, we performed plasmapheresis sessions and used an anti-CD20 monoclonal antibody. It was only on achieving total haematopoietic chimerism, through rapid interruption of the immunosuppression, that we obtained spontaneous normalisation of the platelet count. The present case emphasises the necessity, before undertaking any allograft of haematopoietic stem cells - even if the latter come from a strictly HLA identical member of the family - of performing a search for eventual anti-HPA allo-immunisation., (Copyright © 2010 Elsevier Masson SAS. All rights reserved.)

Introduction: In a screening setting, maternal anti-HPA 1a antibody level has been found to be a good prognostic tool to identify newborns at risk for severe NAIT., Aim: Identify the optimal MAIPA protocol for quantitation of anti-HPA 1a antibodies., Materials and Methods: Plasma were analysed for anti-HPA 1a antibodies using different monoclonal antibodies, lyophilized or fresh platelets and MAIPA protocols., Results: The anti-HPA 1a antibody level varied significantly when different monoclonal antibodies were used. However, there was a strong correlation between maternal anti-HPA 1a antibody level and platelet count in the newborn. The sensitivity of the assay depended on the adopted MAIPA protocol., Conclusion: Consistent tests results are of importance for the clinical impact of the test., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Uncertainty regarding the pathophysiology of fetal and neonatal alloimmune thrombocytopenia (FNAIT) has hampered the decision regarding how to identify, follow-up and treat the women and children with this potentially serious condition. Since knowledge of the condition is derived mainly from retrospective studies, understanding of the natural history of this condition remains incomplete. General screening programs for FNAIT have still not been introduced, mainly because of a lack of reliable risk factors and effective treatment. Now, several prospective screening studies involving up to 100,000 pregnant women have been published and the results have changed the understanding of the pathophysiology of FNAIT and, thereby, the approach toward diagnostics, prevention and treatment in a more appropriate way.

Objective: To evaluate the clinical significance of MAIPA test in diagnosis of idiopathic thrombocytopenic purpura (ITP) and in the differential diagnosis of antoimmune thrombocytopenias from nonimmune thrombocytopenias., Methods: A total of 321 thrombocytopenic patients (118 males, 203 females) from 14 centers were studied. A modified monoclonal antibody immobilization of platelet antigen (MAIPA) method was used to detect the platelet glycoprotein-specific autoantibodies (anti-GP IIb/IIIa, anti-GPIb/IX) to double-blindly evaluate its sensitivity and specificity for the diagnosis of ITP and to investigate the impact of the antibodies on platelet count., Results: The results showed that for the diagnosis of ITP, anti-GPIIb/IIIa, anti-GPIb/IX and both of them had the sensitivity of 39.75%, 32.64% and 55.23%; the specificity of 97.56%, 93.94% and 92.68%; the positive predictive value of 97.94%, 93.98% and 95.65%; the negative predictive value of 35.71%, 32.35% and 41.53%; and the total efficiency of 54.51%, 48.29% and 64.80%, respectively. The positivity of the autoantibodies in immune thrombocytopenias was incredibly higher than that in nonimmune thrombocytopenias. The platelet counts in the immune thrombocytopenias with autoantibody positivities were significantly lower than those without the autoantibodies. The platelet counts were negatively correlated with the concentration of the autoantibodies. The levels of anti-GPIIb/IIIa or anti-GPIb/IX or both of them dropped or disappeared in patients being responsive to steroid therapy., Conclusion: MAIPA assay is proved to be of great value for the diagnosis of ITP and for differential diagnosis of immune thrombocytopenias from nonimmune thrombocytopenias.

Objective: To investigate the correlation between the platelet GP specific antibodies/HLA antibodies and platelet transfusion refractoriness (PTR)., Methods: Sixty-five patients with PTR were selected in this study and were genotyped for HLA-A and HLA-B as well as HPA systems by standard PCR-SSP assays. The platelet GP specific antibodies and HLA antibodies in serum and platelet elution were tested with a solid phase ELISA., Results: The HLA-A/B antigens and the frequencies of HPA-1, 2, 4, 5, 6, 9, 15 antigens in PTR patients had no difference from those in healthy donors. The freguencies of HPA-3a and 3b were 0.65 and 0.35, respectively. There was statistical difference between the 65 PTR patients and the healthy donors in HPA-3 freguencies (P < 0.05). Twenty-four patients (36.9 %) only expressed HLA antibodies, and 14 (21.5%) expressed HLA and platelet GP specific antibodies. The highest expression of anti-HLA-A/B specific antibodies was -A*9(46.2 %)/-B*40(33.6%), respectively. In serum, GPIIb/IIIa was expressed (26.2%), followed by GPIa/IIa (21.5 %). In platelet elution, GPIIb/IIIa was expressed of 41.5% and GPIb/IX 41.5%. Pedigree study was carried out for 2 patients. The results showed that the platelet GP specific antibody/HLA antibody developed in PTR patients was highly related to the mismatch with the platelet antigen/HLA antigen in their parents., Conclusion: The expressions of the HLA and platelet GP specific antibodies are the most important reason in PTR, it's meaningful to explore the correlation between PTR and HLA and HLA-A/B antigen in guiding platelet transfusion.

This study was purposed to determine the mode and size of human platelet antigens (HPA) typed platelet apheresis donor bank. The published data of HPA distribution collected from Chinese Han population of 16 provinces were analyzed. The combined data were tested with the Hardy-Weinberg equilibrium. The results showed that the bb homozygote was not detected in HPA-1, -4, -6, -10, and b gene was not found in HPA-7-9, 11-14, -16. There were 648 combined HPA 1-16 genotypes in Chinese Han population, and the cumulative frequency of 42 combinations higher than 0.001 were 0.9763. The highest frequency (0.2012) in combination was HPA-(7-8-9-11-12-13-14-16) aa - (1-4-5-6-10) aa-2aa-3ab-15ab. The probability of HPA dual antigen mismatch in HPA-15, -3 and -2 was higher than the 0.1, and the probability in the HPA-1, -5, and -6 was between 0.01 - 0.1. The probability of full-match in HPA1-16 antigens was 0.3195 in Chinese Han population after the random blood transfusion. According to the curve drawn by donor number (N) versus frequency (F), the regression equation LogN = -0.4394 x Ln (F) +0.4324 was derived at P = 95%. If the derived frequency (product of HPA frequency and ABO frequency) is 0.005, then the N should be 576.07 at least in Chinese Han population. It is concluded that the mode of regional, multi-center database of HPA-typed platelet apheresis donor bank may be acceptable in Chinese Han population, and the suitable number of HPA-typed platelet donor in one bank may be 600. Therefore, the bank can be used to treat the platelet transfusion refractoriness (PTR) caused by HPA-15, 3 and 2 mismatch mainly, and can be expanded effectively in similar genetic background to deal with the low-frequency HPA antigens mismatch. The number of HPA-typed platelet apheresis donor influences not only on the frequency of HPA, but also on the frequency of ABO group.

Objective: We sought to prevent intracranial hemorrhage (ICH) through antenatal management of alloimmune thrombocytopenia., Study Design: A total of 33 women (37 pregnancies) with alloimmune thrombocytopenia and ICH in a previous child were stratified according to the timing of the previous child's ICH: extremely high risk (HR) (n = 8) had ICH <28 weeks, very HR (n = 17) between 28-36 weeks, and HR (n = 12) in the perinatal period. Treatment was initiated at 12 weeks with intravenous immunoglobulin 1 or 2 g/kg/wk, and if the fetal platelet count by cordocentesis was <30,000/mL despite treatment, prednisone and/or more intravenous immunoglobulin were added., Results: Five of 37 fetuses suffered ICHs. Two ICHs had platelet counts >100,000/mL, and 1 was grade I. The other 2 ICHs were unequivocal treatment failures; both were grade III-IV and resulted in fetal demise., Conclusion: These findings demonstrate the success of stratified treatment in these HR patients, which tailored interventions according to the timing of the sibling's ICH., (Copyright (c) 2010 Mosby, Inc. All rights reserved.)