Human platelet-specific antigens frequencies in the Argentinean population

Fetal and neonatal alloimmune thrombocytopenia: a late or missed diagnosis disease in fetal and perinatal health-care settings

Introduction: Even though Fetal and Neonatal Alloimmune Thrombocytopenia (FNAIT) has been recognized as the main cause of primary hemorrhagic morbidity and mortality in fetuses and newborns, screening programs to detect pregnancies at risk have not yet been implemented in any country. Moreover, in spite of increased concerns about maternal, fetal and neonatal health care in general, this potentially lethal disease is still underdiagnosed. The aim of this report is to highlight the importance of considering FNAIT in fetal and perinatal health-care settings and show the usefulness of molecular tools in early diagnosis of this clinical entity.Methods: DNA was extracted from whole blood from parents and newborns; genotyping was performed by in house PCR using sequence-specific primers for typing Human Platelet Antigens (HPA)-1 to -6, -9, and -15, and with commercial HPA-TYPE (BAG HealthCare, Lich, Germany). Anti-HPA antibodies in the maternal serum were detected by the Monoclonal Antibody Solid Phase Platelet antibody Test (MASPAT). Chloroquine-treated platelets were used for the discrimination of platelet-specific antibodies from anti-HLA antibodies.Results: Patients 1 and 2 had severe thrombocytopenia due to incompatibility in HPA-1 and HPA-15, respectively. The third case was a thrombocytopenic neonate with severe bleeding complications other than ICH and in whom differential diagnosis between FNAIT and Von Willebrand congenital disease was necessary; incompatibility in HPA-15 was also demonstrated. Case 4 represents a missed diagnostic opportunity.Conclusion: This is the first report of FNAIT cases confirmed by molecular evidence and anti-HPA antibodies detection in Argentina. This report reinforces the relevance of early diagnosis of this clinical entity. Since the delay in FNAIT diagnosis could lead to severe consequences in the fetus and neonates, strategies to approach maternal, fetal, and perinatal health, as well as prevention policies aimed to reduce fetal and neonatal morbidity and mortality should focus on implementing programs to identify high-risk pregnancies and thus reduce thrombocytopenia-related complications in fetuses and newborns.

High-Throughput Screening of Blood Donors for Twelve Human Platelet Antigen Systems Using Next-Generation Sequencing Reveals Detection of Rare Polymorphisms and Two Novel Protein-Changing Variants

Background

Exposure to non-matching human platelet alloantigens (HPA) may result in alloimmunization. Antibodies to HPA can be responsible for post-transfusion purpura, refractoriness to donor platelets, and fetal and neonatal alloimmune thrombocytopenia. For the supply of compatible apheresis platelet concentrates, the HPA genotypes are determined in a routine manner.

Methods

Here, we describe a novel method for genotyping twelve different HPA systems simultaneously, including HPA-1 to HPA-5, HPA-9w, HPA-10w, HPA-16w, HPA-19w, HPA-27w, and the novel HPA-34w by means of amplicon-based next-generation sequencing (NGS). Blood donor samples of 757 individuals with a migration background and 547 of Western European ancestry were genotyped in a mass-screening setup. An in-house software was developed for fast and automatic analysis. TaqMan assay and Sanger sequencing results served for validation of the NGS workflow. Finally, blood donors were divided in several groups based on their country of origin and the allele frequencies were compared.

Results

For 1,299 of 1,304 samples (99.6%) NGS was successfully performed. The concordance with TaqMan assay and Sanger sequencing results was 99.8%. Allele-calling dropouts that were observed for two samples with the TaqMan assay caused by rare single nucleotide polymorphisms were resolved by NGS. Additionally, twenty rare and two novel variants in the coding regions of the genes ITGB3, GPB1A, ITGBA2, and CD109 were detected. The determined allele frequencies were similar to those published in the gnomAD database.

Conclusions

No significant differences were observed in the distribution of allele frequencies of HPA-1 through HPA-5 and HPA-15 throughout the analyzed groups except for a lower allele frequency for the HPA-1b allele in the group of donors with Southern Asian ancestry. In contrast, other nucleotide variants that have not yet been phenotypically characterized occurred three times more often in blood donors with a migration background. High-throughput amplicon-based NGS is a reliable method for screening HPA genotypes in a large sample cohort simultaneously. It is easily upgradeable for genotyping additional targets without changing the setup or the analysis pipeline. Mass-screening methods will help building up blood donor registries to provide matched blood products.

[Polymorphism of human platelet antigens in Tunisian population: Clinical and anthropological interests]

OBJECTIVES

Human Platelet Antigens (HPA) are of considerable interest in obstetric transfusion medicine and anthropological genetics. This study aims to provide clinicians with a detailed database of HPA antigenic variants, which allows them to estimate the probability of allo-immunisation of each antigen. In addition, it aims to make an interethnic comparison of the Tunisian population with other populations.

METHODS

The target population consists of 324 healthy and unrelated Tunisian blood donors recruited from the National Blood Transfusion Center in Tunis. DNA extraction was performed by the Salting Out method and molecular genotyping was performed by the PCR-SSP technique. The statistical analysis was performed using two approaches: manual calculation and computerized calculation. Phylogenetic trees were constructed through the use of Standard Genetic Distances that were calculated from allelic frequencies.

RESULTS

With the exception of the HPA-4 system, statistical analysis showed that all HPA systems are polymorphic especially the two systems HPA-3 and HPA-15. The inter-ethnic analysis showed that Tunisians are closer to North Africans and Caucasians than Sub-Saharan and Asian populations, which shows genetic mixing between Tunisians, Arabs, Europeans and Africans.

CONCLUSION

The results of this study could be exploited to prepare a ready-to-use genotyping plate dedicated to HPA antigens, with the aim of ensuring better management, especially for polytransfused patients.

Human Platelet Antigens in Brazilian Multiethnic Populations: Occurrence of Regional Variation and Frequency in a Large Urban Center (Belo Horizonte)

Background

The frequency of human platelet antigens (HPA) varies according to ethnicity, which causes differences in the morbidity of alloimmune and autoimmune thrombocytopenic disorders in different populations. Studies on HPA frequencies in Brazil have reported differences among Brazilian populations produced by the diverse degrees of admixture throughout the country.

Methods

In the present study, we investigated the variation of HPA distribution in Brazil, compared with worldwide populations, and describe the frequencies of HPA-1, -2, -3, -5, and -15 in a large urban center in Southern Brazil (Belo Horizonte) based on a sample of blood donors.

Results

The principal component analysis and the dendrogram based on genetic distance revealed a clear relationship between Brazilian populations and the groups formed by European and African populations. The coefficients of variation for HPA allele frequencies suggest that Brazilian populations presented variations for HPA alleles comparable with the populations from continental groups. In Belo Horizonte, the allele a frequencies for HPA-1, -2, -3, -5 and -15 were 0.8575, 0.8400, 0.6225, 0.8525 and 0.5825 respectively. The genotypes with higher frequencies were a/a (72-74%), except for HPA-3 and -15, whose heterozygous a/b genotypes were shown to be more prevalent (43.5 and 44.5%, respectively).

Conclusion

We confirmed the heterogeneity of HPA antigens in Brazilian populations, reinforcing the importance of HPA panels composed of regional blood donors, or a national panel that contemplates the specificities of the different regions of the country, in order to provide support in platelet transfusions and to minimize the risks associated with HPA alloimmunization. The evaluation of HPA data from Belo Horizonte represents the initial step toward the development of a genotyped platelet donor registry in order to treat HPA alloimmunized patients in this region.

A study of human neutrophil antigen genotype frequencies in Hong Kong

BACKGROUND

Alloantibodies against human neutrophil antigens (HNA) are associated with a variety of clinical conditions. Over the past decade, the allelic and genotypic frequencies of the five HNA systems have been evaluated. Although the HNA system is less polymorphic than human leukocyte antigens (HLA), significant differences in the genotypic and allele frequencies still exist in different populations, even those living in close proximity.

OBJECTIVES

To delineate HNA genotypic and allele frequencies to provide vital information on estimating the risk of HNA-associated diseases for our local population.

METHODS

Using a validated, in-house-developed assay, genotyping for HNA-1, HNA-3, HLA-4 and HNA-5 was performed on 300 samples from Chinese blood donors from Hong Kong. In addition, the frequency of the HNA-2 c.843A > T allele was also determined.

RESULTS

The allele frequencies of HNA-1a, -1b and -1c alleles were 67·8, 31·5 and 0%, respectively, whereas the frequencies of HNA-3a and HNA-3b were 71·0 and 29·0%, respectively. The frequencies of HNA-4a and -4b alleles were 99·5 and 0·5%, respectively, and for HNA-5a and -5b, alleles were 85·2 and 14·8%, respectively. Homozygotes for the HNA-2 c.843 TT variant were absent in our population, whereas only <4% of the population were c.843AT heterozygote carriers.

CONCLUSIONS

This is the first study to define HNA genotype and allele frequencies using a validated modified in-house PCR-SSP method in the Hong Kong Chinese blood donor population. Our approach provides a cost-effective assay for conducting routine HNA typing and facilitates the incorporation of these assays into routine clinical service. Our results are comparable with those reported in the Guangzhou Chinese population, but the allele frequencies in our Hong Kong Chinese population are significantly different from the reported European frequencies, confirming that a geographical difference exists for HNA allele frequencies.

Human platelet antigen 1, 2 and 5 gene polymorphisms in Egyptians and their potential association with susceptibility to immune thrombocytopenic purpura in Egyptian patients

OBJECTIVES

This study determined the incidence of HPA1, HPA2 and HPA5 polymorphisms in 120 Egyptian immune thrombocytopenic purpura (ITP) patients and 120 healthy Egyptian subjects.

METHODS

Human platelet antigen (HPA) genotyping was done using the polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The frequency of HPA1 allele a and b was 78.75 and 21.25% in controls, 80.8 and 19.2% in ITP, respectively. HPA2 allele a and b frequency was 86.25 and 13.75% in controls and of 74.6 and 25.4% in patients, respectively. HPA5 allele a and b frequency was 87.5 and 12.5% in controls, in patients it was 85 and 15%, respectively. With the exception of HPA2, no other significant difference was encountered in HPA allele frequency between controls and ITP patients.

DISCUSSION

Egyptian HPA profile is closely linked to Middle East and neighboring Arabs. The current study noted that in all the studied HPA systems 1, 2 and 5, the 'a' allele is more prevalent than the b allele; the most frequent genotype was the homozygous a/a genotype. HPA2b frequency, homo- and hetero-zygous HPA2b genotype frequencies were significantly higher in ITP patients compared to controls.

CONCLUSION

HPA 2b are 2.37 times more likely to develop ITP compared to those without this allele. The relatively high allele frequency of the HPA-1b in the Egyptian population suggests that this ethnic group has a higher risk of alloimmunization.

Genetic polymorphisms of human platelet antigens in Euro-African and Japanese descendants from Parana, Southern Brazil

The frequency distributions of HPA-1 to HPA-6 and HPA-15 were evaluated in two Brazilian populations from Parana: a mixed population of predominantly Caucasians and a population of Japanese descendants. Genotyping was performed by PCR-SSP in 364 unrelated individuals. Differences in the distribution of HPA highlight diversity in Brazilian miscegenation and the importance of formation of the HPA panel composed of regional blood donors.

Human platelet antigens in Burmese, Karen and north-eastern Thais

OBJECTIVES

A comparative study of allele frequencies at HPA-1 to -6 and HPA-15 in Burmese and Karen populations as well as at HPA-15 in north-eastern Thais (NET) is presented.

BACKGROUND

Human platelet antigens (HPAs) are clinically important in several immune platelet disorders, including foetal and neonatal alloimmune thrombocytopenia (FNAIT), post-transfusion purpura (PTP) and platelet transfusion refractoriness (PTR). The knowledge of antigen frequencies in a population is essential for the evaluation of patients suffering from immune-mediated platelet disorders.

METHODS

A total of 285 unrelated, healthy Burmese, 242 Karen and 300 NET were recruited to this study. Genotype and allele frequencies of HPA-1 to -6 and HPA-15 were defined using polymerase chain reaction sequence-specific primers (PCR-SSP) RESULTS: No individuals homozygous for HPA-1bb, -2bb, -4bb, -5bb and -6bb were detected. HPA-1a, -2a, -4a, -5a and -6a were present in all samples of Burmese and Karen origin. HPA-1b, -2b, -4b, -5b and -6b were rare in these populations. The frequencies of HPA-3a/-3b were 60·4/39·6% in Burmese and 55·8/44·2% in Karen, respectively. Frequencies of HPA-15a/-15b were 57·2/42·8% in Burmese, 52·5/47·5% in Karen and 49·8/50·2% in NET.

CONCLUSIONS

The frequencies of HPA genotypes in our study indicates that HPA-1a, -2a, -4a, -5a and -6a are unlikely involved in FNAIT, PTP and PTR in Burmese and Karen populations. However, HPA-1b, -2b, -3a, -3b, -4b, -5b, -6b, -15a and -15b may likely stimulate alloantibodies in these populations.

Gene frequency of human platelet alloantigens-1 to -6 and -15 in Saudi blood donors

BACKGROUND

Human platelet antigens (HPAs) are involved in the pathogenesis of several clinical conditions, such as platelet transfusion purpura (PTP), refractoriness to platelet transfusion and neonatal alloimmune thrombocytopenia (NAITP). Typing of HPA (1-6 and 15) has not been carried on the Saudi population. This is the first study of all the seven HPA systems on Arabs. The aim of this prospective study was to determine the frequency of HPA (1-6 and 15) in Saudis.

STUDY DESIGN AND METHODS

A total of 100 randomly selected Saudi blood donor samples were genotyped using the polymerase chain reaction with sequence-specific primers (PCR-SSP).

RESULTS

The most common HPA genotypes among Saudis were HPA-1 a + b- (75%), HPA-2 a + b- (62%), HPA-3 a + b- (51·5%), HPA-4 a + b- (99%), HPA-5 a + b- (76·5%), HPA-6 a + b- (100%) and HPA-15 a + b + (50%). The prevalent allele among the HPA systems was (a), except in the HPA-15 system where the (b) allele was found in 52% of the subjects. Comparisons with other ethnic populations uncovered marked differences in the distribution of HPA alleles.

CONCLUSION

Studying the prevalence of HPA antigens in Saudi population will help in the understanding of its role in platelet-related disorders. It will also enable the blood bank to establish an HPA-based donor registry that will be a valuable source of compatible platelet-therapeutic products to alloimmunised patients. This will also enhance the safety and efficacy of platelet transfusion. This data obtained will form an addition to the existing body of literature in transfusion research.

Triplets with neonatal alloimmune thrombocytopenia due to antibodies against human platelet antigen 1a

BACKGROUND

Neonatal alloimmune thrombocytopenia (NAIT) has been reported only rarely in twins and not at all, to our knowledge, in triplets.

CASE REPORT

Nonidentical triplets were born with severe thrombocytopenia. Nadir platelet (PLT) counts were 17 × 10⁹ , 12 × 10⁹ , and 10 × 10⁹ /L. NAIT was confirmed by an incompatibility for human PLT antigen (HPA)-1a and the presence of maternal anti-HPA-1a. The maternal genotype was HPA-1bb and the paternal genotype was HPA-1aa; thus, all children were affected.

RESULTS

PLT counts for each infant improved with the administration of random-donor PLT transfusions. All three infants also received intravenous immunoglobulin. None had major bleeding. A small isolated subependymal hemorrhage was found incidentally in one infant; this remained stable on repeat imaging.

CONCLUSIONS

This is the first report of triplets with NAIT. Anti-HPA-1a is sufficiently potent to affect three infants simultaneously. Random-donor PLTs were effective in improving PLT counts in all three infants.

Human neutrophil antigen profiles in Banjar, Bugis, Champa, Jawa and Kelantan Malays in Peninsular Malaysia

BACKGROUND

Human neutrophil antigens (HNA) are polymorphic and immunogenic proteins involved in the pathogenesis of neonatal alloimmune neutropenia, transfusion-related acute lung injury (TRALI) and transfusion-related alloimmune neutropenia. The characterisation of HNA at a population level is important for predicting the risk of alloimmunisation associated with blood transfusion and gestation and for anthropological studies.

MATERIALS AND METHODS

Blood samples from 192 healthy, unrelated Malays were collected and genotyped using polymerase chain reaction-sequence specific primers (HNA-1, -3, -4) and polymerase chain reaction-restriction fragment length polymorphisms (HNA-5). The group comprised 30 Banjar, 37 Bugis, 51 Champa, 39 Jawa and 35 Kelantan Malays.

RESULTS

The most common HNA alleles in the Malays studied were HNA-1a (0.641-0.765), -3a (0.676-0.867), -4a (0.943-1.000) and -5a (0.529-0.910). According to principal coordinate plots constructed using HNA allele frequencies, the Malay sub-ethnic groups are closely related and grouped together with other Asian populations. The risks of TRALI or neonatal neutropenia were not increased for subjects with HNA-1, -3 and -4 loci even for donor and recipient or pairs from different Malay sub-ethnic groups. Nonetheless, our estimates showed significantly higher risks of HNA alloimmunisation during pregnancy and transfusion between Malays and other genetically differentiated populations such as Africans and Europeans.

DISCUSSION

This study reports HNA allele and genotype frequencies for the five Malay sub-ethnic groups living in Peninsular Malaysia for the first time. These Malay sub-ethnic groups show closer genetic relationships with other Asian populations than with Europeans and Africans. The distributions of HNA alleles in other lineages of people living in Malaysia (e.g. Chinese, Indian and Orang Asli) would be an interesting subject for future study.

Human platelet antigens frequencies in Maori and Polynesian populations

BACKGROUND

Allele frequencies of human platelet antigens (HPA) reflect population history and possibility of platelet-specific alloimmunization. Here, we report on screening of variants at HPA loci for Polynesian and Maori subjects.

OBJECTIVES

Our aims are to evaluate new HPA genotyping methods, compile and analyse new HPA datasets for these subjects, use HPA data for tracing ancestry, migration patterns, genetic admixture and its potential influence on health.

MATERIALS AND METHODS

A total of 75 Maori and 25 Polynesian DNA samples were genotyped using commercial BAGene HPA-TYPE DNA-SSP kits, BLOODchip hybridization SNP assays and DNA sequence based typing.

RESULTS

Genotyping was successful and cross validation of PCR-SSP and BLOODchip gave 100% agreement. Among the HPA loci tested, only six are dimorphic (HPA-1 to -3, -5, -6 and -15) and all others are monomorphic. The Polynesians and Maori have the 'a' allele form as the most common for all loci except HPA-15.

CONCLUSIONS

The newly observed HPA data as well as principal coordinate analysis clearly indicate genetic contributions from both, Asia and Australasia in Maori and Polynesian populations together with recent admixture with Europeans. In addition, different prevalences of HPA alleles among Polynesian, Maori and European populations contribute towards different risk profiles for platelet-specific alloimmunization. This is the first report for these populations and our findings are of direct practical relevance for blood transfusion centres, the management of pregnancies, assessment of neonatal alloimmune thrombocytopenia and management of multi-transfused patients.

Human neutrophil alloantigen genotype frequencies among blood donors with Turkish and German descent

Antibodies against the human neutrophil antigens (HNA) are able to stimulate transfusion reactions, autoimmune and neonatal neutropenia. The aim of this study was to determine the HNA allele frequencies in the largest ethnic minority group in Germany in comparison with the German population for predicting the risk of alloimmunization and associated transfusion reactions, as well as the risk of developing neonatal neutropenia for the newborn of racial mixed couples. However, there exists no data about HNA genotype distribution in Turkish population. DNA was isolated from blood samples of 119 German and 118 Turkish blood donors and typed them for HNA-1, -3, -4, and -5 by using a commercial polymerase chain reaction kit with sequence-specific primers (SSP-PCR) and compared the HNA genotype distribution of both groups. In German blood donors, the gene frequencies for HNA-1a and HNA-1b were 0.391 and 0.601, for HNA-3a and -3b, 0.744 and 0.256, for HNA-4a and -4b, 0.908 and 0.092, and for HNA-5a and -5bw, 0.731 and 0.269. In Turkish blood donors, we observed 0.420/0.564, 0.737/0.263, 0.881/0.119, and 0.754/0.246 for HNA-1a/1b, -3a/3b, -4a/4b, and -5a/5bw. No statistic significant difference between genotypes in these populations was observed. This study is the first to report HNA gene frequencies in a Turkish population. It showed that there is no difference of HNA genotype in blood donors with Turkish descent in comparison with German blood donors. The alternating transfusion of blood and blood components is no increased risk for developing alloantibodies against HNA antigens. In pregnancy of mixed couples no special screening programs for HNA are necessary.

The allele frequencies of HPA 1-16 determined by PCR-SSP in Chinese Cantonese donors

BACKGROUND

Typing of human platelet antigens (HPA) has proven to be useful in some clinical situations related to platelet alloimmunization.

OBJECTIVE

The objective of this study was to investigate HPA 1-16 and to determine genotype and allele frequencies by polymerase chain reaction-sequence specific primer (PCR-SSP) in apheresis platelet donors in Guangzhou Blood Center.

METHODS

A total of 200 random samples from donors were involved in the study. Genotype and allele frequencies of HPA 1 to 16 were detected by PCR-SSP method.

RESULTS

The frequencies obtained from these donors were 99·50 and 0·50% for HPA-1a and -1b; 96·25 and 3·75% for HPA-2a and -2b; 54·25 and 45·75% for HPA-3a and -3b; 99·50 and 0·50% for HPA-4a and -4b; 99·00 and 1·00% for HPA-5a and -5b; 97·00 and 3·00% for HPA-6a and -6b and 42·25 and 57·75% for HPA-15a and -15b. There is only a/a homozygosis detected in HPA-7, -8, -9, -10, -11, -12, -13, -14 and -16. In this study, none of HPA-1b/ 1b, -2b/2b, -5b/5b homozygosis were detected which were found in other racial groups. One homozygosis of HPA-6b/6b in 200 individuals was detected which was not found in a study involving 1000 Chinese (Feng et al., 2006).

CONCLUSION

The HPA-3 and -15 appear to the highest priority and HPA-2, -6, -5 -1 and -4 to be the second priority in Chinese Cantonese when it comes to the diagnosis of neonatal alloimmune thrombocytopenia and to provide the HPA-matched platelet for patients with platelet transfusion refractoriness. The PCR-SSP method makes it possible to detect genotype of HPA-1 to -16 in less than 4 h and to establish a donor database for HPA genotype in a blood bank.

Platelet-specific alloantigens and antibodies in Tunisian women after three or more pregnancies

Pregnancy may allow alloimmunization against human platelet antigens (HPA), which can lead to neonatal alloimmune thrombocytopenia (NAIT). The specificities of alloantibodies are closely related to the distribution of the HPA systems. A total of 281 Tunisian multiparous women (mean number of pregnancies: 4.5) were phenotyped for the HPA-1, -3 and -5 systems, by monoclonal antibody immobilization of platelet antigens (MAIPA). We searched for antibodies against HPA-1a, HPA-3a, HPA-5b and HPA-5a in HPA-1b1b, HPA-3b3b, HPA-5a5a and HPA-5b5b individuals, respectively. The gene frequencies were: 0.83 for HPA-1a, 0.17 for HPA-1b, 0.78 for HPA-3a, 0.22 for HPA-3b, 0.82 for HPA-5a and 0.18 for HPA-5b. Anti-HPA-5b antibodies were present in eight sera and anti-HPA-3a antibodies were present in one serum. The anti-HPA-5b system is the most frequently involved in platelet alloimmunization in Tunisian multiparous women. However, prospective trials are required to confirm this result and to determine the exact frequencies and clinical relevance of platelet alloantibodies in pregnant Tunisian women.

Allele frequencies of the human platelet antigen-1 in the Egyptian population

Background

The human platelet alloantigen system HPA-1 in the Egyptian population was examined by polymerase chain reaction using sequence-specific primers (PCR-SSP). The objectives of this study were to evaluate the allele frequency of HPA-1a and -1b in healthy Egyptian individuals and compare these with the international literature. Human platelet antigen (HPA) systems are associated with alloimmunization and organ transplantation rejection as well as the development of cardiovascular disease. Of the various HPA systems, HPA-1 specifically has been considered to be the most important antigenic system implicated in the Caucasian population. No study has yet examined this system in the Egyptian populations, however. We therefore investigated the allele frequency of the HPA-1 system in the Egyptian population.

Findings

To determine the allele frequency of the HPA-1a and -1b, we tested genomic DNAs from 206 healthy, unrelated Egyptian individuals using PCR-SSP. Our results showed that the 1a/1a genotype was the most predominant (59.22%) followed by 1a/1b (34.95%) and 1b/1b (5.83%) with allele frequencies for 1a and 1b of 0.77 and 0.23, respectively, in the population.

Conclusion

As compared with other geographic groups, a relatively high allele frequency of the HPA-1b in the Egyptian population may indicate a higher risk of alloimmunization. This study is the first to investigate the allele frequency of the HPA-1 system in the Egyptian population and serves as an outline for future clinical research associated with platelet disorders in this group.