Genotyping for Human Platelet Alloantigen Polymorphisms: Applications in the Diagnosis of Alloimmune Platelet Disorders

Abstract

Molecular typing for platelet allelic polymorphisms was first made possible by discovery of the HPA-1a/1b single nucleotide polymorphism in 1989. Since then, six other biallelic human platelet antigen (HPA) systems have been determined and can be typed using genomic DNA. The introduction of polymerase chain reaction enabled development of several different assays including polymerase chain reaction-sequence-specific primer, melting curve analysis by LightCycler, and 5'-nuclease assays. More recently, multiplex polymerase chain reaction has allowed for the development of high-throughput assays for genotyping large numbers of patients and blood donors for not only platelet gene polymorphisms but also for those of other blood cell genes. Platelet genotyping is a valuable tool in confirming platelet antigen specificities of alloantibodies detected in patient sera to complement the clinical history in the diagnosis of alloimmune platelet disorders such as fetal and neonatal alloimmune thrombocytopenia (FNAIT), posttransfusion purpura, and multiplatelet transfusion refractoriness. In addition, it has made possible prenatal platelet typing of the fetus in suspected cases of FNAIT and large-scale blood donor typing for provision of antigen-negative platelets to transfuse highly alloimmunized patients. Platelet genotyping may also someday prove important as an aid in determining the relative risk of patients for various thrombotic disorders.

Human Platelet Antigen Alleles in 998 Taiwanese Blood Donors Determined by Sequence-Specific Primer Polymerase Chain Reaction

“…HPA alloimmunization is responsible for clinically relevant immune-mediated platelet disorders including fetal/neonatal alloimmune thrombocytopenia (FNAIT), posttransfusion purpura (PTP), and platelet transfusion refractoriness (PTR) [2–4]. HPA genotyping in different populations is of importance for predicting the risk of HPA alloimmunization in different ethnic groups [5]. This is essential, as a complement to clinical history, for FNAIT diagnosis and possible future prevention [6–8] and for provision of HPA-matched blood components for patients with PTR [4, 9].…”

New low‐frequency platelet glycoprotein polymorphisms associated with neonatal alloimmune thrombocytopenia

“…Automated sequence analysis was performed in both directions as described 18 . Genotyping of 100 normal donor DNA samples for the Sta and Kno mutations was performed using a Multicode‐PLx assay 30 . Fluorescence of PCR products was measured in a multiarray high‐throughput bead analyzer (Bioplex 200, Bio‐Rad, Hercules, CA).…”

Clinical Applications of Platelet Antibody and Antigen Testing

“…Multiple methods have been developed for HPA genotyping, and readers are encouraged to examine several detailed reviews on the subject. 22,29,30 Determining a patient's platelet genotype is helpful in confirming the HPA specificity of antibodies detected in the serum. For instance, if a patient has serum antibodies with apparent specificity for HPA-5a, then the patient would be expected to be homozygous for the HPA-5b allele and have the genotype HPA-5b/5b.…”