Definition

The human platelet antigen system HPA-1 is based on a Leu33Pro polymorphism in platelet glycoprotein IIIa, encoded by the ITGB3 gene (17q21.32); a mismatch between the HPA-1a and HPA-1b alleles between mother and fetus can lead to antibody development and cause fetal and neonatal alloimmune thrombocytopenia (FNAIT). The risk of alloimmunization is markedly increased with the presence of HLA-DRB30101 and HLA-DQB10201.

Gene/region examined

HPA1 - a/b

Method

Sequence analysis

Accepted sample types

EDTA blood, AF, CVS

Inheritance

Inherited, a surface antigen polymorphism with codominant inheritance (not a disease, but it carries a risk of immunohematologic incompatibility).

Related Tests

Inheritance Patterns

Describes how a genetic condition is passed on within a family. There are five main patterns

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Carrier (Heterozygous / Homozygous)

Why it matters: In autosomal recessive inheritance, when each parent is a carrier (while both appear healthy), the chance of their child being born with the disease is 25% in each

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VUS (Variant of Uncertain Significance)

This is the situation where the test has detected a change in the DNA, but the role of this change in the development of disease is unconfirmed.

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How to Read a Genetic Test Result (Positive / Negative / VUS)

A genetic test result falls into three main categories

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Types of Genetic Tests

A genetic test is a type of medical test that detects changes in genes, chromosomes or proteins. Today there are more than 77,000 genetic tests available.

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