Definition

The HBA1 and HBA2 genes encode the alpha globin chains of hemoglobin; sequence analysis is used to detect point mutations that cannot be explained by large deletions and abnormal hemoglobin variants such as Hb Constant Spring. Depending on the number of genes affected, clinical severity ranges from silent carrier status to alpha thalassemia minor, Hemoglobin H disease and Hb Bart hydrops fetalis.

Gene/region analyzed

HBA - Exon 1, HBA - Exon 2, HBA - Exon 3

Method

Sequence analysis

Accepted sample types

EDTA blood, AF, CVS

Inheritance

Hereditary, autosomal recessive/codominant inheritance pattern (severity depends on gene dosage).

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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