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Alpha-Globin Gene Deletion or Duplication

Test code(s) 16124X, 16125X (NY)

Question 1. My patient has abnormal RBC indices and HPLC results but has 4 intact alpha-globin genes. What can I do next?

  • Consider eliminating iron deficiency anemia as a possibility.
  • In the absence of iron deficiency, there may be other genetic causes for abnormal RBC indices and HPLC results. Point mutations in the alpha 1 and alpha 2 genes may be present. Alpha-Globin Gene Sequencing (test code 16116X [16117X for NY]) can detect point mutations in these genes. Please call 866-GENE-INFO to discuss the case, the patient’s indices, and additional testing options.

Question 2. My patient has 5 alpha-globin gene copies (an alpha globin triplication). What is the next step for family planning?

Both parents must be carriers of a thalassemia mutation for a pregnancy to be at risk. For example, if one parent carries an alpha-globin triplication (5 alpha gene copies) and the other parent carries a beta zero mutation, the fetus could be at risk for beta-thalassemia intermedia. The partner should be screened to determine his/her hemoglobinopathy carrier status (Hemoglobinopathy Evaluation, test code 35489X). Molecular genetic testing may also be appropriate for the partner. Please call 866-GENE-INFO to discuss the case with a genetic counselor.

Question 3. My patient's result indicates the deletion of 2 alpha-globin genes but doesn't identify the name of the mutation or differentiate between cis (both gene deletions in one chromosome) and trans (one gene deletion in each chromosome). What can I do?

For family planning purposes, it is important to determine which gene deletions are present and to distinguish whether the deletions are in cis or in trans. The Alpha-Globin Common Mutation Analysis test (test code 11175 [11174 for NY]) can detect the seven most common deletions and identify whether the deletions are in cis or in trans. This will help assess whether a fetus could be at risk for alpha-thalassemia major or hemoglobin H disease, if the partner is also an alpha-thalassemia carrier.

This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.

Document: FAQS.29 Revision: 1