Alpha-thalassemia X-Linked Intellectual Disability XLID : ATR-X Sequencing

Test Information

ATR-X sequencing is a molecular test used to identify variants in the gene associated with Alpha-thalassemia X-Linked Intellectual Disability (XLID).

Turnaround Time

6 weeks

CPT Code(s)





Clinical Information

Alpha-thalassemia X-linked Intellectual Disbility (ATR-X) is an XLID condition caused by mutations in the ATRX/XNP gene localized to Xq13. Males usually present with moderate intellectual disability and characteristic hypotonic facies, consisting of small head size, depressed nasal bridge, large open mouth, large prominent lips and an inverted upper lip. Carrier females exhibit no features, a result of highly skewed X-inactivation. Males can sometimes exhibit hemoglobin H inclusion bodies but this clinical test is unreliable for diagnosis purposes.


Molecular testing is useful to confirm the diagnosis and to identify the disease causing mutations within a family to allow for carrier testing and prenatal diagnosis.


Sanger Sequencing


Sequencing of ATR-X will detect a mutation in 95% of individuals with this disorder.

Specimen Requirements

5 to 7 ml of peripheral blood collected in an EDTA (lavender top) tube is the preferred specimen type. The minimal blood needed for reliable DNA isolation is 3 ml. Extracted DNA, dried blood spots, and saliva are also accepted for this test.

Transport Instructions

The specimen should be kept at room temperature and delivered via overnight shipping. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.

Prenatal Testing Information

Prenatal diagnosis is available if the familial mutations are known. Additional fees for cell culture and maternal cell contamination may apply. Maternal cell contamination studies are required for all prenatal molecular tests. Contact the laboratory prior to sending a prenatal specimen.

Have Questions Need Support?

Call our laboratory at 1-800-473-9411 or contact one of our Laboratory Genetic Counselors for assistance.
Robin Fletcher, MS, CGC
Kellie Walden, MS, CGC

Molecular Testing, Sanger Sequencing
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