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Test ID: XALDZ X-Linked Adrenoleukodystrophy, Full Gene Analysis, Varies

Reporting Name

X-ALD, Full Gene Analysis

Useful For

Confirming a diagnosis of X-linked adrenoleukodystrophy

 

Identifying a variant in the ABCD1 gene

Clinical Information

X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disease characterized by magnetic resonance imaging (MRI) findings in the white matter, adrenocortical insufficiency, and abnormal plasma concentrations of very long chain fatty acids. The phenotypic expression of X-ALD varies widely. The phenotypes can be subdivided into 3 main categories: childhood cerebral form, adrenomyeloneuropathy (AMN), and Addison disease only. The childhood cerebral form has onset of symptoms between ages 4 and 8, beginning with attention deficit hyperactivity disorder-like symptoms with progressive cognitive, behavior, vision, hearing, and motor deterioration. AMN usually presents in males in their late twenties as progressive paraparesis, sexual dysfunction, sphincter disturbances, and abnormalities in adrenocortical function. The Addison only phenotype typically presents by age 7.5 with adrenocortical insufficiency without significant neurological involvement. Most of these patients eventually develop AMN. Some female carriers may experience mild AMN symptoms with a later age of onset.

 

The phenotype cannot be predicted by very long chain fatty acids (VLCFA) plasma concentration or by the nature of the genetic variant. The same variant can be associated with each of the known phenotypes. Different phenotypes often occur within a family.

 

POX / Fatty Acid Profile, Peroxisomal (C22-C26), Serum testing is the preferred first-tier screening method for X-ALD. This is abnormal in 99% of affected males and 85% of carrier females. Sequencing of the ABCD1 gene is available to confirm the diagnosis of X-ALD, improve carrier detection, and assist with prenatal diagnosis.

Interpretation

All detected alterations are evaluated according to American College of Medical Genetics and Genomics recommendations.(1) Variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
CULFB Fibroblast Culture for Genetic Test Yes No

Testing Algorithm

For skin biopsy or cultured fibroblast specimens, fibroblast culture testing will be performed at an additional charge. If viable cells are not obtained, the client will be notified.

 

For more information see

-Newborn Screen Follow-up for X-Linked Adrenoleukodystrophy

-Newborn Screening Act Sheet X-linked Adrenoleukodystrophy: Increased Very Long Chain Fatty Acids

Report Available

14 to 20 days

Day(s) Performed

Varies

Clinical Reference

1. Richards S, Aziz N, Bale S, et al: Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med. 2015 May;17(5):405-424

2. Moser HW, Mahmood A, Raymond GV: X-linked adrenoleukodystrophy. Nat Clin Pract Neurol. 2007 Mar;3(3):140-151

3. Wang Y, Busin R, Reeves C, et al: X-linked adrenoleukodystrophy: ABCD1 de novo mutations and mosaicism. Mol Genet Metab. 2011 Sep-Oct;104(1-2):160-166

4. Kemp S, Berger J, Aubourg P: X-linked adrenoleukodystrophy: Clinical, metabolic, genetic and pathophysiological aspects. Biochim Biophys Acta. 2012 Sept;1822(9):1465-1474

Method Name

Polymerase Chain Reaction (PCR) followed by DNA Sequencing

Specimen Type

Varies


Ordering Guidance


The preferred first-tier screening test for X-linked adrenoleukodystrophy is POX / Fatty Acid Profile, Peroxisomal (C22-C26), Serum.



Shipping Instructions


Specimen preferred to arrive within 96 hours of collection.



Specimen Required


Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.

 

Submit only 1 of the following specimens:

 

Preferred:

Specimen Type: Whole blood

Container/Tube:

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send whole blood specimen in original tube. Do not aliquot.

Specimen Stability Information: Ambient (preferred)/Refrigerated

 

Specimen Type: Cultured fibroblasts

Container/Tube: T-75 or T-25 flask

Specimen Volume: 1 Full T-75 flask or 2 full T-25 flasks

Specimen Stability Information: Ambient (preferred)/Refrigerated <24 hours

Additional Information: A separate culture charge will be assessed under CULFB / Fibroblast Culture for Biochemical or Molecular Testing. An additional 3 to 4 weeks is required to culture fibroblasts before genetic testing can occur.

 

Supplies: Fibroblast Biopsy Transport Media (T115)

Specimen Type: Skin biopsy

Container/Tube: Sterile container with any standard cell culture media (eg, minimal essential media, RPMI 1640). The solution should be supplemented with 1% penicillin and streptomycin.).

Specimen Volume: 4-mm punch

Specimen Stability Information: Refrigerated (preferred)/Ambient

Additional Information: A separate culture charge will be assessed under CULFB / Fibroblast Culture for Biochemical or Molecular Testing. An additional 3 to 4 weeks is required to culture fibroblasts before genetic testing can occur.

 

Specimen Type: Blood spot

Supplies: Card - Blood Spot Collection (Filter Paper) (T493)

Container/Tube:

Preferred: Collection card (Whatman Protein Saver 903 Paper)

Acceptable: PerkinElmer 226 (formerly Ahlstrom 226) filter paper, or blood spot collection card

Specimen Volume: 2 to 5 Blood spots

Collection Instructions:

1. An alternative blood collection option for a patient older than 1 year is a fingerstick. For detailed instructions, see How to Collect Dried Blood Spot Samples.

2. Let blood dry on the filter paper at ambient temperature in a horizontal position for a minimum of 3 hours.

3. Do not expose specimen to heat or direct sunlight.

4. Do not stack wet specimens.

5. Keep specimen dry.

Specimen Stability Information: Ambient (preferred)/Refrigerated

Additional Information:

1. Due to lower concentration of DNA yielded from blood spot, it is possible that additional specimen may be required to complete testing.

2. For collection instructions, see Blood Spot Collection Instructions.

3. For collection instructions in Spanish, see Blood Spot Collection Card-Spanish Instructions (T777).

4. For collection instructions in Chinese, see Blood Spot Collection Card-Chinese Instructions (T800).


Specimen Minimum Volume

Blood: 1 mL
Blood Spots: 5 punches-3 mm diameter

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Varies

Reference Values

An interpretive report will be provided.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

81405-ABCD1 (ATP-binding cassette, sub-family D [ALD] member 1) (eg, adrenoleukodystrophy) full gene sequence

88233-Tissue culture, skin or solid tissue biopsy (if appropriate)

88240-Cryopreservation (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
XALDZ X-ALD, Full Gene Analysis 95782-9

 

Result ID Test Result Name Result LOINC Value
53561 Result Summary 50397-9
53562 Result 82939-0
53563 Interpretation 69047-9
53564 Additional Information 48767-8
53565 Specimen 31208-2
53566 Source 31208-2
53567 Released By 18771-6

Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Molecular Genetics: Biochemical Disorders Patient Information (T527)

3. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.