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Test Code LAB1870 LCHAD Sequencing

Clinical System Name

LCHAD/TFP (HADHA/HADHB) Sequencing

Synonyms

HADHA

HADHB

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency

Description

This test is appropriate for diagnostic confirmation in symptomatic individuals who have a presumptive diagnosis of LCHAD (Long-chain 3-hydroxyacyl-CoA deficiency).

 

Sequencing of the HADHA and/or HADHB gene is recommended for patients with a biochemical diagnosis of LCHAD or TFP deficiency, to provide molecular confirmation of the diagnosis. The most common pathogenic variant in isolated LCHAD deficiency is the p.E510Q (c.1528G>C) variant, accounting for an allele frequency of 87% in LCHAD deficient patients.

 

Full sequencing of HADHA and HADHB genes can be ordered sequentially or simultaneously, as appropriate. 

 

Also offered: targeted variant analysis for sequence variants previously identified through clinical testing of a family member or research testing of the individual.  Please provide copies of proband reports when requesting known mutation analysis for cases NOT performed by Seattle Children's Lab.

 

Sample Requirements

Note: For patients who have had a whole blood transfusion, wait 10 days post transfusion to draw for genetic testing. No wait time is necessary for blood or saliva collection if the patient received leuko-reduced red cells or plasma.

 

Specimen: Whole blood, cord blood

Container(s): Lavender/EDTA, Yellow/ACD A or B

Preferred Vol: 3 mL

Minimum Vol: 1 mL

 

Note: Heparin samples (Green tops) are unacceptable.

 

Specimen: Extracted DNA from EDTA blood

Minimum: 10µg

Note: : Isolation of nucleic acids for clinical testing must be performed in a CLIA-certified
laboratory or a laboratory meeting equivalent requirements as determined by the CAP
and/or the CMS. DNA concentration minimum 50 µg/mL; 260/280 ratio 1.70-2.00.

  

Specimen: Cultured cells

Acceptable:  Fibroblasts

Container(s): T-25 flasks

Preferred Vol: 2 flasks

 

Specimen: Saliva collected using Oragene Dx OGD-575/675 collection kit.

Container: Oragene Dx OGD-575/675 collection kit

IMPORTANT NOTE: Manufacturer instructions must be followed. The Oragene Dx OGD575/675 kit is not for children under 6 months. Contact Lab Client Services for more information or to obtain a kit 206-987-2617, labclientservices@seattlechildrens.org

Processing Instructions

Reject due to: Heparin

Spin: No

Aliquot: No

Temp: Refrigerate

Storage location: Molecular Genetics box in CPA refrigerator #2

 

Off-site collection: Refrigerate blood samples until ready to ship.  Transport all sample types at room temperature via overnight shipping.

Stability

Specimen Type Temperature Time
Cultured cells Room temp 3 days
Whole blood, extracted DNA Room temp 3-5 days
Whole blood, extracted DNA Refrigerated 7 days
Extracted DNA Frozen ok
Saliva, ORAgene Dx OGD-575/675 Room Temp 2 weeks

Note: Whole blood samples > 7days may be submitted to be assessed by our lab for acceptability for testing.

Availability

STAT Performed TAT
Contact lab Monday - Friday 2-3 weeks

 

Performing Laboratory

Seattle Children's Laboratory

Department

Department:  Molecular Genetics Laboratory

Phone: 206-987-3872

 

Lab Client Services: 206-987-2617

 

Lab Genetic Counselor: LabGC@seattlechildrens.org

CPT Codes

Test CPT
HADHA full gene seq 81406
HADHB full gene seq 81479 
HADHA targeted variant 81403
HADHB targeted variant 81479

 

 

Methodology

Method: Bi-directional sequencing of all exons and exon-intron boundaries

 

Limitations: This test will indentify >97% of sequence variants in the coding region and splice junctions. Pathogenic variants in the promoter region, large deletions, large duplications, or rare recombinant pathogenic variants may not be detected by this method.

Reference Range

Interpretive report will be provided

Requisition

Molecular Genetics

Special Instructions

Please indicate on the requisition which gene(s) are requested and sequencing preference (simultaneous or sequential)

 

Links to: LCHAD E-Medicine Review Article; LCHAD OMIM Entry
 

Clinical Utility

Long-chain-hydroxy Acyl-CoA dehydrogenase deficiency (LCHAD), and mitochondrial trifunctional protein deficiency (TFP) are disorders of long-chain fatty acid metabolism. They have overlapping clinical presentation that can include: feeding difficulties, lethargy, hypoglycemia, muscle weakness and liver dysfunction in infancy or early childhood. These symptoms are often triggered by prolonged fasting or viral infections. Muscle pain, breakdown of muscle tissue and peripheral neuropathy may occur later in childhood. These patients are at risk for complications such as life-threatening heart problems and sudden unexpected death. Carriers pregnant with affected fetuses can develop Acute Fatty Liver of Pregnancy (AFLP).

The mitochondrial trifunctional protein consists of 3 enzymes that work together to metabolize long-chain fats. Most patients have isolated deficiency of the LCHAD enzyme caused by pathogenic variants in the HADHA gene. A small portion of patients have defects in all three enzymes, called TFP deficiency, which is due to pathogenic variants in the HADHA or HADHB gene.

 

Full sequencing of HADHA and HADHB genes can be ordered sequentially or simultaneously, as appropriate.