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HelpTest Code LAB1921 VLCAD Sequencing
Clinical System Name
VLCAD (ACADVL) Sequencing
Description
Very Long Chain Acyl-CoA Dehydrogenase Deficiency (VLCAD) is a treatable disorder of fatty acid metabolism caused by an inability to use very-long-chain fats for energy. It is caused by mutations in the ACADVL gene.
ACADVL gene sequencing is appropriate for:
- Infants with abnormal newborn screening results
- Infants with hypoglycemia, liver disease and cardiomyopathy
- Children with hypoglycemia, enlarged liver, muscle weakness & cramping with reddish-brown urine
Also available: Targeted Gene Variant Sequencing (LAB1915) - For targeted analysis of variants previously identified through clinical testing of a family member or research testing of the individual. Please review requirements and restrictions for testing.
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
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 (MUST specify source on requisition)
Preferred: 5µg
Minimum: 2µg
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: 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
| Specimen Type | Description |
Temperature |
Storage instructions |
| Whole blood | EDTA or ACD tube | Refrigerate | Molecular Genetics box in CPA refrigerator #2 |
| Extracted DNA | DNA aliquot tube | Refrigerate | Molecular Genetics box in CPA refrigerator #2 |
| Saliva | OGD-575/675 kit | Room temp | Place in CPA Cytogenetics room temp box |
Off-site collection: Refrigerate blood samples until ready to ship. Transport blood or DNA at room temperature via overnight shipping.
Stability
| Specimen Type | Temperature | Time |
|---|---|---|
| Whole blood | Room temp | 3-5 days |
| Whole blood | Refrigerated | 7 days |
| Extracted DNA | RT, refrig or frozen | stable |
| Saliva, ORAgene Dx OGD-575/675 | Refrig or room temp | up to 2 weeks |
Note: Whole blood samples > 7days may be submitted to be assessed by our lab for acceptability for testing.
Performing Laboratory
Seattle Children's Laboratory
Department
Department: Molecular Genetics Laboratory
Phone: 206-987-3872
Lab Client Services: 206-987-2617, labclientservices@seattlechildrens.org
Lab Genetic Counselor: LabGC@seattlechildrens.org
Lab Client Services: 206-987-2617
Lab Genetic Counselor: LabGC@seattlechildrens.org
Availability
| STAT | Performed | TAT |
|---|---|---|
| Contact lab | Monday - Friday | 4-6 weeks |
Follow-up testing requested based on Washington State Lab Newborn Screening Program referrals will be expedited.
Methodology
Method: Next Generation Sequencing technology using an Illumina NextSeq instrument. Target region includes coding exons and a minimum of 10 bp of flanking intron boundaries of the genes tested. Target enrichment performed using a custom Integrated DNA Technologies (IDT) Exome Hyb Panel v2.
Average coverage ~150x, depth of coverage for all target regions is at least 20x.
Limitations:
This testing is performed on an exome backbone with analysis restricted to the target gene. This method can detect single nucleotide variants (SNVs), small deletions, small insertions, and copy number variants in the regions targeted. Some regions cannot be efficiently captured due to sequence homology or sequence properties. This method will not detect large insertions and deletions, complex indels, structural variants (e.g. inversions, translocations), short tandem repeats, or other complex variants. Variants located outside of targeted regions will not be detected.
Based on validation studies, the bioinformatics pipeline showed precision and detection >99% for SNVs in regions with coverage greater than 20x and high mapping quality. Sensitivity for CNVs involving multiple genes is >99% and sensitivity for intragenic CNVs is >90%. Mosaic sequence variants present at <25% allele frequency may not be reliably detected, and detection sensitivity is dependent on the nature of the variant. The sensitivity of detection of mosaic copy number variants has not been evaluated.
Reference Range
Interpretive report will be provided. Variants are not reported if they are considered benign.
CPT Codes
81406
Requisition
Special Instructions
Links to: VLCAD Genetics Home Reference Entry , Very Long-Chain Acyl-Coenzyme A Dehydrogenase Deficiency GeneReviews
Clinical Utility
VLCAD is a treatable disorder of fatty acid metabolism caused by an inability to use very-long-chain fats for energy. Fatty acid metabolism occurs during prolonged fasting and/or periods of increased energy demands (fever, stress) when energy production relies increasingly on fat metabolism. Severe VLCAD can cause hypoketotic hypoglycemia, hepatomegaly, cardiomyopathy and arrhythmias, lethargy, and failure to thrive. The age of onset can be from early infancy to adulthood. Infants can present with hypoglycemia, liver disease, and cardiomyopathy. Children who present outside of the newborn period present with hypoglycemia, enlarged liver, and muscle weakness. Most patients who show symptoms in teen years or adulthood have periods of muscle weakness and cramping with reddish-brown urine. Full gene sequencing will identify greater than 98% of pathogenic variants in affected individuals. Carrier testing for biological family members is available once variants are known.