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Long QT Syndrome via the SCN4B Gene

Summary and Pricing

Test Method

Exome Sequencing with CNV Detection
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
8765 SCN4B 81479 81479,81479 $890 Order Options and Pricing
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
8765SCN4B81479 81479(x2) $890 Order Options and Pricing

Pricing Comments

Our favored testing approach is exome based NextGen sequencing with CNV analysis. This will allow cost effective reflexing to PGxome or other exome based tests. However, if full gene Sanger sequencing is desired for STAT turnaround time, insurance, or other reasons, please see link below for Test Code, pricing, and turnaround time information. If the Sanger option is selected, CNV detection may be ordered through Test #600.

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing backbone).

Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing backbone).

The Sanger Sequencing method for this test is NY State approved.

For Sanger Sequencing click here.

Turnaround Time

18 days on average for standard orders or 13 days on average for STAT orders.

Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.

Targeted Testing

For ordering sequencing of targeted known variants, go to our Targeted Variants page.

EMAIL CONTACTS

Genetic Counselors

Geneticist

  • Chun-An Chen, PhD

Clinical Features and Genetics

Clinical Features

Long QT syndrome (LQTS) is a heritable channelopathy characterized by an exceedingly prolonged cardiac repolarization that may trigger ventricular arrhythmias (torsade de pointes), recurrent syncopes, seizure, or sudden cardiac death (SCD) (Cerrone et al. 2012). The incidence of LQTS has been estimated between 1 in 2500 and 1 in 7000 in the general population. LQTS can manifest with syncope and cardiac arrest that is commonly triggered by adrenergic stress, often precipitated by emotion or exercise. Roughly 10% to 15% of patients experience symptoms at rest or during the night (Schwartz et al. 2001). The mean age of onset of symptoms is 12 years, and earlier onset usually is associated with a more severe form of the disease (Priori et al 2004). Inherited LQTS occurs due to mutations in multiple genes such as KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), ANK2(LQT4), KCNE1 (LQT5), KCNE2 (LQT6), KCNJ2(LQT7), CACNA1C(LQT8), CAV3(LQT9), SCN4B(LQT10), AKAP9(LQT11), SNTA1(LQT12) and KCNJ5 (LQT13), but it can also be acquired (acquired LQTS), usually as a result of pharmacological therapy. A small percentage of cases of LQTS occur in people who have an underlying variation in the SCN4B gene.

Genetics

Pathogenic variants in SCN4B are associated with Long QT syndrome type 10 (LQT10) and are inherited in an autosomal dominant manner (Yu et al. 2003). The SCN4B gene is composed of five exons (228 amino acids) on Chromosome 3p23. Sodium channels consist of α subunits and β subunits, which could be classified as “Voltage-gated” or “ligand-gated” based on the triggers. SCN4B encodes protein Navβ4, a β4 subunit of the voltage-gated sodium channel. Navβ4 is expressed primarily in excitable tissues, including neuronal, muscular and cardiac tissues (Maier et al. 2004). The β4 subunit is covalently associated with sodium channel α subunit via a disulfide bond to constitute a functional ion channel complex. The β4 subunit modulates the channel's gating kinetics and voltage dependence. Pathogenic variants in SCN4B cause a dramatic eight-fold increase in the late sodium current, which interfere with cardiac electrophysiology (Meadows et al. 2005; Medeiros-Domingo et al. 2007). So far, all causative variants reported in SCN4B are missense (Human Gene Mutation Database).

Clinical Sensitivity - Sequencing with CNV PGxome

Up to 70 % of patients with clinical diagnosis of Long QT syndrome have identifiable pathogenic variants (Beckmann et al. 2013). The majority of LQTS cases are caused by pathogenic variants in one of three genes: KCNQ1, KCNH2 and SCN5A. Approximately 5% of LQTS pathogenic variants were contributed together by following genes: ANK2, KCNE1, KCNE2, KCNJ2, CACNA1C, CAV3, SCN4B, AKAP9, SNTA1 and KCNJ5 (Lieve et al. 2013; Kapplinger et al. 2009).

To date, no pathogenic large deletions or duplications in the SCN4B gene have been reported (Human Gene Mutation Database).

Testing Strategy

This test provides full coverage of all coding exons of the SCN4B gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as >20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).

Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).

Indications for Test

All patients with symptoms suggestive of Long QT syndrome are candidates for this test.

Gene

Official Gene Symbol OMIM ID
SCN4B 608256
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Long QT Syndrome 10 AD 611819

Related Tests

Name
Comprehensive Cardiology Panel
Sudden Cardiac Arrest Panel

Citations

  • Beckmann B-M, Wilde AAM, Kääb S. 2013. Clinical utility gene card for: long-QT syndrome (types 1-13). Eur. J. Hum. Genet. 21: PubMed ID: 23511927
  • Cerrone M. et al. 2012. Circulation. Cardiovascular genetics. 5: 581-90. PubMed ID: 23074337
  • Human Gene Mutation Database (Bio-base).
  • Kapplinger JD, Tester DJ, Salisbury BA, Carr JL, Harris-Kerr C, Pollevick GD, Wilde AAM, Ackerman MJ. 2009. Spectrum and prevalence of mutations from the first 2,500 consecutive unrelated patients referred for the FAMILION long QT syndrome genetic test. Heart Rhythm 6: 1297–1303. PubMed ID: 19716085
  • Lieve KV, Williams L, Daly A, Richard G, Bale S, Macaya D, Chung WK. 2013. Results of genetic testing in 855 consecutive unrelated patients referred for long QT syndrome in a clinical laboratory. Genet Test Mol Biomarkers 17: 553–561. PubMed ID: 23631430
  • Maier SKG, Westenbroek RE, McCormick KA, Curtis R, Scheuer T, Catterall WA. 2004. Distinct subcellular localization of different sodium channel alpha and beta subunits in single ventricular myocytes from mouse heart. Circulation 109: 1421–1427. PubMed ID: 15007009
  • Meadows LS, Isom LL. 2005. Sodium channels as macromolecular complexes: implications for inherited arrhythmia syndromes. Cardiovasc. Res. 67: 448–458. PubMed ID: 15919069
  • Medeiros-Domingo A, Kaku T, Tester DJ, Iturralde-Torres P, Itty A, Ye B, Valdivia C, Ueda K, Canizales-Quinteros S, Tusié-Luna MT, Makielski JC, Ackerman MJ. 2007. SCN4B-encoded sodium channel beta4 subunit in congenital long-QT syndrome. Circulation 116: 134–142. PubMed ID: 17592081
  • Priori et al. 2004. PubMed ID: 15367556
  • Schwartz et al. 2001. PubMed ID: 11136691
  • Yu FH, Westenbroek RE, Silos-Santiago I, McCormick KA, Lawson D, Ge P, Ferriera H, Lilly J, DiStefano PS, Catterall WA, Scheuer T, Curtis R. 2003. Sodium channel beta4, a new disulfide-linked auxiliary subunit with similarity to beta2. J. Neurosci. 23: 7577–7585. PubMed ID: 12930796

Ordering/Specimens

Ordering Options

We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.

myPrevent - Online Ordering

  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
  • PGnome sequencing panels can be ordered via the myPrevent portal only at this time.

Requisition Form

  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.

For Requisition Forms, visit our Forms page


Specimen Types

Specimen Requirements and Shipping Details

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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ORDER OPTIONS

View Ordering Instructions

1) Select Test Method (Backbone)


1) Select Test Type


2) Select Additional Test Options

STAT and Prenatal Test Options are not available with Patient Plus.

No Additional Test Options are available for this test.

Note: acceptable specimen types are whole blood and DNA from whole blood only.
Total Price: $
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