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Andersen-Tawil Syndrome/Long QT Syndrome via the KCNJ2 Gene

Order Options and Pricing
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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
KCNJ2 81403 81403,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
9163KCNJ281403 81403,81479 $990 Order Options and Pricing

EMAIL CONTACTS

Genetic Counselors

Geneticist

  • Chun-An Chen, PhD

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 platform).

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

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

For Sanger Sequencing click here.

Turnaround Time

3 weeks on average for standard orders or 2 weeks 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

Indications for Test

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

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 including 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, called Anderson-Tawil syndrome, occur in people who have an underlying variation in the KCNJ2 gene.

Anderson-Tawil syndrome (ATS), also called Andersen syndrome and Long QT syndrome 7,  is a disorder that causes episodes of muscle weakness (periodic paralysis), changes in heart rhythm (arrhythmia), prolonged QT interval and dysmorphic features (Davies et al. 2005).

Genetics

Andersen–Tawil syndrome is a rare genetic disorder that is inherited in an autosomal dominant pattern (Tristani-Firouzi et al. 2002). At least 50% of individuals diagnosed with ATS have an affected parent and up to 50% of cases are caused by de novo mutations. So far, KCNJ2 mutations found in ATS are missense/nonsense (88%), small deletion (7%) and gross insertions/deletion/ duplication (5%) (Human Gene Mutation Database).

KCNJ2, encoding the inward rectifier potassium channel 2 protein (Kir2.1), is an important  determinant of resting membrane potential and cell excitability (Plaster et al 2001). KCNJ2 is the only gene known to cause Anderson-Tawil syndrome.

Clinical Sensitivity - Sequencing with CNV PGxome

60% of Andersen–Tawil syndrome patients have a detectable pathogenic KCNJ2 mutation, while the genetic cause in the other 40% remains elusive (Kukla P 2014). Analytical sensitivity should be high because the majority of mutations reported are detectable by sequencing.

Approximately 5% of ATS cases are caused by a gross deletion or duplication (Human Gene Mutation Database).

Testing Strategy

This test provides full coverage of all coding exons of the KCNJ2 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
KCNJ2 600681
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Andersen Tawil Syndrome 170390

Related Tests

Name
Long QT Syndrome via the KCNJ5 Gene
Long QT Syndrome via the SCN4B Gene

Citations

  • Cerrone M. et al. 2012. Circulation. Cardiovascular genetics. 5: 581-90. PubMed ID: 23074337
  • Davies NP, Imbrici P, Fialho D, Herd C, Bilsland LG, Weber A, Mueller R, Hilton-Jones D, Ealing J, Boothman BR, Giunti P, Parsons LM, Thomas M, Manzur AY, Jurkat-Rott K, Lehmann-Horn F, Chinnery PF, Rose M, Kullmann DM, Hanna MG. 2005. Andersen-Tawil syndrome: new potassium channel mutations and possible phenotypic variation. Neurology 65: 1083–1089. PubMed ID: 16217063
  • Human Gene Mutation Database (Bio-base).
  • Human Gene Mutation Database (Bio-base).
  • Kukla P, Biernacka EK, Baranchuk A, Jastrzebski M, Jagodzinska M. 2014. Electrocardiogram in Andersen-Tawil syndrome. New electrocardiographic criteria for diagnosis of type-1 Andersen-Tawil syndrome. Curr Cardiol Rev 10: 222–228. PubMed ID: 24827800
  • Plaster NM. et al. 2001. Cell. 105: 511-9. PubMed ID: 11371347
  • Priori et al. 2004. PubMed ID: 15367556
  • Schwartz et al. 2001. PubMed ID: 11136691
  • Tristani-Firouzi M, Jensen JL, Donaldson MR, Sansone V, Meola G, Hahn A, Bendahhou S, Kwiecinski H, Fidzianska A, Plaster N, Fu Y-H, Ptacek LJ, Tawil R. 2002. Functional and clinical characterization of KCNJ2 mutations associated with LQT7 (Andersen syndrome). Journal of Clinical Investigation 110: 381–388. PubMed ID: 12163457

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

If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.

Specimen Types

Specimen Requirements and Shipping Details

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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ORDER OPTIONS

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