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Long QT Syndrome via the KCNJ5 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
KCNJ5 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
8889KCNJ581479 81479,81479 $990 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 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

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), KCN J2 (LQT7), CACNA1C (LQT8), CAV3 (LQT9), SCN4B (L QT10), 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 pathogenic variant in the KCNJ5 gene.

Genetics

Long QT syndrome type 13 (LQT13) is caused by loss-of-function mutation in KCNJ5 and is inherited in an autosomal dominant manner. The protein encoded by KCNJ5 is an integral membrane protein, inward-rectifier type potassium channel and is controlled by G-proteins (Yang et al. 2010). Neuronal and cardiac G-protein-coupled inward rectifier potassium (Girk) channels are homo- and hetero-tetrameric complexes formed by subunits encoded by four genes named Girk1–4 /Kir3.1–4/KCNJ3, KCNJ6 , KCNJ9 and KC NJ5. Cardiac IKACh channels are complexes consisting of Girk1 (KCNJ3) and Girk4 (KCNJ5) (Wickman et al. 1999). IKACh channels are predominantly expressed in the sinoatrial node, atria, and atrioventricular node. Biochemical and genetic studies have demonstrated that IKACh plays an important role in both parasympathetic slowing of the heart rate and repolarization of atrial action potentials (Mesirca et al. 2013). Besides Long QT syndrome, pathogenic variants in KCNJ5 also cause Familial Hyperaldosteronism (Human Gene Mutation Database). To date, all reported pathogenic variants are missense variants.

Clinical Sensitivity - Sequencing with CNV PGxome

Up to 70 % of patients with a 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. Pathogenic variants in the following genes: ANK2, KCNE1, KCNE2, KCNJ2, CACNA1C, CAV3, SCN4B, AKAP9, SNTA1 and KCNJ5 together cause about 5% of LQTS (Lieve et al. 2012; Kapplinger et al. 2009).

To date, no gross deletions or duplications have been reported in KCNJ5 (Human Gene Mutation Database).

Testing Strategy

This test provides full coverage of all coding exons of the KCNJ5 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
KCNJ5 600734
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Long QT Syndrome 13 AD 613485

Related Tests

Name
Andersen-Tawil Syndrome/Long QT Syndrome via the KCNJ2 Gene
Catecholaminergic Polymorphic Ventricular Tachycardia and Long QT Syndrome via the CALM1 Gene
Comprehensive Cardiology Panel
Long QT Syndrome and Jervell and Lange-Nielsen Syndrome via the KCNE1 Gene
Long QT Syndrome via the KCNE2 Gene
Long QT Syndrome via the KCNH2 Gene
Long QT Syndrome via the SCN4B Gene
Long QT Syndrome via the SNTA1 Gene

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
  • Mesirca P, Marger L, Toyoda F, Rizzetto R, Audoubert M, Dubel S, Torrente AG, Difrancesco ML, Muller JC, Leoni A-L, Couette B, Nargeot J, Clapham DE, Wickman K, Mangoni ME. 2013. The G-protein-gated K+ channel, IKACh, is required for regulation of pacemaker activity and recovery of resting heart rate after sympathetic stimulation. J. Gen. Physiol. 142: 113–126. PubMed ID: 23858001
  • Priori et al. 2004. PubMed ID: 15367556
  • Schwartz et al. 2001. PubMed ID: 11136691
  • Wickman K, Krapivinsky G, Corey S, Kennedy M, Nemec J, Medina I, Clapham DE. 1999. Structure, G protein activation, and functional relevance of the cardiac G protein-gated K+ channel, IKACh. Ann. N. Y. Acad. Sci. 868: 386–398. PubMed ID: 10414308
  • Yang Y, Yang Y, Liang B, Liu J, Li J, Grunnet M, Olesen S-P, Rasmussen HB, Ellinor PT, Gao L, Lin X, Li L, Wang L, Xiao J, Liu Y, Liu Y, Zhang S, Liang D, Peng L, Jespersen T, Chen YH. 2010. Identification of a Kir3.4 mutation in congenital long QT syndrome. Am. J. Hum. Genet. 86: 872–880. PubMed ID: 20560207

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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