Also known as: LQT syndrome, LQTS, Romano-Ward syndrome (RWS), Jervell Lange-Nielsen syndrome (JLNS)
Familial - Cardiac
Use of test
Long QT syndrome (LQTS) can be an acquired or a familial disorder.
The familial form of the disease is due to mutations in any one of a number of genes. A mutation in one copy of such a gene can cause an autosomal dominant mode of inheritance (Romano-Ward syndrome).
LQTS can also be due to mutations in both copies of some of these genes, causing autosomal recessive LQTS (Jervell and Lange-Nielsen syndrome). The autosomal recessive form of the disease is associated with congenital deafness.
The diagnosis of LQTS is made on the basis of clinical and electrocardiographic findings. Genetic testing is not necessary to make this diagnosis.
This test result has implications regarding the aetiology of LQTS in an individual, and the risk of LQTS and related disorders in a patient's relatives.The interpretation of the result may be dependent on the family history and the interpretation of other studies.
A pathogenic mutation can be found in approximately 70% of patients with a clinical diagnosis of LQTS.
In an affected person with a clinical diagnosis of LQTS, the presence of a pathogenic mutation confirms the diagnosis of familial LQTS and may provide additional information regarding management and the risk of cardiac and non-cardiac manifestations in relatives. The identification of a mutation does not necessarily alter the management of the index patient. The absence of a pathogenic mutation in such a patient does not exclude the diagnosis of LQTS.
In an unaffected person from a family with confirmed genetic diagnosis of LQTS, the presence of the family's mutation may indicate an increased risk of developing LQTS, and close clinical follow-up may be warranted. The interpretation of such results depends on the particular gene and mutations. Pre-test genetic counselling is required.
This is an assay for heritable mutations. It may raise issues of ethics or consent that are different from most other investigations ordered in the routine care of a patient. Pre-test genetic counselling and written consent are required, and are provided through Sonic Genetics at no additional cost (see Cardiac genetic counselling for details).
This test can assist in making a diagnosis in an affected patient. It may also provide useful risk information for unaffected relatives. Testing unaffected people to provide risk information may require that the clinician comply with guidelines provided by professional and regulatory authorities regarding pre-test counselling and consent. In particular, national regulations stipulate that carrier testing of an unaffected child requires the laboratory to have evidence of pre-test counselling by a genetics professional and written consent. For advice or assistance, please contact us on 1800 010 447.
Consent managed by genetic counsellor.
Analysis of a gene panel for sequence abnormalities and deletions/duplications.
This test is provided by a Sonic Healthcare laboratory in Germany, Bioscientia.
For an updated list of genes included in the panel please click here.
Requesting the test
This test is usually requested by a cardiologist with experience in the genetic management of cardiac disease or a clinical geneticist.
2-5 mL blood in EDTA. Specimens may be collected by the requesting practitioner or at any Sonic Healthcare collection centre (see link below).
To help ensure the quality of the test, a genetic test should be done with a dedicated sample whenever possible i.e. a sample collected specifically for that test rather than a sample that is used for multiple tests.
We recommend that the patient or another adult check the labelling of request forms and sample tubes.
Please include a statement about family history (or absence of family history) of the disease in clinical details on referral form. If family history is present, please state relationship to patient.
This is the price for initial genetic testing of an affected person. Once a family's mutation is identified, targeted mutation analysis can be offered to family members; please contact Sonic Genetics on 1800 010 447 or at firstname.lastname@example.org regarding price and turn-around time.
This test is not rebated by Medicare. The laboratory assumes that the patient or client has provided informed financial consent for the test.