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Tuberous Sclerosis Complex Panel (TSC1, TSC2)

Test code(s) 38661

Question 1. What is the clinical application of this test?

This test is used to identify individuals with autosomal dominant tuberous sclerosis complex (TSC). It detects single-nucleotide variants, deletions, and duplications in the TSC1 and TSC2 genes, which encode the tumor suppressor proteins: hamartin and tuberin, respectively.Sample reports and information regarding the specific variants analyzed for each gene are available on our website QuestHereditaryCancer.com.

Question 2. The gene mutation in this individual’s family is known. What other test might be appropriate?

If a familial mutation has been detected by sequencing or deletion/duplication studies, the Hereditary Cancer Single Site(s) test (test code 93945) may be considered. Official test results of the family member must be available for laboratory review. For more information, please visit our website QuestHereditaryCancer.com. To discuss a family history with a Quest Diagnostics genetic counselor, please call Quest Genomics Client Services at 1.866.GENE.INFO (1.866.436.3463).

Question 3. What are the clinical indications for this testing?

Testing may be indicated for individuals with a suspected diagnosis of TSC but not enough features to confirm a clinical diagnosis. A clinical diagnosis is confirmed for individuals with either 1 major clinical feature or 2 or more minor features1:

Major features

  • Angiofibromas (≥3) or fibrous cephalic plaque
  • Cardiac rhabdomyoma
  • Cortical dysplasias, including tubers and cerebral white matter migration lines
  • Hypomelanotic macules (3 to >5 mm in diameter)
  • Lymphangioleiomyomatosis (LAM)
  • Multiple retinal nodular hamartomas
  • Renal angiomyolipoma
  • Shagreen patch
  • Subependymal giant cell astrocytoma (SEGA)
  • Subependymal nodules (SENs)
  • Ungual fibromas (≥2)

Minor features

  • "Confetti" skin lesions (numerous 1- to 3-mm hypopigmented macules scattered over regions of the body such as the arms and legs)
  • Dental enamel pits (>3)
  • Intraoral fibromas (≥2)
  • Multiple renal cysts
  • Nonrenal hamartomas
  • Retinal achromic patch

Informed consent following genetic counseling is strongly recommended.

Question 4. Whom can I ask for help regarding a specific case?

For more information or to discuss a family history with a Quest genetic counselor, please call Quest Genomics Client Services at 1.866.GENE.INFO (1.866.436.3463).

Question 5. When is the right time to pursue this test?

The right time is different for every individual. An individual’s current medical status, personal experience with TSC, treatment or screening plan, and general readiness for genetic information all influence the decision to be tested. Having an open dialogue with individuals about these topics can assist with shared decision-making.

Question 6. How do I know if insurance will cover this testing?

Upon receipt of a fully completed order, our team will verify coverage with your patient’s healthcare insurance plan and estimate their likely out-of-pocket responsibility. If your patient’s estimated responsibility is over $100, we will notify you and/or your patient prior to test initiation to discuss options for continuation or cancellation of the test. Please note that orders lacking complete information will not be processed.

Question 7. How quickly can I expect results?

On average, results will be completed 14 to 21 days after receipt of the sample in the laboratory if the family history form and order are complete and the health plan does not require preauthorization. Turnaround time may vary based on delays caused by incomplete orders or insurance authorizations.

Question 8. What does a positive result mean?

Individuals with a positive result have a pathogenic or likely pathogenic variant detected in the TSC1 or TSC2 gene and a diagnosis of autosomal dominant TSC. A positive result does not mean that an individual has all the clinical features of TSC or will definitely develop them in the future. Specific risk information will be provided in the result report, and you can visit our website at QuestHereditaryCancer.com for more information.  

Additionally, Tuberous Sclerosis Complex International has published clinical consensus guidelines for surveillance and management of individuals with TSC.2

Question 9. What does a negative result mean?

A negative result means that a pathogenic or likely pathogenic variant was not detected in the TSC1 or TSC2 genes. For more information regarding specific genetic variants analyzed in this assay, please refer to the methods and limitations section of the genetic testing report. Clinical diagnostic criteria are available if an individual is still suspected of having a diagnosis of TSC in the context of a negative genetic testing result.1,2

Question 10. What does a variant of uncertain clinical significance (VUS) result mean?

A VUS result means that the variant has not been previously described in the literature or that the clinical significance is unclear based upon currently available evidence. Medical management decisions should be based on personal and family history. Family studies may help to learn more about the clinical significance of this variant. The classification and interpretation of the variant(s) identified reflect the current state of Quest’s understanding at the time of the report. Variant classification and interpretation are subject to professional judgment and may change for a variety of reasons including, but not limited to, updates in classification guidelines and availability of additional scientific and clinical information. It is important to check in with the laboratory annually for variant updates because new information regarding the variant and classification may become available over time. Please visit QuestDiagnostics.com/VariantIQ for information about variant classification. If you have questions, please call Quest Genomics Client Services at 1.866.GENE.INFO (1.866.436.3463) to speak with a genetic counselor.

References

  1. Northrup H, Koenig MK, Pearson DA, et al. Tuberous sclerosis complex. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews® [Internet]. University of Washington, Seattle;1993-2020. Accessed January 17, 2020. https://www.ncbi.nlm.nih.gov/books/NBK1220/
  2. Krueger DA, Northrup H; International Tuberous Sclerosis Complex Consensus Group. Tuberous sclerosis complex surveillance and management: recommendations of the 2012 International Tuberous Sclerosis Complex Consensus Conference. Pediatr Neurol. 2013;49(4):255–265. doi:10.1016/j.pediatrneurol.2013.08.002
This FAQ is provided for informational purposes only and is not intended as medical advice. A clinician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
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