Download - Session Three: Genetic Testing Process
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Genomics for the Child Neurologist:
Genetic Testing Process
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Facilitator(s)
Name• Expertise• Credentials
• Titles
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Re-Cap: Evaluation & Testing Decisions
Narrow the differential
Select appropriate tests
Develop a family testing strategy
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Workshop Three:Genetic Testing Process
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Identify benefits, limitations, risks
Provide informed consent
Order testing appropriately
Take time to prepare for outcomes of testing
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Evaluation & Testing DecisionsLearning Objectives
1. Use data to identify limitations of genetic testing
2. Weigh the benefits and risks of testing in the patient’s individual scenario
3. Provide pre-test education and counseling
4. Develop a protocol for ordering appropriate testing
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2 yo male
History of febrile and afebrile seizures
Clinical Scenario: James
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James2 y
Seizures
Key
Seizures
SeizuresD. 10
accident
James Family History
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Evaluations and unique features point toward Dravet syndrome
Differential Diagnosis includes:
•Severe myoclonic epilepsy of infancy (SMEI, or Dravet syndrome)•Pyridoxine, B6 and Folic acid related seizures•Biotinidase deficiency
•Autosomal dominant nocturnal frontal lobe epilepsy
•Simple febrile seizures
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Overview Dravet Syndrome
Features:•Severe myoclonic epilepsy of infancy•Cognitive decline over time
Genetics: •30-80% cases associated with a variant in SCN1A gene
Inheritance: •Typically de novo (depends on phenotype)•When inherited, autosomal dominant with significant intra-familial variable expression
Management: •Difficult to control•Anticonvulsant drugs and ketogenic diet may reduce seizure frequency
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Identify benefits, limitations, risks
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Step 1: Assess ability of the test to detect variants in your patient’s population
What is the yield of genetic testing in a child with severe myoclonic epilepsy?
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30-80% of individuals with Dravet have a detectable mutation in SCN1A
SCN1A
Other, unknown
genes
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Step 2: Assess the ability of a variant to predict outcomes
What could the detection of a variant tell the clinician about future outcomes for the patient and risk for family members?
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Variable expression limits prognostic value and family risk counseling
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Step 3: Anticipate other results
How would you use a negative result?
What would you do with a variant of uncertain significance?
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Negative genetic test doesn’t rule out disease in a symptomatic individual
SCN1A
Other, unknown
genes
SCN1APortion of variants
missed by test•Technology limitations•Test selected
No variants detected
Not tested
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Step 3: Anticipate other results
How would you use a negative result?
What would you do with a variant of uncertain significance?
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A VUS is uninformative and shouldn’t be used clinically
Not seen in any previous patient
OR
Contradictory reports in other individuals
AND/OR
Unknown effect on gene function
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Step 4: Identify and weigh risks
What are the general risks associated with genetic testing, and which ones apply to James?
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General risks of genetic testing
• Discrimination
• Family impact and privacy• Psychosocial coping and adaptation
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Genetics Information Non-discrimination Act
(GINA) affords some protections
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How would you discuss the risks, benefits, and limitations of testing?
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Balance benefits, limitations, and risks in the context of the patient and family
Benefits• End diagnostic odyssey• Clarify reproductive risk• Refine differential
Limitations• Variable expression limits predictions• Uninformative negative• Uninformative VUS
Risks • Clinical uncertainty• Psychosocial impact
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Summary: Steps To Assessing Limitations and Risks
Step 1: Assess likelihood of detecting a variant
Step 2: Assess ability of a variant to predict outcomes
Step 3: Anticipate other results
Step 4: Identify benefits and risks
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Provide Informed Consent
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What do you do for pre-test counseling currently?
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Informed consent paves the way for results disclosure
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Small Group Practice
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7 yo female
Developmental delayHypotoniaDysmorphic features
Clinical Scenario: Suzie
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What are your initial counseling messages?
Step 1: Communicate goals of microarray testing
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Keep initial messages simple
A genetic test
because… We’ll use it to…
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Step 2: Check understanding and assess family expectations
What might Suzie’s family be expecting from results? How would you find out?
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Families want explanations and guidance
Did I cause it?
What will the future hold?
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Step 3: Set realistic expectations
What additional information does the family need to be prepared for the various possible outcomes?
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Reinforce limitations and risks; and discuss the process
Uncertainty is possible…
You’ll get results in…
Unexpected results are possible….
We might need more
tests.
Genes are…
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Did you adequately prepare the family for this outcome?
Patient Name: Suzie HubbardTest Performed: SNP Array AnalysisIndication: Developmental Delay
Result:Normal Dosage; Long contiguous regions of homozygosity, see interpretation.
Interpretation:Copy number analysis was within normal limits, but there are extended contiguous regions of allele homozygosity (>10Mb) observed in multiple chromosomes that suggests limited outbreeding (possible consanguinity). Recommendations: Consanguinity increases the chance for rare autosomal recessive disorders. Clinical correlation and genetic counseling are recommended.
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Prepare the family for unexpected results, especially when family information is lacking
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Summary: Steps to Pre-test Communication
• Step 1: Outline goals
• Step 2: Assess family motivations and aims
• Step 3: Set expectations
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Consider referral or consult for pre-test counseling
When to consult/refer:
•Lack of time •Low-literacy•Emotional responses•Family undecided
•Data is weak with unclear benefits
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Order Testing Appropriately
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What is your experience with ordering genetic tests?
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Genetic Testing Logistics
Finding a lab
Cost and insurance
Prepare the sample and forms
Reporting practices
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Finding a Lab
Referral Lab
http://www.ncbi.nlm.nih.gov/gtr
Genetics Specialist
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Some labs verify
insurance
Genetic testing is medically necessaryDr. Susan Smith
Insurance and Cost
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Preparing the sample and forms
Genetic Testing Requisition
Clinical History_____________
Family History_____________
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Reporting Practices Vary
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Genetic testing can get complicated
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Summary: Genetic Testing Process
• Use data to assess limitations, benefits and risks
• Anticipate potential results and how you will use them
• Set family expectations
• Expect a higher maintenance ordering process
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Next steps
• Refer or consult with genetics
• Interpret results in the clinical context• Communicate with families about the
results• Develop a management plan based on
the genetic data
To be discussed in workshop 4
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Homework/Practice
•Practice assessing limitations, benefits and risks and composing pre-test counseling messages for
– Ataxia telangiectasia
•Use the informed consent checklist and talking points with at least one patient before the next workshop. Be prepared to share your experiences with the group.
www.nchpeg.org/neuro
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Thank you!
[facilitator contact information]