provision of genetic counselling for patients with retinal dystrophy prof. graeme black, ms georgina...
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Provision of Genetic Counselling for Patients with
Retinal Dystrophy Prof. Graeme Black, Ms Georgina Hall
Depts. of Ophthalmology and Clinical Genetics,
Manchester
Causes of childhood blindness
Africa S America India
Genetic 21% 30% 30%
Intrauterine 7% 2% 10%
Perinatal 2% 2% 20%
Childhood 34% 37% 12%
Unknown 35% 30% 27%
Developed countries30-50% childhood visual handicap is genetic
Developing countries
In developed countries,
hereditary causes of blindness
are the most important cause of
childhood visual handicap
Retinitis pigmentosa
Symptoms• night blindness• constriction of peripheral
visual field • later loss of central vision.
Diagnosis • Progressive photoreceptor
dysfunction • undetectable / reduced ERGs……
rod-mediated responses more severely affected than cone-mediated (i.e. rod-cone dystrophy).
Retina • pigment in bone-spicule distribution.
Retinitis pigmentosa
1 in 2500
Genetic condition
Caused by single fault in one gene
Deoxyribonucleic acid (DNA) and chromosomes
46 chromosomes Human chromosomes
carry 20,000 to 30,000 genes
Genes and Inheritance
Chromosomes – 22 identical pairs (“Autosomes”)– 1 pair non- identical (“Sex
Chromosomes”)XX=Female XY=Male
Each chromosome carries 1 copy of gene (ie 2 copies of a gene per pair)
A genetic disorder is caused by
a single faulty gene
What is a gene?
Gene
Protein
Classification of RP Genetic
– Autosomal dominant 10-15%– X-linked 5-15%– Autosomal recessive 30-50%– Sporadic 20-50%
Onset– Birth : Leber congenital amaurosis– Childhood : many X-Linked, AR forms– Later onset: some AD forms
Retinal manifestations
(Symptoms or ERG define)
– Cone-rod dystrophy– Rod-cone dystrophy– Cone dystrophy– Rod dystrophy
Genes and RP
Confusing
– Faults in a large number of genes can cause RP and retinal degeneration
Retinal dystrophies Hugely variable
– onset outcome retinal findings– gene defect inheritance pattern
Gene analysis tells us there are a large number of different forms - ?100 -200
Majority unclassifiable clinically
Increasingly the precise genetic defect is known for many retinal degenerations…… or rather could be known
Genetics and Ophthalmology in Manchester
– 8 clinics per month– Run by clinical genetics alongside
ophthalmology– Coworkers present– Held in clinical genetics unit / eye hopsital– 4-6 pts/clinic
• Time• examine family members
– Letters to patient
Why have a genetic ophthalmic clinic at all?
Large group of uncommon disorders– Unified approach – Diagnosis– Investigation– Counselling / FH Issues
Pts referred for specialist opinion– ?correct diagnosis– ?geneticists cannot examine
Clinician’s Objectives
Diagnosis
Risk estimation to family members Screening requirements Information Support
Patient’s objectives (I think….) Treatment
Prognosis Understanding Risks to family members (Children)
– Prenatal diagnosis Presymptomatic diagnosis
Perhaps our objectives are different….
Genetic Counsellors
MSc genetic counselling Nurses
– Additional training in genetics and counselling 300 in the UK Professional body (AGNC) Register (GCRB)
– Code of ethics / conduct– Competency assessment
What is “genetic counselling”
Communication processComprehend medical informationAppreciate the hereditary impactFacilitate decision making (genetic testing, reproduction) in context of beliefs / family / cultural sensitvityMake best possible adjustment to genetic condition in family
Why do people request genetic counselling?
Diagnosis What is the cause? What will it mean for me? What are the risk to my children (other
family members) What screening / tests / treatments
available
Nature of genetic information
Patients may need to absorb a lot of new information that is often complex, abstract and difficult to grasp.
Rapid advances in understanding of genetic basis of eye conditions.
Heterogeneity – inheritance not clear cut.
Counselling issues
Over and above emotional impact of visual impairment (grief, loss)
Burden / guilt Coping with risk / uncertainty Difficult decisions Impact on relationships / family dynamics Family coping styles / beliefs around visual
impairment
X-linked retinitis pigmentosa
Boys affected late childhood / early teens Progressive No treatment Faulty gene on X chromosome Mothers are “carriers”
– Half daughters will be carriers– Half sons will be affected
XL Retinitis Pigmentosa
5
3
3
L dropped out of school, no exams Diagnosed XLRP aged 17 Anger and depression Isolated
M denied diagnosis. “It hasn’t come from me”
?guilt
XL Retinitis Pigmentosa
5
3
3
Am I a carrier?S
guilt
Sister S wanted to know if she was a carrier New baby son J How would she feel if she were a carrier? How would she feel about her new baby? Would it affect decisions about further
pregnancies?
XL Retinitis Pigmentosa
5
3
3
S
J
L
Testing children?
J has a 50% risk of being affected? Should he be tested? Would it affect parenting / schooling? Benefits to S – relieving uncertainty Benefits to J?
Meeting other family members
Individual needs / decisions Confidentiality Counselling issues evolve with time
Norrie’s disease
X-linked Blind at birth Additional risks
– 1/3 boys have learning difficulties– 1/3 boys develop deafness
Norrie disease
Chromosome 11p11.4NDP gene
Whole deletion inclNeighbouring MAO-A/B
Family
Tom
Shock It’s my fault How will I cope / my family
Sister about to start IVF treatment Burden of informing sister
Sister
50% chance she is carrier Able to offer a blood test Options
– Decide not to have a pregnancy– Continue with IVF (7/8 chance baby would
not have Norrie’s) or test a pregnancy– Have pre-implantation genetic diagnosis
Outcomes
Sister not a carrier, able to continue with IVF without anxiety
Tom doing extremely well. No learning difficulties or hearing problems. Very dedicated parents.
Future concerns that daughter could be a carrier. Will not offer testing until she can make her own choice.
Genetic testing for diagnosis:Can it be done?
Genes identified for wide range of retinal dystrophies are known
Genes able to besequenced
http://www.sph.uth.tmc.edu/Retnet/sum-dis.htm#D-graph
Molecular Genetic Testing
DNA sample (peripheral blood) Affected Individual / Obligate carrier
Identify sequence variant – not present in normal population
(monogenic disease) – In gene known to cause retinal disease
What is the Position in 2011?
Technological Advances mean tools
more powerful than ever
Many laboratories now offer diagnostic testing to the NHS
http://www.mangen.co.uk/molecular_eye_and_rare_disease.asp
Genetic testing for retinaldystrophies is possible and available
However testing is not universal
Where it is clearly required, testing is usually available
adRP
N = 1131
xlRP
n = 840
Why do patients require testing?Is the case for genetic testing persuasive?What is the evidence base?
Why develop genetic eye services?
Inequity of services Gene discovery Patient demand Treatment trials
Research to improve services
Regard study Programme Grant
Communication, accessibility Developing services for genetic
counselling and testing
Improving accessibility Hospital appointments by phone,
email Written information – large print,
email, braille, audio transcription Tactile genetic diagrams CCTV / software enlargement of
diagrams
Developing counselling services
Mainly anecdotal evidence of counselling needs of families with inherited eye disease
Requires robust research Evidence based MRC Framework for developing a
complex intervention
MRC framework
Phase 1– Modelling the intervention– Components
Phase 2– Exploratory trial
Randomised control trial
Aims
Design a patient led care model for counselling and testing
Develop evidence of patient benefit and “value” of improved counselling
Phase 1
“Modelling” Qualitative interviews with families and
healthcare professionals Snowballing Grounded theory
PPI Important to involve patients / users in design,
analysis and dissemination of research Regard Patient Advisory Group
– Patients / users / experts
– Leading charities (RNIB, BRPS, Guide Dogs, Macular Disease Society, NCBS, Genetic Alliance)
– Patients– VI researchers and social workers
PAG
Regular meetings Formal presentations (teaching, training, updates) Small group work
– Design methods Informal discussion Modify / improve design Regular email contact / updates and queries
– E.g. Review of patient information prior to Ethics application
– Publication of outputs included longer, more frequent meetings
Advantages of patient involvement
Motivation, extending knowledge base Relationships with pt support groups Focus work on improving patient care
– National patient perspective– Timely, fitting with patient needs
Collaboration– Genetic Alliance Route Maps, UK Vision strategy
workshop
Measuring benefit of genetic counselling
Outcome measuresInformation recall“satisfaction” surveyDepression / anxietyGenetic Empowerment scale
– Feelings around the condition, impact on family, hope for future, empowerment to make decisions
McAllister M et al, The Genetic Counseling Outcome Scale: a new patient-reported outcome measure for clinical genetics services Clinical Genet. 2011.
Phase 2
Exploratory trial– Feasibility of intervention– Pilot outcome measures / develop
estimates of effect size Economic “value”
– Willingness to pay– Economic modelling to understand cost
benefits of genetic testing
Conclusions
Retinal dystrophies important cause of VI in children/ young adults
Emotional need related to– VI– Family / genetic / treatment needs
Services patchily delivered Links to community support need to be
improved Research into delivery and impact required