Scottish Preimplantation Genetic Diagnosis Service

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Scottish Preimplantation Genetic Diagnosis Service

• Susan Glassford,
• Medical Genetics,Yorkhill, Glasgow

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Preimplantation Genetic Diagnosis

• Alternative to conventional PND for couples
  with a significant risk of transmitting a serious
  genetic disorder to their offspring
• both partners carry the same autosomal recessive
  genetic disorder
• female partner carries an X-linked disorder
• one partner carries chromosomal rearrangement

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Preimplantation Genetic Diagnosis

• Genetic diagnosis of a single cell removed from
  an early embryo created by standard IVF
  techniques.
• FISH or PCR techniques for diagnosis.
• Allows transfer to the uterus of unaffected
  embryos.
• Significantly reduces the risk of transmitting a
  genetic disorder while providing a realistic
  chance of the birth of a healthy baby.

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Scottish PGD service

• 2001
• license issued by Human Fertilisation and
  Embryology Authority (HFEA) to Medical Genetics,
  Yorkhill and Assisted Conception Unit,GRI to
  provide joint PGD service
• embryo sexing for specified X-linked genetic
  conditions
• -DMD, Hunter syndrome, X-Linked hydrocephalus
• provide PGD for carriers of chromosome
  rearrangements
• -translocations, deletions, inversions
• 2005
• obtained funding from NSD to provide a national
  (Scottish) PGD service

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PGD procedure Stimulation/Retrieval/Fertilization

• controlled ovarian stimulation
• oocyte retrieval
• fertilization (standard IVF/ICSI)

2 pronuclei
4 cell embryo
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PGD procedure Cleavage stage biopsy (day 3)
biopsied blastomere
blastomeres
zona drilling
aspiration of blastomere
Courtesy of Paul Mitchell, ACS Suite, GRI
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PGD procedure FISH diagnosis

• Embryo sexing
• 3 probe mix
• chromosome X chromosome Y chromosome 18

male nucleus
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PGD procedure FISH diagnosis

• Chromosomal rearrangements
• 3 probe mix
• 4q telomere 16q telomere 16 centromere

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PGD procedure embryo transfer

• Transfer of unaffected embryos on day 4
• X-linked disorders
• -transfer of female embryos (except IP)

female transferrable
male non-transferrable
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PGD procedure embryo transfer

• Transfer of unaffected embryos on day 4
• Chromosome rearrangements
• -embryos with a normal/balanced signal pattern
• t(416) carrier 4qtel 16qtel CEP 16

Unbalanced
normal/balanced - transferrable
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Non-transferred embryos

• processed and analysed for confirmation of
  biopsy diagnosis
• assess FISH error rate (false ve/false ve)

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Cycle Data 2002 - 2008
Indication
No. of cycles started (49)
Chromosomal rearrangements 26 53 Reci
procal 17 Robertsonian 6 Deletions 3 X-linked
disorders 20 41 DMD 6 Adrenoleukodystrophy 2 Hun
ters syndrome 2 Incontinenta pigmenti 2 Fragile
X 2 Alports syndrome 1 Barth syndrome 1 Lesch-Nyan
syndrome 1 X-linked hydrocephalus 1 X-linked
HMSN 1 X-linked LPD 1 Other 3 6 Recurrent
trisomy 21 3
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Sex determination cycles
Total no. of cycles 20 Cycles to
OR 19 Cycles to biopsy 17 No of embryos
biopsied 115 Successfully biopsied 102 Diagnose
d (conclusive) 92 Transferrable 30 Tranferred 2
2 Cycles to ET 15 hCG positive 4 Positive
heartbeat 3 Clinical pregnancy rate ( per
OR/ET) 21/27 (19/25, ESHRE) Livebirth rate( per
OR/ET) 16/20
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Chromosomal rearrangements
Total no. of cycles 29 Cycles to OR 23 Cycles to
biopsy 22 No of embryos biopsied 110 Successfully
biopsied 104 Diagnosed (conclusive) 93 Transfe
rrable 30 Tranferred 22 Cycles to ET 17 hCG
positive 6 Positive heartbeat 3 Clinical
pregnancy rate ( per OR/ET) 26/35 (16/25,
ESHRE) Livebirth rate ( per OR/ET) 13/18
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Data Summary 2002-2008
Cycles started 49 Cycles reached
retrieval 42 Cycles reached biopsy 39 Cycles with
transferable result 32 Cycle that achieved
pregnancy 10 Cycles that resulted in
livebirth 6 Pregnancy rate ( per
OR/perET) 24/31 Livebirth rate ( per OR/per
ET) 14/19
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Non-transferred embryos (sex determination)
Embryos for follow up 111 Normal at biopsy
37 35 gave follow up result - sex confirmed 2
failed Abnormal at biopsy 26 15 confirmed as
abnormal 6 normal (3 females ,3 males) 5
failed/inconclusive Failed/Inconclusive at biopsy
18 13 normal (5 females, 8 males) 4 abnormal
1 fail
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Non-transferred embryos (chromosomal
rearrangements)
Embryos for follow up 84 Normal/balanced at
biopsy 6 5 confirmed 1 failed Abnormal at
biopsy 65 45 confirmed 6 normal/balanced 14
failed Failed/inconclusive at biopsy 13 5
normal/balanced 5 abnormal 3 failed
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FISH error rates
Normal (biopsy)/Abnormal (follow up)
False ve () Embryo sexing 3.9
3 chaotic males not viable 1 female, mosaic
monosomy 18 - ? viable Chromosomal rearrangements
0 Abnormal (biopsy)/Normal (follow up)
False ve () Embryo sexing
5.8 3 males , 3 females Chromosomal
rearrangements 5.7 6 normal/balanced
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Summary

• reduction in FISH error rate (false ve)
• pregnancy rates (per OR/ET) comparable with
  recently published ESHRE data (Jan 2008)
• service to operate to funding capacity (30 cycles
  per year)