Emerging issues: Cost-effective PGD

Renwick, P.
May 2010
Reproductive BioMedicine Online (Reproductive Healthcare Limited;May2010 S1 Supplement, Vol. 20, pS2
Academic Journal
Aim: There is increasing demand on PGD centres with requests for rapid delivery of new genetic tests. Our PGD centre aims to provide accurate and robust tests at minimal cost for individual patients or NHS funding bodies. We introduced preimplantation genetic haplotyping (PGH) in 2006, and have now carried out sufficient cycles to assess the overall costs of this approach. Method: PGD requires tests that work with only a single DNA template as starting material. WGA turns this single template into millions, allowing the use of standard DNA tests. Any ADO is overcome by using indirect linkage analysis with multiple markers (microsatellites or SNPs). In comparison to biallelic SNPs, relatively few multi-allelic microsatellite markers are required to create informative haplotypes. In addition, microsatellite markers target analysis to the region of interest only, reducing incidental findings which would deplete embryos suitable for transfer . Panels of microsatellite markers for the gene of interest are selected and multiplexed tagged PCR developed on standard DNA. For each couple, family members of known status are tested to identify the alleles segregating with the disease. For the PGD cycle, DNA from single biopsied blastomeres undergoes PGH to determine the genetic status of each embryo. Results: It requires ~30 working hours to design and test a set of primers for a new PGH assay at a cost of ~£1000. Once a PGH test is designed, this test can be used for all couples requesting PGD for that disease. If only 1 cycle is performed (assume 7 embryos) the cost is £150 per embryo (including PCR costs), but this cost falls progressively as further cycles for the same disease are carried out. For instance, for cystic fibrosis couples at our centre, >500 embryos have been tested at an overall cost of £10 per embryo. Not all requests are amenable to haplotyping, such as those with genes near telomeres or those with adjacent recombination hotspots, only 2 out of 88 diseases were unsuitable for PGH. Established tests are suitable for >95% of couples. We have applied this approach for 218 PGD cycles, with a clinical pregnancy rate / OR of 33%. Conclusion: PGH using microsatellite markers is a low-cost and effective strategy, providing affordable PGD testing for couples at risk of transmitting single gene disorders.


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