Increased efficiency of preimplantation genetic diagnosis for infertility using "no result rescue"

Objective: To improve preimplantation genetic diagnosis (PGD) accuracy by using "no result rescue" (NRR) consisting of the reanalysis of dubious results with additional probes binding to a locus different from the one previously analyzed. Design: Prospective study of PGD cycles with and without reanalysis of inconclusive results. Setting: PGD laboratory. Patient(s): Patients undergoing PGD for infertility or Robertsonian translocations. Intervention(s): Nuclei from day 3 biopsied embryos were analyzed with fluorescence in situ hybridization for chromosomes X, Y, 13, 15, 16, 17, 18, 21, and 22. When inconclusive results were obtained, NRR was performed. In addition, 100 PGD cycles using NRR were matched to controls according to maternal age, previous failed cycles, number of zygotes, number of eggs, and date of retrieval. Main Outcome Measure(s): Determination of frequency of inconclusive results and error rate after use of additional probes. Comparison of frequency of inconclusive results with prior PGD results when NRR was not used. Assisted reproductive technology outcome was compared between PGD using NRR and controls not using PGD. Result(s): After analysis of 34,831 blastomeres from 34,225 embryos, 2,609 blastomeres (7.5%) showed inconclusive results. After NRR on those 2,609 blastomeres, the number of cells with inconclusive results was reduced to 3.1%, (P<.001). After the introduction of NRR, fluorescence in situ hybridization errors, measured as discrepancies between the PGD diagnosis and the analysis of the nonreplaced embryo, decreased from 13.6% to 4.7% (P<.001). PGD with NRR significantly improved implantation rates, from 20% to 31%, and reduced spontaneous abortions from 27% to 6%. Conclusion(s): The use of NRR has been proven to be a powerful tool to reduce the error rate and the frequency of inconclusive results in PGD, both parameters of high importance to assess quality of PGD laboratories. Indeed, these parameters are two of the few measurable criteria to measure PGD laboratories. In a parallel controlled study, PGD with NRR significantly improved implantation rates and reduced spontaneous abortions, showing that PGD is more efficient in selecting embryos that will reach term.