SCORING CRITERIA FOR PREIMPLANTATION GENETIC DIAGNOSIS OF NUMERICAL ABNORMALITIES FOR CHROMOSOME-X, CHROMOSOME-Y, CHROMOSOME-13, CHROMOSOME-16, CHROMOSOME-18 AND CHROMOSOME-21

Fluorescence in-situ hybridization (FISH) for application in preimplan tation genetic diagnosis (PGD) of aneuploidy has been used successfull y, but stringent scoring criteria to score FISH signals have not been developed. In the present study a FISH protocol to simultaneously enum erate chromosomes X, Y, 13, 16, 18, and 21 was used to evaluate two di fferent scoring criteria. The criteria consider hybridization signal s ize, shape, and vicinity to other signals and nuclear diameter. For th is purpose, 74 embryos (412 blastomeres) donated for research had most or all of their cells analysed. The least error-prone criterion (9%) was selected for use in PGD cases. Some probes produced more errors th an others, and these criteria may provide clues to improve these probe s. The same probe solution was applied to 55 PGD cases and a total of 307 embryos. Of the non-transferred embryos, 67 were fully reanalysed and 1.5% (1/67) of them were falsely diagnosed as normal, while 19% (1 3/67) were falsely diagnosed as abnormal. Twelve of the patients becam e pregnant after PGD.