Accuracy of FISH analysis in predicting chromosomal status in patients undergoing preimplantation genetic diagnosis

Objective: The purpose of this Study was to determine the positive predictive value (PPV) and negative predictive value (NPV) of FISH analysis and to determine which chromosomal abnormalities are most frequently confirmed. Design: Prospective observational. Setting: IVF laboratory. Patient(s): Two hundred forty-one embryos were analyzed from 98 patients. Intervention(s): FISH reanalysis. Main Outcome Measure(s): Embryos that would have been discarded in patients undergoing preimplantation genetic diagnosis (PGD) were fixed and FISH reanalysis was performed. Results of reanalysis were compared with the day 3 diagnosis while PPV and NPV were calculated. Result(s): Among the 241 embryos, 198 embryos were abnormal and 43 were normal by day 3 FISH analysis. The PPV was 83% and the NPV was 81%. PPV was also determined for specific categories of aneuploidy, and certain abnormalities such as monosomies, trisomies, tetrasomies, and polyploidies were frequently confirmed on reanalysis (PPV >80%), whereas Turner syndrome diagnosis was not (PPV = 17%). Conclusion(s): FISH analysis offers a PPV of 83% and NPV of 81% when evaluating a single blastomere in conjunction with PGD. FISH errors and mosaicism are primarily responsible for the errors associated with FISH analysis in PGD.