Improving the fixation method for preimplantation genetic diagnosis by fluorescent in situ hybridization

Purpose: Our purpose was to modify, a fixation method using Tween-20 and HCl (TH) and to compare it with a protocol using methanol and acetic acid (MA) for the improvement of preimplantation genetic diagnosis by fluorescence in situ hybridization (FISH). Methods: Single blastomeres were allocated to either the TH or the MA procedure. The two methods were compared to evaluate efficiency of fixation and the intensities of FISH signals, Results: With the TH method, 123 (93.9%) of 131 blastomeres were fixed, while only 95 (78.5%) of 121 were fixed with MA. Average scores far the intensity of FISH signals were significantly stronger for TH than for MA (P < 0.05). There was also a significant difference in signal intensity scores between the two methods for type-3 nuclei. Conclusions: Our results indicate that not only are fewer nuclei last during fixation but also stronger FISH signals can be obtained with the TH method. Thus, modified TH can improve the overall efficiency of preimplantation genetic diagnosis.