Combined aneuploidy and translocation testing in polar bodies
Introduction: Diagnosis in aborted material of translocation carriers often detects aneuploidies, together with a balanced karyotype for the translocation. There is still an ongoing contraversiary discussion if there is a higher rate of aneuploidies in translocation carriers. The aim of our study is to detect both, imbalances and aneuploidies in oocytes, by polar body diagnosis.
Methods: After oocyte retreival, first polar bodies were extracted after their zona pellucida had been opened by diode laser or acid Tyrode´s solution. After fixing on slides the polar bodies underwent two rounds of fluorescence in situ hybridisation (FISH), one for detection of the chromosome fragments involved in the translocation, and the other for recognition of aneuploidies for the chromosomes 13, 16, 18, 21 and 22 (MultiVysion PB, Abbott).
Results: Both rounds of FISH could subsequently be performed within 4 h and 12 h. All polar bodies were reidentified after rehybridisation. Within twenty hours after intracytoplasmic sperm injection, results of both FISH rounds could be obtained. It could be shown that only a third of the oocytes were balanced referring to the distinct analysed translocation, furthermore one third of these balanced oocytes were aneuploid. Thus, only every fifth analysed oocyte were shown to be both, balanced and euploid for the tested chromosomes, and could subsequently be cultivated for future embryo transfer.
Conclusions: Testing of both, chromosomal imbalances of translocations and aneuploidies, reveal a more reliable result in preimplantation diagnosis of translocation carriers. Consequently, at least 10 matured oocytes per patient are a prerequisite for finally culture and transfer of one or two embryos.