EXAMINATION OF INTER CENTRE VARIATION IN PGT-A "NO RESULT RATE" AND EFFICACY OF REBIOPSY - ANALYSIS OF 22,833 SAMPLES 2015-2019

Abstract

To investigate variation in PGT-A "no result" rates between referring clinics, investigate the fate of "no result" embryos, and compare clinical outcomes of "no result" embryo transfer versus rebiopsied embryos. A retrospective analysis was performed of trophectoderm samples submitted for PGT-A via NGS over a 5yr period, 2015-2019. Data was collected on 22833 trophectoderm samples, submitted by 30 IVF laboratories. The no result (NR) rate was calculated per year and per clinic. Clinics were contacted for follow up data on NR embryos in terms of usage and clinical outcomes. Clinics were asked if embryos selected for transfer had survived (re)warming, and to provide clinical follow-up including hCG test, clinical pregnancies, miscarriage and livebirth. Clinical outcomes from rebiopsied embryos were compared with those transferred as NR without rebiopsy. The two tailed Fishers exact test was used for statistical analysis. There was a wide range in sample numbers submitted by clinics over the time period, ranging from 9 samples through to 2633. In clinics submitting over 500 samples the NR rate ranged from 0.6% to 7.4%, and in the those submitting 100-499 samples it ranged from 1.1% to 5.8%. Both these differences proved to be statistically significant (p<0.05). Less than 50% of NR embryos underwent rebiopsy. While the majority of embryos undergoing rebiopsy yielded a result (92.3%) and 31.4% of these were euploid or mosaic, almost half still remain in storage. The rate of livebirth/ongoing implantation in the rebiopsy group is 35.5% and 17.1% in the non rebiopsy group, illustrating a non significant trend towards a higher chance of implantation and livebirth in the rebiopsy group. Of 58 patients undergoing rebiopsy without any euploids in their initial cycle, 18 had a euploid embryo identified for future use. Despite starting with 22833 samples, 1115 of which were classified as NR, there were only 31 rebiopsied and 42 NR embryos transferred. In line with existing literature, data suggests rebiopsy reduces livebirth rates compared to standard PGT-A cycles. However, this study indicates clinical outcomes are better in the rebiopsy transfer group versus the NR transfer group. There is the potential for more data to be generated from embryos still in storage, and so clinical outcome data must continue to be collected to evidence clear benefit to the patient of the rebiopsy procedure.