P-242 Genetic laboratories report significantly different aneuploidy rates for identical patient populations, a finding with important implications for clinics using PGT-A

Abstract Study question If a clinic changes the genetic laboratory it works with, should expect its new PGT-A results to be equivalent those received previously? Summary answer Changing service provider can result in significant difference proportion of embryos classified euploid, with important clinical implications. What is known already Preimplantation testing for aneuploidy (PGT-A) aims distinguish potentially viable euploid from harbouring lethal chromosome abnormalities. Typically, IVF clinics perform biopsy at blastocyst stage and send resulting trophectoderm specimens specialist laboratories analysis. However, many commercially available methods have not been subjected rigorous validation, leading uncertainty about their accuracy predictive value. It would concerning if classification embryos, derived same patient population, clinic, varied depending on company that provides services. Such differences unlikely reflect biological reality. design, size, duration Our recently began working genetics company. previous reference issued 1,136 over ∼15 months. Subsequently, second tested 784 samples 7 Patient populations during two periods were essentially identical (average maternal age 38.0 years). Participants/materials, setting, The first used whole genome amplification followed by next generation sequencing (NGS) evaluate relative amount DNA each chromosome. company’s method was highly validated, involving targeted thousands sites genome, again NGS analysis quantity individual chromosomes. Additionally, they genotyped numerous polymorphisms, which assist detection haploidy/triploidy, also reveals problems compromise (e.g. contamination). Main role chance 44.4% blastocysts 4.1% low-level mosaic, 51.5% aneuploid. In contrast, reported significantly fewer aneuploid (44.0%; P = 0.0019). Even mosaics are considered transfer, still associated more transferable (relative increase greater than one-sixth). correct, implies may misclassified company, risking exclusion loss pregnancies might produced. Conversely, failing detect some aneuploidies, inadvertent transfer abnormal lower pregnancy rates higher incidence miscarriage. 299 transfers following using produced 171 (74.7%), while 64 single embryo taken place after 53 (82.8% per transfer). Losses (biochemical or miscarriage) affected 21.6% 16.9% conducted companies, respectively (ongoing 58.5% 68.8% respectively) Thus, there no evidence aneuploidies being missed Limitations, reasons caution Although obvious between patients this study prospective nor randomized, so possibility undetected remains. sufficiently powered test significance apparent implantation, miscarriage ongoing rates. Wider implications findings appreciate differ significantly, undergone much validation others. recommended ask PGT providers share data, especially studies confirming ‘aneuploid’ ‘abnormal’ truly non-viable. Trial registration number Not applicable