Cytogenomic results following high-chance non-invasive prenatal testing: a UK national audit

Fiona S. Togneri,Kathy Mann,Stephanie K. Allen,Sian Morgan,Elaine Holgado

doi:10.1017/s0016672320000087

Fiona S. Togneri, Kathy Mann

Open Access

https://doi.org/10.1017/s0016672320000087

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Abstract

Non-invasive prenatal testing (NIPT) is increasingly being adopted as a screening test in the UK and is currently accessed through certain National Health Service healthcare systems or by private provision. This audit aims to describe reasons for and results of cytogenomic investigations carried out within UK genetic laboratories following an NIPT result indicating increased chance of cytogenomic abnormality ('high-chance NIPT result'). A questionnaire was sent out to 24 genetics laboratories in the UK and completed by 18/24 (75%). Data were returned representing 1831 singleton pregnancies. A total of 1329 (73%) invasive samples were taken following NIPT results showing a high chance of trisomy 21; this was confirmed in 1305 (98%) of these by invasive sampling. Trisomy 21 was confirmed in >99% of patients who also had high-screen risk results or abnormal scan findings. Amongst invasive samples taken due to NIPT results indicating a high chance of trisomy 18, 84% yielded a compatible result, and this number dropped to 49% for trisomy 13 and 51% for sex chromosomes. In the UK, the majority of patients having invasive sampling for high-chance NIPT results are doing so following an NIPT result indicating an increased chance of common trisomies (92%). In this population, NIPT performs particularly well for trisomy 21, but less well for other indications.

Highlights

Since its introduction, non-invasive prenatal testing (NIPT) has been enthusiastically adopted as a prenatal screen across the globe (Minear et al, 2015)
Data were provided for a total of 1831 invasive samples from singleton pregnancies (1083 amniotic fluid samples and 748 chorionic villus samples), all taken following NIPT results indicating a high chance of genomic imbalance or following failed NIPT studies
Reason for NIPT was stipulated for nine of these pregnancies; three pregnancies had abnormal scan findings and six had an increased screen risk from combined first-trimester screening. This is the first UK-wide study describing the population of patients requesting invasive prenatal genetic diagnosis within the UK healthcare system following NIPT results that indicate a high chance of genomic imbalance or an inconclusive result

Summary

Introduction

Non-invasive prenatal testing (NIPT) has been enthusiastically adopted as a prenatal screen across the globe (Minear et al, 2015). Access to NIPT across the rest of the UK is currently inconsistent. Some NHS Trusts are offering local services (Wald et al, 2018; Togneri et al, 2019; Sacco et al, 2020), but much NIPT is being obtained on a private basis. All NIPT providers test for trisomy 13, 18 and 21; only a proportion test for sex chromosome aneuploidy, other autosomal aneuploidies and structural chromosome abnormalities such as microdeletion syndromes. Despite much NIPT being obtained on a private basis, patients who receive a high-chance result usually access genetic counselling and follow-up invasive procedures through NHS healthcare services. Invasive samples (amniocentesis or chorionic villus samples) taken for genetic diagnosis are sent to 1 of 24 mainly NHS-based UK genetics laboratories for analysis

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