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Plain language summary: Structural differences (congenital anomalies) in the makeup of the baby's heart, brain and other organs are found on antenatal ultrasound scans in up to 3% of pregnancies. These often have a genetic cause, arising because of changes in the chromosomes (which store our genetic material) or the DNA code that make up the genes. The more differences a baby has the more likely the risk of underlying genetic disease. If a structural difference is found, parents are usually offered a genetic test, which may be carried out on cells taken either from the placenta (chorionic villous sampling) or the fluid surrounding the baby (amniocentesis). At the moment, these cells are only tested for changes in the chromosomes and are only able to reveal the underlying cause in about 40% of unborn babies. Prenatal exome sequencing (ES) is a new genetic test, which, when combined with testing the DNA of both parents can find changes in the baby's genetic code. If a DNA change is found that can explain the structural changes seen on ultrasound, specific information about the underlying diagnosis can be given to the parents. Having this information can help parents make important decisions about their ongoing pregnancy, as well as help doctors to care for the mother and baby. Finding a genetic change can also help to understand how the condition has arisen and whether it might happen again in another pregnancy. It may also be possible to test for the genetic condition in future pregnancies. Although prenatal ES is an exciting new way to improve diagnosis rates for structural differences, it has some challenges. While the test is very detailed, it may not always find a genetic explanation and sometimes the results are difficult to interpret. For example, genetic changes can be found where their significance for the pregnancy is unclear. More recently, two studies have now shown that prenatal ES can find a genetic diagnosis in at least 10% of pregnancies with structural differences where standard chromosome testing has been negative. This paper reviews these studies, along with earlier evidence on ES and provides clinicians with guidance for future practice. [ABSTRACT FROM AUTHOR]

Objective To assess the views and likely uptake of non-invasive prenatal testing ( NIPT) for trisomy 21 among potential service users in the UK. Design Cross-sectional survey. Setting Four antenatal clinics in England and two websites. Sample A total of 1131 women and partners. Methods Questionnaire conducted with women (and partners) recruited through antenatal clinics, a random sample of members of the website Mumsnet, and viewers of the website and Facebook page of the support group Antenatal Results and Choices ( ARC). Main outcome measures Factors impacting decision-making towards prenatal testing; views on NIPT, including service delivery and likely uptake; hypothetical scenarios, focused on current screening, invasive testing, and NIPT offered to women with a high-risk screening result. Results The vast majority (95.7%; 1071/1119; 95% CI 94.4-96.8%) thought NIPT was a positive development in prenatal care, with 88.2% (972/1103; 95% CI 86.1-90%) indicating that they would use the test, including respondents who would currently decline trisomy 21 screening ( P < 0.001). Of the respondents who would have NIPT, 30.7% (299/973; 95% CI = 27.8-33.7%) said that they were 'likely' to terminate an affected pregnancy (including those who would currently decline screening or invasive testing), and 36.5% (355/973; 95% CI 33.5-39.6%) were 'not likely' to terminate an affected pregnancy. Respondents overwhelmingly indicated that safety for the baby was the most important attribute of NIPT (70.1%; 712/1015; 95% CI 67.2-73%). Conclusion Respondents were overwhelmingly positive towards the introduction of NIPT. Uptake is likely to be high, and includes women who currently decline screening as well as those who will use the test for information only. Pre-test counselling to ensure that women understand the implications of the test result is essential. [ABSTRACT FROM AUTHOR]

Objective: Perinatal autopsy provides additional diagnostic information in a significant proportion of cases but parents and relatives frequently decline traditional postmortem (PM) examination, partly due to the unacceptability of the cosmetic effects of large incisions and concerns regarding organ retention. We present a novel minimally invasive autopsy method for fetal and neonatal PMexaminations, which includes PM magnetic resonance imaging (MRI) for assessment of anatomy and endoscopic internal examination to allow direct organ visualization and targeted tissue biopsy.Methods: Descriptive retrospective feasibility report of the first 10 perinatal cases undergoing endoscopic minimally invasive autopsy.Results: A minimally invasive autopsy (MIA) approach based on postmortem MRI (PM MRI) and endoscopic autopsy with tissue biopsy is feasible and effective with minimal cosmetic consequences compared to traditional PM examination. Endoscopic examination with tissue biopsy provided additional diagnostic information to PM MRI alone in the majority of cases.Conclusions: Endoscopic MIA is a feasible and potentially more acceptable approach to perinatal autopsy and provides an additional option for parents who do not agree to a traditional PM examination. This approach could result in increased utilization of investigations after death in this group of patients. [ABSTRACT FROM AUTHOR]

Folic acid supplementation can prevent many cases of neural tube defects (NTDs), whereas suboptimal maternal folate status is a risk factor, suggesting that folate metabolism is a key determinant of susceptibility to NTDs. Despite extensive genetic analysis of folate cycle enzymes, and quantification of metabolites in maternal blood, neither the protective mechanism nor the relationship between maternal folate status and susceptibility are understood in most cases. In order to investigate potential abnormalities in folate metabolism in the embryo itself, we derived primary fibroblastic cell lines from foetuses affected by NTDs and subjected them to the dU suppression test, a sensitive metabolic test of folate metabolism. Significantly, a subset of NTD cases exhibited low scores in this test, indicative of abnormalities in folate cycling that may be causally linked to the defect. Susceptibility to NTDs may be increased by suppression of the methylation cycle, which is interlinked with the folate cycle. However, reduced efficacy in the dU suppression test was not associated with altered abundance of the methylation cycle intermediates, s-adenosylmethionine and s-adenosylhomocysteine, suggesting that a methylation cycle defect is unlikely to be responsible for the observed abnormality of folate metabolism. Genotyping of samples for known polymorphisms in genes encoding folate-associated enzymes did not reveal any correlation between specific genotypes and the observed abnormalities in folate metabolism. These data suggest that as yet unrecognized genetic variants result in embryonic abnormalities of folate cycling that may be causally related to NTDs. [ABSTRACT FROM AUTHOR]

Prenatal sequencing tests are being introduced into clinical practice in many developed countries. In part due to its greater ability to detect genetic variation, offering prenatal sequencing can present ethical challenges. Here we review ethical issues arising following the implementation of prenatal sequencing in the English National Health Service (NHS). We analysed semi structured interviews conducted with 48 parents offered prenatal sequencing and 63 health professionals involved in delivering the service to identify the ethical issues raised. Two main themes were identified: (1) Equity of access (including issues around eligibility criteria, laboratory analytical processes, awareness and education of clinicians, fear of litigation, geography, parental travel costs, and access to private healthcare), and (2) Timeliness and its impact on parental decision-making in pregnancy (in the context of the law around termination of pregnancy, decision-making in the absence of prenatal sequencing results, and the "importance" of prenatal sequencing results). Recognising both the practical and systemic ethical issues that arise out of delivering a national prenatal sequencing service is crucial. Although specific to the English context, many of the issues we identified are applicable to prenatal sequencing services more broadly. Education of health professionals and parents will help to mitigate some of these ethical issues., (© 2024. The Author(s).)

Background: Evidence suggests that coordination of care for people affected by rare diseases is poor. In order to improve the way that care is coordinated it is necessary to understand the preferences of people affected by these conditions, and providers. The aim of this study was to examine patient, parent and carer, and health care professional preferences for different attributes of care coordination for people affected by rare diseases. We conducted a discrete choice experiment using online surveys. There were no restrictions on participants in terms of rare conditions, demographic factors other than age, or geographical location within the UK. Choice scenarios were based on the following attributes: annual cost of attending appointments; access to health records; access to clinical expertise; support of a care coordinator; access to a specialist centre; and, the existence of a documented plan for emergency care. Data were analysed using alternative-specific conditional logit regression models., Results: Valid responses were obtained from 996 individuals (528 patients, 280 carers, 188 health care professionals) between August and December 2019. All attributes significantly influenced the type of service respondents preferred. Patients, carers and health professionals' preferences for care coordination were influenced by: the cost of attending appointments; access to health records; clinical expertise; role of care coordinators; access to specialist centres; and the existence of plan for emergency care. There were no statistically significant differences in the preferences between patients and carers. Preferences of health professionals differed to those of patients and carers. Both patients and carers selected responses which granted them a greater degree of autonomy in relation to the role of care coordinators, whereas health professionals preferred services where care coordinators had more autonomy. Health care professionals also expressed a stronger preference for a documented formal emergency plan to be in place., Conclusions: The findings highlight that people value better coordinated care, in line with policy documents emphasising commitments to coordinated care for people affected by rare diseases. This study highlights the factors that could be included in service provision as ways of improving the coordination of care for people affected by rare diseases., (© 2024. The Author(s).)

Clinical whole-genome sequencing (WGS) has been shown to deliver potential benefits to children with cancer and to alter treatment in high-risk patient groups. It remains unknown whether offering WGS to every child with suspected cancer can change patient management. We collected WGS variant calls and clinical and diagnostic information from 281 children (282 tumors) across two English units (n = 152 from a hematology center, n = 130 from a solid tumor center) where WGS had become a routine test. Our key finding was that variants uniquely attributable to WGS changed the management in ~7% (20 out of 282) of cases while providing additional disease-relevant findings, beyond standard-of-care molecular tests, in 108 instances for 83 (29%) cases. Furthermore, WGS faithfully reproduced every standard-of-care molecular test (n = 738) and revealed several previously unknown genomic features of childhood tumors. We show that WGS can be delivered as part of routine clinical care to children with suspected cancer and can change clinical management by delivering unexpected genomic insights. Our experience portrays WGS as a clinically impactful assay for routine practice, providing opportunities for assay consolidation and for delivery of molecularly informed patient care., (© 2024. The Author(s).)

Introduction: In October 2020, rapid prenatal exome sequencing (pES) was introduced into routine National Health Service (NHS) care in England, requiring the coordination of care from specialist genetics, fetal medicine (FM) and laboratory services. This mixed methods study explored the experiences of professionals involved in delivering the pES service during the first 2 years of its delivery in the NHS., Methods: A survey ( n = 159) and semi-structured interviews ( n = 63) with healthcare professionals, including clinical geneticists, FM specialists, and clinical scientists (interviews only) were used to address: 1) Views on the pES service; 2) Capacity and resources involved in offering pES; 3) Awareness, knowledge, and educational needs; and 4) Ambitions and goals for the future., Results: Overall, professionals were positive about the pES service with 77% rating it as Good or Excellent. A number of benefits were reported, including the increased opportunity for receiving actionable results for parental decision-making, improving equity of access to genomic tests and fostering close relationships between FM and genetics departments. Nonetheless, there was evidence that the shift to offering pES in a clinical setting had brought some challenges, such as additional clinic time, administrative processes, perceived lack of autonomy in decision-making regarding pES eligibility and difficulty engaging with peripheral maternity units. Concerns were also raised about the lack of confidence and gaps in genomics knowledge amongst non-genetics professionals - especially midwives. However, the findings also highlighted value in both FM, obstetric and genetics professionals benefiting from further training with a focus on recognising and managing prenatally diagnosed genetic conditions., Conclusion: Healthcare professionals are enthusiastic about the benefits of pES, and through multi-collaborative working, have developed relationships that have contributed to effective communication across specialisms. Although limitations on resources and variation in knowledge about pES have impacted service delivery, professionals were hopeful that improvements to infrastructure and the upskilling of all professionals involved in the pathway would optimise the benefits of pES for both parents and professionals., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Peter, Mellis, McInnes-Dean, Daniel, Walton, Fisher, Leeson-Beevers, Allen, Baple, Beleza-Meireles, Bertoli, Campbell, Canham, Cilliers, Cobben, Eason, Harrison, Holder-Espinasse, Male, Mansour, McEwan, Park, Smith, Stewart, Tapon, Vasudevan, Williams, Wu, Chitty and Hill.)

Introduction: Severe osteogenesis imperfecta (OI) is a debilitating disease with no cure or sufficiently effective treatment. Mesenchymal stem cells (MSCs) have good safety profile, show promising effects and can form bone. The Boost Brittle Bones Before Birth (BOOSTB4) trial evaluates administration of allogeneic expanded human first trimester fetal liver MSCs (BOOST cells) for OI type 3 or severe type 4., Methods and Analysis: BOOSTB4 is an exploratory, open-label, multiple dose, phase I/II clinical trial evaluating safety and efficacy of postnatal (n=15) or prenatal and postnatal (n=3, originally n=15) administration of BOOST cells for the treatment of severe OI compared with a combination of historical (1-5/subject) and untreated prospective controls (≤30). Infants<18 months of age (originally<12 months) and singleton pregnant women whose fetus has severe OI with confirmed glycine substitution in COL1A1 or COL1A2 can be included in the trial.Each subject receives four intravenous doses of 3×10 6 /kg BOOST cells at 4 month intervals, with 48 (doses 1-2) or 24 (doses 3-4) hours in-patient follow-up, primary follow-up at 6 and 12 months after the last dose and long-term follow-up yearly until 10 years after the first dose. Prenatal subjects receive the first dose via ultrasound-guided injection into the umbilical vein within the fetal liver (16+0 to 35+6 weeks), and three doses postnatally.The primary outcome measures are safety and tolerability of repeated BOOST cell administration. The secondary outcome measures are number of fractures from baseline to primary and long-term follow-up, growth, change in bone mineral density, clinical OI status and biochemical bone turnover., Ethics and Dissemination: The trial is approved by Competent Authorities in Sweden, the UK and the Netherlands (postnatal only). Results from the trial will be disseminated via CTIS, ClinicalTrials.gov and in scientific open-access scientific journals., Trial Registration Numbers: EudraCT 2015-003699-60, EUCT: 2023-504593-38-00, NCT03706482., Competing Interests: Competing interests: ALD is a consultant for Esperare Foundation for a clinical trial unrelated to this work. CG, LW-J and MW are cofounders and coowners of BOOST Pharma ApS founded in 2020. OS is a scientific advisor for BOOST Pharma ApS., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.)

Objectives: To determine the incremental yield of prenatal exome sequencing (PES) over standard testing in fetuses with an isolated congenital heart abnormality (CHA), CHA associated with extra-cardiac malformations (ECMs) and CHA dependent upon anatomical subclassification., Methods: A systematic review of the literature was performed using MEDLINE, EMBASE, Web of Science and grey literature January 2010-February 2023. Studies were selected if they included greater than 20 cases of prenatally diagnosed CHA when standard testing (QF-PCR/chromosome microarray/karyotype) was negative. Pooled incremental yield was determined. PROSPERO CRD 42022364747., Results: Overall, 21 studies, incorporating 1957 cases were included. The incremental yield of PES (causative pathogenic and likely pathogenic variants) over standard testing was 17.4% (95% CI, 13.5%-21.6%), 9.3% (95% CI, 6.6%-12.3%) and 35.9% (95% CI, 21.0%-52.3%) for all CHAs, isolated CHAs and CHAs associated with ECMs. The subgroup with the greatest yield was complex lesions/heterotaxy; 35.2% (95% CI 9.7%-65.3%). The most common syndrome was Kabuki syndrome (31/256, 12.1%) and most pathogenic variants occurred de novo and in autosomal dominant (monoallelic) disease causing genes (114/224, 50.9%)., Conclusion: The likelihood of a monogenic aetiology in fetuses with multi-system CHAs is high. Clinicians must consider the clinical utility of offering PES in selected isolated cardiac lesions., (© 2024 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd.)

Background: Cell-free fetal DNA exists within the maternal bloodstream during pregnancy and provides a means for noninvasive prenatal diagnosis (NIPD). Our accredited clinical service offers definitive NIPD for several autosomal recessive (AR) and X-linked conditions using relative haplotype dosage analysis (RHDO). RHDO involves next-generation sequencing (NGS) of thousands of common single nucleotide polymorphism (SNPs) surrounding the gene of interest in the parents and an affected or unaffected offspring to conduct haplotype phasing of the high- and low-risk alleles. NGS is carried out in parallel on the maternal cell-free DNA, and fetal inheritance is predicted using sensitive dosage calculations performed at sites where the parental genotypes differ. RHDO is not currently offered to consanguineous couples owing to the shared haplotype between parents. Here we test the expansion of RHDO for AR monogenic conditions to include consanguineous couples., Methods: The existing sequential probability ratio test analysis pipeline was modified to apply to SNPs where both parents are heterozygous for the same genotype. Quality control thresholds were developed using 33 nonconsanguineous cases. The performance of the adapted RHDO pipeline was tested on 8 consanguineous cases., Results: The correct fetal genotype was predicted by our revised RHDO approach in all conclusive cases with known genotypes (n = 5). Haplotype block classification accuracies of 94.5% and 93.9% were obtained for the nonconsanguineous and consanguineous case cohorts, respectively., Conclusions: Our modified RHDO pipeline correctly predicts the genotype in fetuses from consanguineous families, allowing the potential to expand access to NIPD services for these families., (© Association for Diagnostics & Laboratory Medicine 2024.)

Noninvasive cfDNA testing for monogenic disorders (sgNIPT) has become integrated into the care of pregnant women at increased risk based on carrier status, known family history, or ultrasound anomalies. The availability of commercial tests for common autosomal recessive and de novo autosomal dominant conditions has led to the use of these tests in low-risk pregnancies. However, is the technology ready for use in this low-risk population? This report is a summary of the debate on this topic at the 27 th International Conference on Prenatal Diagnosis and Therapy. Both expert debaters provided strong arguments in favor and against the use of sgNIPT in low-risk pregnancies. The argument in favor of sgNIPT for autosomal recessive conditions is that it allows the identification of affected pregnancies without the need for involving the partner in testing. Arguments for sgNIPT for autosomal dominant conditions include identification of affected fetuses that would have either presented later in pregnancy with fetal anomalies or not been detected prenatally given normal ultrasounds, respect for patient autonomy and patient desire for information. Strong arguments were made against offering sgNIPT screening. Given that traditional carrier screening for recessive conditions can be carried out in many jurisdictions, the added value of sgNIPT has not been clearly demonstrated. Arguments against sgNIPT for autosomal dominant conditions included the total lack of clinical validation studies and the risk of false reassurance in cases of negative results and unnecessary invasive procedures in cases of false positive results. Although there is a desire to take advantage of new technologies to improve the detection of monogenic disorders in low-risk populations, based on the discussion and the audience vote, it appears premature to offer sgNIPT to all low risk pregnant women. Further clinical validation studies are needed prior to broad implementation., (© 2023 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd.)

Objectives: Determine the incremental diagnostic yield of prenatal exome sequencing (pES) over chromosome microarray (CMA) or G-banding karyotype in fetuses with central nervous system (CNS) abnormalities., Methods: Data were collected via electronic searches from January 2010 to April 2022 in MEDLINE, Cochrane, Web of Science and EMBASE. The NHS England prenatal exome cohort was also included. Incremental yield was calculated as a pooled value using a random-effects model., Results: Thirty studies were included (n = 1583 cases). The incremental yield with pES for any CNS anomaly was 32% [95%CI 27%-36%; I 2  = 72%]. Subgroup analysis revealed apparent incremental yields in; (a) isolated CNS anomalies; 27% [95%CI 19%-34%; I 2  = 74%]; (b) single CNS anomaly; 16% [95% CI 10%-23%; I 2  = 41%]; (c) more than one CNS anomaly; 31% [95% Cl 21%-40%; I 2  = 56%]; and (d) the anatomical subtype with the most optimal yield was Type 1 malformation of cortical development, related to abnormal cell proliferation or apoptosis, incorporating microcephalies, megalencephalies and dysplasia; 40% (22%-57%; I 2  = 68%). The commonest syndromes in isolated cases were Lissencephaly 3 and X-linked hydrocephalus., Conclusions: Prenatal exome sequencing provides a high incremental diagnostic yield in fetuses with CNS abnormalities with optimal yields in cases with multiple CNS anomalies, particularly those affecting the midline, posterior fossa and cortex., (© 2023 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd.)

Objectives: In October 2020, rapid prenatal exome sequencing (pES) was introduced into routine National Health Service (NHS) care in England. This study aimed to explore parent experiences and their information and support needs from the perspective of parents offered pES and of health professionals involved in its delivery., Methods: In this qualitative study, semi-structured interviews were conducted with 42 women and 6 male partners and 63 fetal medicine and genetic health professionals. Interviews were transcribed verbatim and analysed using thematic analysis., Results: Overall views about pES were positive and parents were grateful to be offered the test. Highlighted benefits of pES included the value of the additional information for pregnancy management and planning for future pregnancies. An anxious wait for results was common, often associated with the need to make decisions near to 24 weeks in pregnancy when there are legal restrictions for late termination. Descriptions of dealing with uncertainty were also common, even when results had been returned. Many parents described pES results as informing decision-making around whether or not to terminate pregnancy. Some professionals were concerned that a non-informative result could be overly reassuring and highlighted that careful counselling was needed to ensure parents have a good understanding of what the result means for their pregnancy. Emotional support from professionals was valued; however, some parents felt that post-test support was lacking., Conclusion: Parents and professionals welcomed the introduction of pES. Results inform parents' decision-making around the termination of pregnancy. When there are no diagnostic findings or uncertain findings from pES, personalised counselling that considers scans and other tests are crucial. Directing parents to reliable online sources of information and providing emotional support throughout could improve their experiences of care., (© 2024 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd.)

We used cross-sectional surveys to compare the knowledge, attitudes, and decision regret of participants who had consented for genome sequencing (GS) for rare disease diagnosis in the 100,000 Genomes Project (100kGP) across two timepoints (at the time of consenting for GS (T1) and 12-18 months later (T2)). At T1, participants (n = 504) completed a survey that included measures of general knowledge of GS ("Knowledge of Genome Sequencing" (KOGS)), specific knowledge of GS and attitudes towards GS ("General attitudes" and "Specific attitudes"). At T2, participants (n = 296) completed these same assessments (apart from the specific knowledge scale) together with an assessment of decision regret towards GS ("Decisional Regret Scale"). At 12-18 months after consenting for GS, participants' basic knowledge of GS had remained stable. General knowledge of GS varied across topics; concepts underlying more general information about genetics were better understood than the technical details of genomic testing. Attitudes towards GS at T2 were generally positive, and feelings towards GS (both positive and negative) remained unchanged. However, those who were more positive about the test at the outset had greater specific knowledge (as opposed to general knowledge) of GS. Finally, although the majority of participants indicated feeling little regret towards undergoing GS, those with low positive attitude and high negative attitude about GS at T1 reported greater decision regret at T2. Careful assessment of patient knowledge about and attitudes towards GS at the time of offering testing is crucial for supporting informed decision making and mitigating later regret., (© 2023. The Author(s).)

Background: Poorly coordinated care can have major impacts on patients and families affected by rare conditions, with negative physical health, psychosocial and financial consequences. This study aimed to understand how care is coordinated for rare diseases in the United Kingdom., Methods: We undertook a national survey in the UK involving 760 adults affected by rare diseases, 446 parents/carers of people affected by rare diseases, and 251 healthcare professionals who care for people affected by rare diseases., Results: Findings suggested that a wide range of patients, parents and carers do not have coordinated care. For example, few participants reported having a care coordinator (12% patients, 14% parents/carers), attending a specialist centre (32% patients, 33% parents/carers) or having a care plan (10% patients, 44% parents/carers). A very small number of patients (2%) and parents/carers (5%) had access to all three-a care coordinator, specialist centre and care plan. Fifty four percent of patients and 33% of parents/carers reported access to none of these. On the other hand, a higher proportion of healthcare professionals reported that families with rare conditions had access to care coordinators (35%), specialist centres (60%) and care plans (40%)., Conclusions: Care for families with rare conditions is generally not well coordinated in the UK, with findings indicating limited access to care coordinators, specialist centres and care plans. Better understanding of these issues can inform how care coordination might be improved and embrace the needs and preferences of patients and families affected by rare conditions., (© 2023. The Author(s).)

Background: Most neonatal and infantile-onset epilepsies have presumed genetic aetiologies, and early genetic diagnoses have the potential to inform clinical management and improve outcomes. We therefore aimed to determine the feasibility, diagnostic yield, and clinical utility of rapid genome sequencing in this population., Methods: We conducted an international, multicentre, cohort study (Gene-STEPS), which is a pilot study of the International Precision Child Health Partnership (IPCHiP). IPCHiP is a consortium of four paediatric centres with tertiary-level subspecialty services in Australia, Canada, the UK, and the USA. We recruited infants with new-onset epilepsy or complex febrile seizures from IPCHiP centres, who were younger than 12 months at seizure onset. We excluded infants with simple febrile seizures, acute provoked seizures, known acquired cause, or known genetic cause. Blood samples were collected from probands and available biological parents. Clinical data were collected from medical records, treating clinicians, and parents. Trio genome sequencing was done when both parents were available, and duo or singleton genome sequencing was done when one or neither parent was available. Site-specific protocols were used for DNA extraction and library preparation. Rapid genome sequencing and analysis was done at clinically accredited laboratories, and results were returned to families. We analysed summary statistics for cohort demographic and clinical characteristics and the timing, diagnostic yield, and clinical impact of rapid genome sequencing., Findings: Between Sept 1, 2021, and Aug 31, 2022, we enrolled 100 infants with new-onset epilepsy, of whom 41 (41%) were girls and 59 (59%) were boys. Median age of seizure onset was 128 days (IQR 46-192). For 43 (43% [binomial distribution 95% CI 33-53]) of 100 infants, we identified genetic diagnoses, with a median time from seizure onset to rapid genome sequencing result of 37 days (IQR 25-59). Genetic diagnosis was associated with neonatal seizure onset versus infantile seizure onset (14 [74%] of 19 vs 29 [36%] of 81; p=0·0027), referral setting (12 [71%] of 17 for intensive care, 19 [44%] of 43 non-intensive care inpatient, and 12 [28%] of 40 outpatient; p=0·0178), and epilepsy syndrome (13 [87%] of 15 for self-limited epilepsies, 18 [35%] of 51 for developmental and epileptic encephalopathies, 12 [35%] of 34 for other syndromes; p=0·001). Rapid genome sequencing revealed genetic heterogeneity, with 34 unique genes or genomic regions implicated. Genetic diagnoses had immediate clinical utility, informing treatment (24 [56%] of 43), additional evaluation (28 [65%]), prognosis (37 [86%]), and recurrence risk counselling (all cases)., Interpretation: Our findings support the feasibility of implementation of rapid genome sequencing in the clinical care of infants with new-onset epilepsy. Longitudinal follow-up is needed to further assess the role of rapid genetic diagnosis in improving clinical, quality-of-life, and economic outcomes., Funding: American Academy of Pediatrics, Boston Children's Hospital Children's Rare Disease Cohorts Initiative, Canadian Institutes of Health Research, Epilepsy Canada, Feiga Bresver Academic Foundation, Great Ormond Street Hospital Charity, Medical Research Council, Murdoch Children's Research Institute, National Institute of Child Health and Human Development, National Institute for Health and Care Research Great Ormond Street Hospital Biomedical Research Centre, One8 Foundation, Ontario Brain Institute, Robinson Family Initiative for Transformational Research, The Royal Children's Hospital Foundation, University of Toronto McLaughlin Centre., Competing Interests: Declaration of interests APa is a current member of the National Institute of Health and Clinical excellence (NICE) technology appraisal committee B and has a financial interest in Genedrive PLC. KW has consulted for Stoke Therapeutics. JHC has received renumeration for lectures by GW pharma/Jazz, UCB/Zogenix, Biocodex, and Biogen; is a member of the Data Monitoring and Safety Committee for Admiral Trial (Stroke Therapeutics); and is Chair of the Medical Advisory Board for Matthews Friends, Dravet UK, and Hope for Hypothalamic Hamartoma. IES has served on scientific advisory boards for BioMarin, Chiesi, Eisai, Encoded Therapeutics, GlaxoSmithKline, Knopp Biosciences, Nutricia, Rogcon, Takeda Pharmaceuticals, UCB, and Xenon Pharmaceuticals; has received speaker honoraria from GlaxoSmithKline, UCB, BioMarin, Biocodex, Chiesi, Liva Nova, Nutricia, Zuellig Pharma, and Eisai; has received funding for travel from UCB, Biocodex, GlaxoSmithKline, Biomarin, Encoded Therapeutics, and Eisai; has served as an investigator for Anavex Life Sciences, Cerecin, Cerevel Therapeutics, Eisai, Encoded Therapeutics, EpiMinder, Epygenyx, ES-Therapeutics, GW Pharma, Marinus, Neurocrine BioSciences, Ovid Therapeutics, Takeda Pharmaceuticals, UCB, Ultragenyx, Xenon Pharmaceuticals, Zogenix, and Zynerba; and has consulted for Care Beyond Diagnosis, Epilepsy Consortium, Atheneum Partners, Ovid Therapeutics, UCB, Zynerba Pharmaceuticals, BioMarin, Encoded Therapeutics, and Biohaven Pharmaceuticals; and is a Non-Executive Director of Bellberry and a Director of the Australian Academy of Health and Medical Sciences and the Australian Council of Learned Academies. IES might accrue future revenue on pending patent WO61/010176 (filed in 2008; therapeutic compound); has a patent for SCN1A testing held by Bionomics and licensed to various diagnostic companies; has a patent molecular diagnostic or theranostic target for benign familial infantile epilepsy (PRRT2; 2011904493, 2012900190, and PCT/AU2012/001321 [TECH ID:2012-009]). GC has received honorarium from CADTH and serves as the Co-Lead of the Can-GARD Initiative and on the SickKids Precision Child Health steering committee. APo serves on the scientific advisory boards for TevardBio and Syngap Research Fund, and on the American Epilepsy Society Board of Directors. KBH has received support from RogCon Biosciences and Praxis Precision Medicines. AM has received consulting fees from Rocket Pharmaceuticals; honorarium from Jazz Pharmaceuticals; support for attending conferences from Jazz Pharmaceuticals and European Paediatric Neurology Society; fees for participating on boards for Biogen and Biocodex; and serves unpaid roles on the ILAE Genetic Literacy Task Force, EPICARE, and Great Ormond Street Hospital National Institute for Health and Care Research Biomedical Research Centre Chair of Junior Faculty. All other authors declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

Introduction: Primary mitochondrial diseases (PMDs) comprise a large and heterogeneous group of genetic diseases that result from pathogenic variants in either nuclear DNA (nDNA) or mitochondrial DNA (mtDNA). Widespread adoption of next-generation sequencing (NGS) has improved the efficiency and accuracy of mtDNA diagnoses; however, several challenges remain., Areas Covered: In this review, we briefly summarize the current state of the art in molecular diagnostics for mtDNA and consider the implications of improved whole genome sequencing (WGS), bioinformatic techniques, and the adoption of long-read sequencing, for PMD diagnostics., Expert Opinion: We anticipate that the application of PCR-free WGS from blood DNA will increase in diagnostic laboratories, while for adults with myopathic presentations, WGS from muscle DNA may become more widespread. Improved bioinformatic strategies will enhance WGS data interrogation, with more accurate delineation of mtDNA and NUMTs (nuclear mitochondrial DNA segments) in WGS data, superior coverage uniformity, indirect measurement of mtDNA copy number, and more accurate interpretation of heteroplasmic large-scale rearrangements (LSRs). Separately, the adoption of diagnostic long-read sequencing could offer greater resolution of complex LSRs and the opportunity to phase heteroplasmic variants.

Objectives: To develop a flexible droplet digital PCR (ddPCR) workflow to perform non-invasive prenatal diagnosis via relative mutation dosage (RMD) for maternal pathogenic variants with a range of inheritance patterns, and to compare the accuracy of multiple analytical approaches., Methods: Cell free DNA (cfDNA) was tested from 124 archived maternal plasma samples: 88 cases for sickle cell disease and 36 for rare Mendelian conditions. Three analytical methods were compared: sequential probability ratio testing (SPRT), Bayesian and z-score analyses., Results: The SPRT, Bayesian and z-score analyses performed similarly well with correct prediction rates of 96%, 97% and 98%, respectively. However, there were high rates of inconclusive results for each cohort, particularly for z-score analysis which was 31% overall. Two samples were incorrectly classified by all three analytical methods; a false negative result predicted for a fetus affected with sickle cell disease and a false positive result predicting the presence of an X-linked IDS variant in an unaffected fetus., Conclusions: ddPCR can be applied to RMD for diverse conditions and inheritance patterns, but all methods carry a small risk of erroneous results. Further evaluation is required both to reduce the rate of inconclusive results and explore discordant results in more detail., (© 2023 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd.)