Evaluation of a novel assay for detection of the fetal marker RASSF1A: facilitating improved diagnostic reliability of noninvasive prenatal diagnosis

BackgroundAnalysis of cell free fetal (cff) DNA in maternal plasma is used routinely for non invasive prenatal diagnosis (NIPD) of fetal sex determination, fetal rhesus D status and some single gene disorders. True positive results rely on detection of the fetal target being analysed. No amplification of the target may be interpreted either as a true negative result or a false negative result due to the absence or very low levels of cffDNA. The hypermethylated RASSF1A promoter has been reported as a universal fetal marker to confirm the presence of cffDNA. Using methylation-sensitive restriction enzymes hypomethylated maternal sequences are digested leaving hypermethylated fetal sequences detectable. Complete digestion of maternal sequences is required to eliminate false positive results.MethodscfDNA was extracted from maternal plasma (n = 90) and digested with methylation-sensitive and insensitive restriction enzymes. Analysis of RASSF1A, SRY and DYS14 was performed by real-time PCR.ResultsHypermethylated RASSF1A was amplified for 79 samples (88%) indicating the presence of cffDNA. SRY real time PCR results and fetal sex at delivery were 100% accurate. Eleven samples (12%) had no detectable hypermethylated RASSF1A and 10 of these (91%) had gestational ages less than 7 weeks 2 days. Six of these samples were male at delivery, five had inconclusive results for SRY analysis and one sample had no amplifiable SRY.ConclusionUse of this assay for the detection of hypermethylated RASSF1A as a universal fetal marker has the potential to improve the diagnostic reliability of NIPD for fetal sex determination and single gene disorders

Implementing Prenatal Diagnosis Based on Cell-Free Fetal DNA: Accurate Identification of Factors Affecting Fetal DNA Yield

Objective: Cell-free fetal DNA is a source of fetal genetic material that can be used for non-invasive prenatal diagnosis. Usually constituting less than 10% of the total cell free DNA in maternal plasma, the majority is maternal in origin. Optimizing conditions for maximizing yield of cell-free fetal DNA will be crucial for effective implementation of testing. We explore factors influencing yield of fetal DNA from maternal blood samples, including assessment of collection tubes containing cell-stabilizing agents, storage temperature, interval to sample processing and DNA extraction method used.Methods: Microfluidic digital PCR was performed to precisely quantify male (fetal) DNA, total DNA and long DNA fragments (indicative of maternal cellular DNA). Real-time qPCR was used to assay for the presence of male SRY signal in samples.Results: Total cell-free DNA quantity increased significantly with time in samples stored in K(3)EDTA tubes, but only minimally in cell stabilizing tubes. This increase was solely due to the presence of additional long fragment DNA, with no change in quantity of fetal or short DNA, resulting in a significant decrease in proportion of cell-free fetal DNA over time. Storage at 4 degrees C did not prevent these changes.Conclusion: When samples can be processed within eight hours of blood draw, K(3)EDTA tubes can be used. Prolonged transfer times in K(3)EDTA tubes should be avoided as the proportion of fetal DNA present decreases significantly; in these situations the use of cell stabilising tubes is preferable. The DNA extraction kit used may influence success rate of diagnostic tests

Delivering genome sequencing in clinical practice: an interview study with healthcare professionals involved in the 100 000 Genomes Project

Objectives: Genome sequencing is poised to be incorporated into clinical care for diagnoses of rare diseases and some cancers in many parts of the world. Healthcare professionals are key stakeholders in the clinical delivery of genome sequencing-based services. Our aim was to explore views of healthcare professionals with experience of offering genome sequencing via the 100 000 Genomes Project. Design: Interview study using thematic analysis. Setting: Four National Health Service hospitals in London. Participants: Twenty-three healthcare professionals (five genetic clinicians and eight non-genetic clinicians (all consultants), and 10 ‘consenters’ from a range of backgrounds) involved in identifying or consenting patients for the 100 000 Genomes Project. Results: Most participants expressed positive attitudes towards genome sequencing in terms of improved ability to diagnose rare diseases, but many also expressed concerns, with some believing its superiority over exome sequencing had not yet been demonstrated, or worrying that non-genetic clinicians are inadequately prepared to discuss genome sequencing results with patients. Several emphasised additional evidence about utility of genome sequencing in terms of both main and secondary findings is needed. Most felt non-genetic clinicians could support patients during consent, as long as they have appropriate training and support from genetic teams. Many stated genetics experts will play a vital role in training and supporting non-genetic clinicians in variant interpretation and results delivery, particularly for more complex cases. Conclusions: Healthcare professionals responsible for delivering clinical genome sequencing have largely positive views about the potential for genome sequencing to improve diagnostic yield, but also significant concerns about practical aspects of offering these tests. Non-genetic clinicians delivering genome sequencing require guidance and support. Additional empirical evidence is needed to inform policy and practice, including how genome compares to exome sequencing; utility of secondary findings; training, in particular of non-genetic health professionals; and mechanisms whereby genetics teams can offer appropriate support to their non-genetics colleagues

Lessons learnt from prenatal exome sequencing

BACKGROUND: Prenatal exome sequencing (ES) for monogenic disorders in fetuses with structural anomalies increases diagnostic yield. In England there is a national trio ES service delivered from two laboratories. To minimise incidental findings and reduce the number of variants investigated, analysis uses a panel of 1205 genes where pathogenic variants may cause abnormalities presenting prenatally. Here we review our laboratory's early experience developing and delivering ES to identify challenges in interpretation and reporting and inform service development. METHODS: A retrospective laboratory records review from 01.04.2020 to 31.05.2021. RESULTS: Twenty-four of 116 completed cases were identified as challenging including 13 resulting in difficulties in analysis and reporting, nine where trio inheritance filtering would have missed the diagnosis, and two with no prenatal diagnosis; one due to inadequate pipeline sensitivity, the other because the gene was not on the panel. Two cases with copy number variants identified were not detectable by microarray. CONCLUSIONS: Variant interpretation requires close communication between referring clinicians, with occasional additional examination of the fetus or parents and communication of evolving phenotypes. Inheritance filtering misses ∼5% of diagnoses. Panel analysis reduces but does not exclude incidental findings. Regular review of published literature is required to identify new reports that may aid classification

Implementing a rapid fetal exome sequencing service: What do parents and health professionals think?

OBJECTIVES: Prenatal exome sequencing (pES) for the diagnosis of fetal abnormalities is being introduced more widely in clinical practice. Here we explore parents' and professionals' views and experiences of pES, to identify perceived benefits, concerns, and support needs. METHODS: Semi-structured interviews were conducted with 11 parents and 20 health professionals (fetal medicine and clinical genetics) with experience of rapid pES prior to implementation in the English National Health Service. Interviews were transcribed verbatim and analysed thematically. RESULTS: Parents and professionals were largely positive about pES, emphasising clinical and psychosocial benefits of a timely, definitive diagnosis in pregnancy. Concerns included parental anxiety related to the timing of pES results or uncertain findings, a need for guidelines for case selection and reporting, and ensuring sufficient capacity for counselling, phenotyping and variant interpretation. Professionals were concerned non-genetics professionals may not be equipped to counsel parents on the complexities of pES. CONCLUSION: These findings highlight important issues for clinical implementation of pES. Expert counselling is required to enable parents to make informed decisions during a stressful time. To achieve this, professionals need further education and training, and fetal medicine and genetics services must work closely together to ensure parental understanding and appropriate support

Parents’ motivations, concerns and understanding of genome sequencing: a qualitative interview study

Abstract: The 100,000 Genomes Project is a hybrid clinical and research project in which patients and parents are offered genome sequencing for cancer and rare and inherited disease diagnosis; all participants receive their main findings and contribute their data for research, and are offered optional secondary findings. Our aim was to explore participating parents’ attitudes towards and understanding of genome sequencing in this hybrid context. We conducted in-depth telephone interviews with 20 parents of children with rare diseases participating in the 100,000 Genomes Project. Parents were positive about contributing to research, although some had needed reassurance about data protections. Although most felt positive about secondary findings, some could not recall or misunderstood key aspects. Some were also concerned about potential emotional impact of results and a few raised concerns about life insurance implications, and the impact of future legal changes. Participants were generally positive about consent appointments, but several raised concerns about ‘information overload’ because of deciding about secondary findings at the same time as about the main diagnostic genome sequencing and data contribution. Additional information resources, particularly online tools, were highlighted as potentially useful ways of supporting the consent process. We conclude that parents offered genome sequencing as part of a national hybrid clinical and research project report many positive attitudes and experiences, but also concerns and misunderstandings. Further research is needed on how best to support informed consent, particularly about secondary findings. Additional resources such as online tools might usefully support future genome sequencing consent processes

Development and mixed-methods evaluation of an online animation for young people about genome sequencing

Abstract: Children and young people with rare and inherited diseases will be significant beneficiaries of genome sequencing. However, most educational resources are developed for adults. To address this gap in informational resources, we have co-designed, developed and evaluated an educational resource about genome sequencing for young people. The first animation explains what a genome is, genomic variation and genome sequencing (“My Genome Sequence”: http://bit.ly/mygenomesequence), the second focuses on the limitations and uncertainties of genome sequencing (“My Genome Sequence part 2”: http://bit.ly/mygenomesequence2). In total, 554 school pupils (11–15 years) took part in the quantitative evaluation. Mean objective knowledge increased from before to after watching one or both animations (4.24 vs 7.60 respectively; t = 32.16, p < 0.001). Self-rated awareness and understanding of the words ‘genome’ and ‘genome sequencing’ increased significantly after watching the animation. Most pupils felt they understood the benefits of sequencing after watching one (75.4%) or both animations (76.6%). Only 17.3% felt they understood the limitations and uncertainties after watching the first, however this was higher among those watching both (58.5%, p < 0.001). Twelve young people, 14 parents and 3 health professionals consenting in the 100,000 Genomes Project reported that the animation was clear and engaging, eased concerns about the process and empowered young people to take an active role in decision-making. To increase accessibility, subtitles in other languages could be added, and the script could be made available in a leaflet format for those that do not have internet access. Future research could focus on formally evaluating the animations in a clinical setting

Evaluation of Allelic Expression of Imprinted Genes in Adult Human Blood

Background: Imprinted genes are expressed from only one allele in a parent-of-origin dependent manner. Loss of imprinted expression can result in a variety of human disorders and is frequently reported in cancer. Biallelic expression of imprinted genes in adult blood has been suggested as a useful biomarker and is currently being investigated in colorectal cancer. In general, the expression profiles of imprinted genes are well characterised during human and mouse fetal development, but not in human adults. Methodology/Principal Findings: We investigated quantitative expression of 36 imprinted genes in adult human peripheral blood leukocytes obtained from healthy individuals. Allelic expression was also investigated in B and T lymphocytes and myeloid cells. We found that 21 genes were essentially undetectable in adult blood. Only six genes were demonstrably monoallelic, and most importantly, we found that nine genes were either biallelic or showed variable expression in different individuals. Separated leukocyte populations showed the same expression patterns as whole blood. Differential methylation at each of the imprinting control loci analysed was maintained, including regions that contained biallelically expressed genes. This suggests in some cases methylation has become uncoupled from its role in regulating gene expression. Conclusions/Significance: We conclude that only a limited set of imprinted genes, including IGF2 and SNRPN, may be useful for LOI cancer biomarker studies. In addition, blood is not a good tissue to use for the discovery of new imprinted genes. Finally, lymphocyte DNA methylation status in the adult may not always be a reliable indicator of monoallelic gene expression

Knowledge, attitudes and decision regret: a longitudinal survey study of participants offered genome sequencing in the 100,000 Genomes Project

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

Participant experiences of genome sequencing for rare diseases in the 100,000 Genomes Project: a mixed methods study

In this mixed methods study, a survey and in-depth interviews were used to explore whether decision regret and the psychological impact of receiving genome sequencing (GS) results differed between parents and patients, and between those who received a genetic diagnosis and those who did not. Participants (n = 77) completed a survey that included the Decisional Regret Scale (DRS) and an adaptation of the Multidimensional Impact of Cancer Risk Assessment (MICRA) at least 12 months after consenting for GS for rare disease diagnosis in the 100,000 Genomes Project. Survey participants were invited to take part in an interview and 39 agreed; 12 with a diagnosis, 5 with variants of uncertain significance, and 19 with no pathogenic findings identified. Both survey and interview findings indicated that decision regret was low. DRS scores revealed no differences in levels of regret between parents and patients, or between those with a diagnosis and those without. Though MICRA scores indicated minimal evidence of negative psychological impacts of receiving GS results, subscale analysis revealed greater distress and uncertainty for parents compared to patients. Receiving a diagnosis was found not to influence MICRA scores, supporting interview findings of both positive and negative emotional and psychological impacts irrespective of a genetic diagnosis. Our findings have implications for policy and practice as GS is integrated into the UK and worldwide; notably, that expectation-setting is critical when offering GS, and that post-test counselling is important regardless of the GS result received, with parents perhaps needing additional emotional support