Best Practices for Clinical Whole Genome Sequencing

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Questions and Answers

What should genotype-driven analyses aim to capture regarding variants?

Genotype-driven analyses should aim to capture all variants that may be classified as pathogenic or likely pathogenic.

What types of variants are prioritized during the analysis of multiple family members?

Variants suspected based on their inheritance pattern, such as de novo variants or biallelic rare variants, are prioritized.

Why are clinical laboratories encouraged to include analysis of genes not yet linked to disease?

Including such analysis may help in discovering novel disease genes and aid in understanding genotype-phenotype correlations.

What challenges exist in the automated prioritization of pathogenic variants?

<p>Automated prioritization can be challenging due to the unstructured nature of the scientific literature.</p> Signup and view all the answers

How can software tools assist analysts in identifying variants with disease associations?

<p>Software tools can identify variants previously reported in association with any phenotype using literature searches or database entries.</p> Signup and view all the answers

What role does the ClinVar database play in genotype-phenotype analysis?

<p>ClinVar serves as a critical database for reporting variants associated with phenotypes.</p> Signup and view all the answers

What types of variants are highlighted in automated prioritization based on gnomAD constraint scores?

<p>Automated prioritization focuses on de novo and pLOF variants in highly constrained genes.</p> Signup and view all the answers

How should genotype-driven analysis be supplemented for comprehensive results?

<p>Genotype-driven analysis should be supplemented with additional phenotype-driven analyses.</p> Signup and view all the answers

What is the importance of phenotype-driven and genotype-driven filtering strategies in reviewing single nucleotide variants?

<p>These strategies are crucial for identifying unanticipated genetic diagnoses that may explain patient phenotypes.</p> Signup and view all the answers

What are the potential outcomes from applying an unbiased analysis approach to variant detection?

<p>Outcomes include discovering unexpected genetic diagnoses and understanding rare presentations of established disorders.</p> Signup and view all the answers

Why is it important to consider all possible consequences of single nucleotide variants?

<p>Considering all consequences, like splicing annotations and transcript-specific impacts, is vital for accurate interpretation of variant effects.</p> Signup and view all the answers

What types of genetic diagnoses can be revealed through the analysis of single nucleotide variants?

<p>Multiple genetic diagnoses, variants relevant to secondary phenotypes, and those linked to family history of disease can be revealed.</p> Signup and view all the answers

What role do resources like ClinGen play in the identification of high-frequency variants?

<p>ClinGen assembles resources that aid in identifying pathogenic high-frequency variants to ensure they are thoroughly reviewed.</p> Signup and view all the answers

What is meant by phenotypic expansion in the context of variant analysis?

<p>Phenotypic expansion refers to identifying patients with unusual presentations of established disorders mediated by genetic variants.</p> Signup and view all the answers

What are the implications of finding clinically significant incidental or secondary findings?

<p>Clinically significant findings can inform patient management and preventative strategies for conditions not initially suspected.</p> Signup and view all the answers

What challenges are associated with multi-allelic variants in single nucleotide variant analysis?

<p>Multi-allelic variants present challenges in determining the significance of each allele's contribution to the patient's phenotype.</p> Signup and view all the answers

What is the primary advantage of whole genome sequencing (WGS) compared to other sequencing methods?

<p>WGS allows detection of a broad range of variant types in a single assay, making it more comprehensive.</p> Signup and view all the answers

What types of genetic variants can be detected by whole genome sequencing?

<p>WGS can detect single nucleotide variants (SNV), small insertions and deletions, mitochondrial variants, repeat expansions, copy number variants, and structural variants.</p> Signup and view all the answers

How does WGS ensure uniform coverage of genomic regions?

<p>WGS is untargeted, resulting in more uniform coverage of exonic regions and added coverage of intronic, intergenic, and regulatory regions.</p> Signup and view all the answers

What was the purpose of the Medical Genome Initiative's working group?

<p>The working group aimed to establish best practice recommendations for the interpretation and reporting of clinical diagnostic WGS.</p> Signup and view all the answers

What discrepancy was noted between whole exome sequencing (WES) and whole genome sequencing (WGS) in the recent meta-analysis?

<p>The meta-analysis found no significant difference in yields between WES and WGS.</p> Signup and view all the answers

What methods were used to guide the discussions and development of the best practice recommendations?

<p>Informal polling during teleconference meetings was used to gather insights from participating laboratories.</p> Signup and view all the answers

What should newly issued test requisition forms indicate regarding genetic variants?

<p>They should indicate that genetic variants relevant to newly published variant or gene-level evidence may allow a previously unreviewed variant to meet criteria for expert review.</p> Signup and view all the answers

What are some of the key areas that lack consensus in the adoption of WGS?

<p>Areas lacking consensus include requisition/consent, data annotation, analysis, triage, variant curation, reporting, and reanalysis.</p> Signup and view all the answers

How might laboratories suggest a time period for reanalysis of genetic tests?

<p>Laboratories may suggest a minimum time period, such as one year, to have elapsed since the initial analysis before conducting a reanalysis.</p> Signup and view all the answers

Why might comparisons between cohorts in genetic sequencing be limited in utility?

<p>Comparisons may be limited due to variability introduced by factors such as patient age groups, clinical indications, and family structures.</p> Signup and view all the answers

What triggers reactive reanalysis in a laboratory setting?

<p>Reactive reanalysis is triggered when a request is made by the ordering provider or patient.</p> Signup and view all the answers

In what way can reanalysis be initiated proactively?

<p>Proactive reanalysis can be initiated by new publications, updated transcripts, new gene models, or changes in the WGS test definition.</p> Signup and view all the answers

What is the importance of clarifying phenotypic data before testing?

<p>Clarifying phenotypic data ensures that laboratory staff can accurately assess and interpret the relevance of the information prior to initiating testing.</p> Signup and view all the answers

What is the role of policies regarding secondary findings in genetic testing?

<p>Policies for secondary findings analysis should be developed in advance to define how incidental findings will be reported and managed.</p> Signup and view all the answers

What should requisition and consent forms clarify for trio or multiple-family member sequencing?

<p>They should clarify how the data from auxiliary family members will be used and reported.</p> Signup and view all the answers

Why is proactive reanalysis recognized as an important step in WGS testing?

<p>Proactive reanalysis is recognized as important because it maximizes the clinical utility of WGS tests through updates from new clinical information.</p> Signup and view all the answers

What is the recommended process for reviewing monoallelic variants in autosomal recessive genes?

<p>A compelling monoallelic variant in an autosomal recessive gene should be re-examined by at least two trained staff members.</p> Signup and view all the answers

Why is it important for automated analysis tools to be assessed by human analysts?

<p>The sensitivity and specificity of automated analysis tools are insufficient, necessitating careful review by human analysts before reporting.</p> Signup and view all the answers

What should be included in laboratory policies regarding findings considered for return?

<p>Policies should define the types of findings to return and ensure they are available to both patients and providers.</p> Signup and view all the answers

What tools are recommended for systematic proactive reanalysis of variants?

<p>Tools that automatically identify new scientific literature relevant to previously reviewed variants and genes are recommended.</p> Signup and view all the answers

How should results from automated analyses be handled before reporting?

<p>Results from automated analyses should be carefully assessed by a human analyst prior to consideration for reporting.</p> Signup and view all the answers

What is the goal of the laboratory's reporting policies?

<p>The goal is to maximize the diagnostic potential of tests while minimizing the number of variants of uncertain significance reported.</p> Signup and view all the answers

What type of evidence should be addressed when returning variant findings?

<p>Variant-level evidence, gene-level evidence, and the correlation between the patient’s phenotype and the gene should be addressed.</p> Signup and view all the answers

Why is open communication encouraged between ordering providers and the laboratory?

<p>Open communication is encouraged, especially for challenging cases, to clarify uncertainties regarding how findings align with patient phenotypes.</p> Signup and view all the answers

What is the primary role of automated phenotyping in clinical genome sequencing?

<p>Automated phenotyping assists in identifying genetic diseases by analyzing electronic health records to match clinical features with genotypes.</p> Signup and view all the answers

What are copy-number variants and why are they significant in genetic disorders?

<p>Copy-number variants (CNVs) are alterations in the number of copies of a particular gene or region of the genome, significant for their role in various genetic disorders including developmental delays and congenital anomalies.</p> Signup and view all the answers

How does Face2Gene facilitate the identification of genetic syndromes?

<p>Face2Gene uses facial recognition technology to analyze facial features and identify potential congenital dysmorphic syndromes based on visual phenotypes.</p> Signup and view all the answers

What is the significance of structural variation reference in medical genetics?

<p>A structural variation reference is crucial for understanding genetic diversity and the impact of different structural variants on health in both medical and population genomics.</p> Signup and view all the answers

What are the main challenges in detecting long-read assemblies from short-read genome sequencing technologies?

<p>Challenges include accurately identifying complex structural variants and resolving repetitive regions in the genome that short reads struggle to represent.</p> Signup and view all the answers

Why is the Human Disease Ontology significant in genetic research?

<p>The Human Disease Ontology provides a standardized framework for classifying and organizing disease-related information, facilitating better communication and data sharing in genetic research.</p> Signup and view all the answers

Describe the ethical considerations involved in handling incidental findings in genetic testing.

<p>Ethical considerations include the obligation to inform patients about incidental findings that could have health implications, and the need to balance this with the patient’s right not to know.</p> Signup and view all the answers

What role do guidelines such as those from ACMG/AMP play in mitochondrial DNA variant interpretation?

<p>ACMG/AMP guidelines provide a standardized approach for evaluating the clinical significance of mitochondrial DNA variants, ensuring consistency in genetic counseling and diagnosis.</p> Signup and view all the answers

Flashcards

What is Whole Genome Sequencing (WGS)?

Whole Genome Sequencing (WGS) is a powerful technique that allows scientists to analyze the complete DNA sequence of an organism, offering a comprehensive view of an individual's genetic makeup. It provides a more detailed picture of variations compared to targeted sequencing, enabling the detection of a wide range of genetic alterations like SNVs, insertions, deletions, mitochondrial variants.

What are the benefits of WGS over other genetic testing?

WGS goes beyond just looking at genes, it also analyzes non-coding regions (introns, intergenic regions) which may play important roles in regulating gene expression and disease development.

What types of genetic variations can WGS detect?

WGS allows the detection of a broader range of variants, including small insertions and deletions, mitochondrial variants, repeat expansions, copy number variants, and other structural variants.

How is WGS used in diagnostics?

WGS can be used to diagnose a wide range of genetic disorders, including rare and complex conditions, by identifying disease-causing mutations.

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How does WGS contribute to personalized medicine?

WGs provides a comprehensive overview of an individual's genetic makeup, allowing for personalized medicine approaches.

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Who is working to standardize WGS for clinical use?

The Medical Genome Initiative (MGI) has formed a working group to establish best practice recommendations for interpreting WGS data for clinical diagnostics.

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What are the key areas of focus for the MGI working group?

MGI's working group is focusing on areas like data annotation, analysis, variant curation, reporting, and reanalysis to improve the accuracy and accessibility of WGS for clinical use.

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Why are best practice recommendations for WGS important?

Addressing the challenges and establishing best practices for WGS data interpretation are essential for increasing its adoption in routine clinical practice.

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Single Nucleotide Variants (SNVs)

Variations in a single nucleotide that are the most common type of genetic change. These variations are often reviewed for their potential impact on health.

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Phenotype-driven filtering

A process of selecting and analyzing genetic variations based on the patient's symptoms or family history.

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Genotype-driven filtering

A process of selecting and analyzing genetic variations based on known genetic associations or databases.

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Multi-allelic variants

Variants that occur at the same position in the genome but have different alternate alleles. This means a single position can have multiple potential variations.

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Splicing annotations

A type of genetic variation that affects the splicing process, which is important for creating functional proteins from DNA.

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High frequency variants

Genetic variations that have a high frequency in the population.

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ClinGen and GeT-RM

Resources that gather information and standards for interpreting genetic variations.

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Low penetrance, risk, and other high frequency variants

Variations that are less likely to cause significant health effects, but may still play a role in individual health. These variations may be associated with increased risk of certain diseases.

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Genotype-Driven Analysis

A type of analysis focusing on genetic changes linked to known diseases, including previously reported variants and predicted loss of function variants.

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Predicted Loss of Function (pLOF) Variant

A special type of variant that disrupts a gene's function by altering the protein it codes for.

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Gene Discovery Analysis

A gene analysis method that looks for new disease genes in individuals with specific symptoms, even if those genes haven't been linked to the disease before.

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ClinVar

A database containing information about genetic variations and their link to diseases.

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gnomAD

A database that catalogs the frequency of different genetic variants within populations.

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Phenotype-Driven Analysis

An analysis that uses information about a patient's health condition or symptoms to guide the search for potential genetic explanations.

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Judicious Reporting

A process where labs carefully consider reporting genetic findings that might be related to disease but haven't been firmly established, based on the best available evidence.

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De Novo Variant

A genetic variant that is present in only one copy of a gene.

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Copy Number Variant (CNV)

A genetic variation where a segment of DNA is duplicated or deleted, potentially leading to changes in gene expression or function.

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Re-examination of Calls

A process of checking all identified genetic changes for potential health impact, using both genetic and clinical information.

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Proactive Reanalysis

A process where genetic data is automatically compared with newly published scientific information to identify potential updates and revisions.

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Human Analyst Assessment

A process of carefully analyzing and reviewing the results of genetic testing by a trained expert to ensure accuracy and reliability.

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Reporting Policies

A formal decision-making process to determine which genetic findings are considered significant and should be reported to patients and healthcare providers.

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Variant Penetrance

The ability of a genetic variant to cause a health condition, considering its impact on gene function and the likelihood of disease development.

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Open Reporting Communication

Sharing information about genetic test results and their potential implications with both patients and their healthcare providers.

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Reanalysis of WGS data

The process of reviewing previously analyzed genetic data from whole genome sequencing (WGS) for newly published genetic information and updated databases. This allows for a more comprehensive understanding of individual genetic variations and their potential impact on health.

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Minimum time period for reanalysis

The practice of considering a minimum time period (e.g., one year) to pass between the initial analysis of WGS data and a subsequent reanalysis. This ensures that enough new information is generated to warrant a review.

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Trio sequencing

The use of information from multiple family members, such as a trio (parents and child), to identify genetic variants that are specific to a particular individual.

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Phenotype information

Detailed information about an individual's physical traits, medical history, and other relevant factors that can be used to interpret genetic findings.

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Policies for secondary findings reporting in WGS

Policies and procedures that clarify how laboratories will handle incidental findings, which are genetic variations that are not related to the primary reason for the genetic test but could have clinical significance.

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Informed consent for phenotypic data

Informed consent forms that clearly outline the uses of phenotypic information.

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Copy-number variants (CNVs)

A type of genetic variation that involves changes in the number of copies of a DNA segment. This can affect gene dosage and lead to genetic disorders.

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Whole-genome sequencing (WGS)

A laboratory technique used to analyze the complete DNA sequence of an organism. It provides a comprehensive view of an individual's genetic makeup.

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PhenoTips

A software tool that allows healthcare professionals to gather and analyze patient information, including medical history, symptoms, and physical characteristics.

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Study Notes

Best Practices for Clinical Whole Genome Sequencing

  • Whole genome sequencing (WGS) is emerging as a first-tier diagnostic test for rare genetic disorders, offering a more comprehensive approach than whole exome sequencing or other targeted sequencing assays.
  • WGS is superior because it can detect a broader range of variant types like single nucleotide variants (SNVs), insertions/deletions, mitochondrial variants, repeat expansions, copy number variants (CNVs) and other structural variants (SVs) within a single assay. It also provides more uniform coverage of exonic regions and intronic, intergenic, and regulatory regions.
  • The Medical Genome Initiative (MGI) developed best practice recommendations for WGS interpretation and reporting, focusing on the interpretation and reporting of clinical diagnostic WGS.

Clinical Diagnostic Genomic Sequencing Phases

  • Analysis is divided into three phases:
    • Primary analysis: technical components of the assay like DNA extraction, library preparation, sequence generation, and preliminary data quality control (QC)
    • Secondary analysis: bioinformatic processes such as aligning raw sequence data to a genome reference, variant calling, and other similar processes
    • Tertiary analysis: includes annotation, filtering, prioritization, classification of variants, case interpretation, and reporting.

Interpretation and Reporting Considerations for Clinically Relevant Variants

  • Single Nucleotide Variants (SNVs): require phenotype-driven and genotype-driven filtering, considering splicing, transcript-specific impacts, and multi-nucleotide variants (MNVs).
  • Small Insertions/Deletions (indels): Validation and orthogonal confirmation might be needed for accuracy, prioritizing quality, frequency, and overlap with protein-coding regions.
  • Copy Number Variation (CNV): Filtering based on quality, frequency, and overlap with protein-coding regions, and using inheritance and copy number review during triaging. Review of the depth-based plot and B-allele frequency plot across the genome to identify large CNVs is crucial.
  • Balanced and Complex Structural Variants (SV): Primarily used for identifying recurrent pathogenic balanced structural variants, refining CNVs, directed SV searches in known regions, and investigating runs of homozygosity (ROH).
  • Runs of Homozygosity (ROH): Extensive ROH on a chromosome can indicate uniparental disomy (UPD), while ROH across chromosomes may be due to consanguinity.
  • Repeat Expansions: Emphasizes orthogonal testing for repeat length confirmation and visual alignment inspection to confirm allele expansions and identify interruptions.
  • Mitochondrial Variants: Focuses on heteroplasmy, heteroplasmy thresholds for disease manifestation, variable inter- and intra-familial phenotype expressivity, and sample origin variations.
  • Mosaic Variants: Lower WGS coverage compared to WES or panel testing, indicating a need for orthogonal testing.
  • Polygenic Risk Scores (PRS): Should specify ancestry for calculations and acknowledge any limitations based on ancestry in interpretation.

Reanalysis

  • Periodic case reanalysis is recommended to improve the diagnostic yield.
  • Reanalysis policies should be established in advance and communicate to providers during test ordering.

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