# Datamodel


This documentation is a work in progress and is not currently up to date.

Please contact developers for more details.

The datamodel is defined using SQLAlchemy (opens new window), and the implementation can be found in src/vardb/datamodel/.

The main concepts of the datamodel are described below. For a complete list of tables and fields, check the code.

# Introduction

The variants are interpreted in a stepwise workflow, either one variant at a time or several ones in an analysis. An analysis is the set of variants that are found in a patient sample using a gene panel as variant filter. From one sample there can be multiple analyses, one for each gene panel chosen. In a workflow the work is done across several interpretations, with the last being finalized (usually) by a different user than the ones having done the previous interpretations. The previous interpretations are marked for review. The workflow goes through start-review-finalize phases.

When a workflow is finalized one or several assessments are either reused or created. The result and context of each step is captured in a snapshot enabling time-travelling. The assessment includes a classification (1-5). A description intended for the referring doctor is persisted as a report. The references relevant for the assessment is captured separately in a reference assessment. When interpreting variants in an analysis it's common practice to reuse assessments and reports made earlier.

# Common features

To enable time-travelling and auditing, data is generally not over-written. Instead copies are made and old and new entities are linked together.

To implement this most models have these fields:

  • Date of creation
  • Date when the object became superceded
  • The id of the new object that "replaces" it

Models with previous/current semantics are:

  • Annotations
  • Allele assessments
  • Reference assessments
  • Allele report
  • Reference assessments

# Genetic data and annotation

Genetic data, currently genetic variation represented as SNVs and indels, are stored in the allele table.

# Allele

An allele (opens new window) is a variant form of a gene. It's among the most important objects in the model. If combined with an annotation it can exists in isolation.

An allele has:

  • Reference genome version
  • Chromosome
  • Start and stop position
  • Change from/to
  • Change type (snv, ins, del, indel)
  • Original vcf entries (REF, ALT, POS)

# Annotation

The annotation contains information about a single allele's population frequencies, predicted effects and various other data from external databases. Annotation can change often, and whenever it is updated, the previous annotation is archived. There is therefore only one current annotation for each allele. However, the current annotation points to previous ones to keep track of historic annotations.

ELLA relies on a separate annotation service to annotate data. ella-anno (opens new window), to annotate and import data; see Production and the separate documentation (opens new window). The annotation has:

  • The actual annotation data (json)
  • Link to an allele

The user-generated annotation (called custom annotation) is separate from that generated by the pipeline.

# AnnotationShadow

In order to aid performance when filtering and searching, parts of the annotation JSON data are shadowed into separate tables. These tables are updated by triggers on the annotation table and should never be modified manually. They only contain data for the latest annotation for an allele. They have indexes on more or less all columns.

Currently there are two such tables: annotationshadowtranscript and annotationshadowfrequency.

# Genotype

The pair of alleles is described by the Genotype. If homozygous only one allele is defined.

The genotype is connected to/has:

  • Sample
  • Analysis
  • Genotype quality
  • Variant quality

# Classifications and assessments

The official classification (1-5) and complementary data such as ACMG criteria and comments are stored in AlleleAssessment.

The assessment has:

  • Classification (1-5)
  • Evaluation (json, free tekst and ACMG codes)
  • Link to allele
  • Gene panel
  • Annotation

Assessments with class 3-5 are valid for a limited period of time before a new interpretation is required. The date created field of AlleleAssessment is thus critical.

# AlleleReport

The information sent to doctors for each variant/allele is kept separate from the assessment itself. The report can be updated without changing i.e. the classification.

The allele report has:

  • Free text (json)
  • Link to the assessment

# Reference

A reference to research literature with data such as:

  • Title
  • PubMed ID
  • Abstract

The references can either batch imported using data download from XX or uploaded one-by-one by the user in the tool itself.

# ReferenceAssessment

Assessing a reference is done in the context of a variant and a gene panel. The user can add tags/text the highlight the info that's relevant for the variant being interpreted.

A reference assessment has:

  • Link to reference
  • Link to allele
  • Evaluation (json: text, ACMG codes, tags)

# Analyses and samples

An Analysis is bioinformatic calcalutation producing a list of variants that are to be interpreted. An analysis is done in the context of a specific gene panel used as a basis for variant filtering. The sequencing data is taken from a Sample. The data from a sample can be used in different analyeses, and the database will have a pair of sample/analysis for each. Thus there can be multiple rows for the same physical sample.

An Analysis has:

  • Gene panel
  • A priority (for prioritizing the interpretation work)
  • Various data (like comment, tags)
  • The history of interpretations for the analysis' variants

A Sample:

  • Identifies the physical sample/sequencing data
  • The analysis to be done on the data
  • The source of the sequencing data (Sanger, HTS)
  • Mentions models that have a link to Analysis and why.

# Workflow

In the step-wise process of interpreting variants and analyses, each step/round is saved in either AlleleInterpretation or AnalysisInterpetation. They are very similiar with InterpretationMixin as the common basis, see Mixins (opens new window)

Each round (created when starting, setting to review or finalizing) captures the work of the user (comments, ACMG codes, references assessed etc) and UI-specific properties. We can refer to this data as state (interpretation and ui state?). The info is persisted as a json field called 'state'. Each time the users clicks 'Save' the state field is updated, and the previous state is appended to the list 'state_history' (json).

For each round (clicking Reopen/Review) a new Interpretation is created with the state (and some other fields) copied from the previous Interpretation.

See diagram (S=state, [..] list of previous states):

AnalysisInterpretation: S [] --save--> S' [S] --save--> S'' [S' S] etc
AnalysisInterpretationState':  S'' [] --save--> S''' [S''] --save--> S'''' [S''' S''] etc

In addition to passing the state to a new round, the context of the interpretation is persisted in so-called snapshot objects.

# Interpretation snapshots

The context of each interpretation round is saved in either AnalysisInterpretationSnapshot or AlleleInterpretationSnapshot, depending on the type of worklow.For each allele (in allele workflow there is only one) one snapshot instance is saved.

The context saved in a snapshot:

  • The annotation
  • Custom annotation created by the user
  • The assessment (if any) that already existed and was displayed to user
  • The report (if any) that already existed and was displayed to user

When finalizing the snapshow also contain:

  • The assessment (including the classification) made by the user
  • The reference assessments made by the user
  • The report made by the user

The snapshot is also linked to the interpretation round (AlleleInterpretation or AnalysisInterpretation) having the state info. This enables a time-travelling feature where the tool can show the info that was available at the end of the round.

# Finalizing an interpretation


Last Updated: 12/18/2020, 10:03:27 PM