Strategies for Referent Tracking in Electronic Health Records

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Strategies for Referent Tracking in Electronic
Health Records

• Dr. W. Ceusters
• European Centre for Ontological Research
• Saarland University
• Saarbrücken - Germany

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The story of Jane Smithan old case, well known
in the literature ...
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July 4th, 1990 Jane goes shopping
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A visit to the hospital

• City Health Centre Dr. Peters
• (City HC) Dr. Longley

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Diagnosis a severe spiral fracture of the femur
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The City HCs medical record

• Main principles
• a faithful record of the clinicians
  observations what they have heard, seen, thought
  and done.
• captures in a structured form all of the
  clinically significant information in the
  narrative notes, where by clinically significant
  they mean the information which is within the
  medical domain rather than the domain of everyday
  life.

Rector AL, Nowlan WA, Kay S, Goble CA, Howkins
TJ. A framework for modelling the electronic
medical record. Methods Inf Med. 1993
Apr32(2)109-19.
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City HCs EHR model
Rector AL, Nowlan WA, Kay S, Goble CA, Howkins
TJ. A framework for modelling the electronic
medical record. Methods Inf Med. 1993
Apr32(2)109-19.
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CityHCs representation formalism(for statements
in records)
Categories represent concepts and are analogous
to classes in other formalisms
Individuals concrete instances of categories
which persist in space and time
Occurrences are specific occurrences of
individuals and must be situated in space and
time. The most important group of occurrences are
observations i.e. agents observations of
individuals.
Rector AL, Nowlan WA, Kay S, Goble CA, Howkins
TJ. A framework for modelling the electronic
medical record. Methods Inf Med. 1993
Apr32(2)109-19.
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Mixing statements and entities

• Every occurrence level statement concerning the
  Jane Smiths Fracture of the Femur is an
  observation of the corresponding individual.
• The existence of the individual Jane Smiths
  Fracture of Femur does not imply that Jane Smith
  has, or has ever had, a fracture of the femur,
  but merely that some observation has been made
  about Jane Smith regarding a fracture of the
  femur.
• (The only observation recorded about Jane
  Smiths Fracture of the Femur might be that she
  did not have it.)

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But, there are some problems ...
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Main problem areasfor CityHCs EHR

• Statements refer only very implicitly to the
  concrete entities about which they give
  information.
• Idiosyncracies of concept-based terminologies
• tell us only that some instance of the class the
  codes refer to, is refered to in the statement,
  but not what instance precisely.
• Are usually confused about classes and
  individuals.
• Country and Belgium.
• Mixing up the act of observation and the thing
  observed.
• Mixing up statements and the entities these
  statements refer to.

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Consequences

• Very difficult to
• Count the number of (numerically) different
  diseases
• Bad statistics on incidence, prevalence, ...
• Bad basis for health cost containment
• Relate (numerically same or different) causal
  factors to disorders
• Dangerous public places (specific work floors,
  swimming pools), dogs with rabies, HIV
  contaminated blood from donors, food from
  unhygienic source, ...
• Hampers prevention
• ...

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Proposed solutionReferent Tracking

• Purpose
• explicit reference to the concrete individual
  entities relevant to the accurate description of
  each patients condition, therapies, outcomes,
  ...
• Method
• Introduce an Instance Unique Identifier (IUI) for
  each relevant individual ( particular,
  instance).
• Distinguish between
• IUI assignment for instances that do exist
• IUI reservation for entities expected to come
  into existence in the future

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Ontology

• Ontology the study of being as a science
• An ontology is a representation of some
  pre-existing domain of reality which
• (1) reflects the properties of the objects within
  its domain in such a way that there obtains
  a systematic correlation between reality and the
  representation itself,
• (2) is intelligible to a domain expert
• (3) is formalized in a way that allows it to
  support automatic information processing
• ontological (as adjective)
• Within an ontology.
• Derived by applying the methodology of ontology
• ...

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An ontological analysis
continuants
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Ontological recategorisation
Jane Smiths consultation with Dr. Peters
at City HC on 4th July 1990
Dr. Peters assessment of Jane Smiths fracture
of femur at City HC on 4th July 1990
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Essentials of Referent Tracking

• Generation of universally unique identifiers
• deciding what particulars should receive a IUI
• finding out whether or not a particular has
  already been assigned a IUI (each particular
  should receive maximally one IUI)
• using IUIs in the EHR, i.e. issues concerning the
  syntax and semantics of statements containing
  IUIs
• determining the truth values of statements in
  which IUIs are used
• correcting errors in the assignment of IUIs.

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Architecture of aReferent Tracking System (RTS)

• RTS system in which all statements referring to
  particulars contain the IUIs for those
  particulars judged to be relevant.
• Ideally set up as broad as possible
• some metrics
• of particulars referred to by means of IUI
• of HCs active in a region
• Geographic region
• functional region defined by contacts amongst
  patients
• of patients referred to within a region
• Services
• IUI generator
• IUI repository statements about assignments and
  reservations
• Referent Tracking Database (RTDB) index (LSID)
  to statements relating instances to instances and
  classes

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IUI generation

• Universally Unique IDs
• recently standardized through ISO/IEC
  9834-82004,
• specifies format and generation rules enabling
  users to produce 128-bit identifiers that are
  either guaranteed or have a high probability of
  being globally unique
• Meaningless strings
• Central management or certification not needed to
  guarantee uniqueness
• (But use as IUI requires this)

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IUI asignment

• an act carried out by the first cognitive
  agent feeling the need to acknowledge the
  existence of a particular it has information
  about by labelling it with a UUID.
• cognitive agent
• A person
• An organisation
• A device or software agent, e.g.
• Bank note printer,
• Image analysis software.

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Criteria for IUI assignment (1)

• The particulars existence must be determined
• Easy for persons in front of you, body parts, ...
• Easy for planned acts they do not exist before
  the plan is executed !
• Only the plan exists and possibly the statements
  made about the future execution of the plan
• More difficult subjective symptoms
• But the statements the patient makes about them
  do exist !
• However
• no need to know what the particular exactly is,
  i.e. which universal it instantiates
• No need to be able to point to it precisely
• One bee out of a particular swarm that stung the
  patient, one pain out of a series of pain attacks
  that made the patient worried, one out of 2
  electrons in a Györgys box
• But this is not a matter of choice, not any
  out of ...

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Criteria for IUI assignment (2)

• The particulars existence may not already have
  been determined as the existence of something
  else
• Morning star and evening star
• Himalaya
• Multiple sclerosis
• May not have already been assigned a IUI.
• It must be relevant to do so
• Personal decision, (scientific) community
  guideline, ...
• Possibilities offered by the EHR system
• If a IUI has been assigned by somebody, everybody
  else making statements about the particular
  should use it

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Assertion of assignments

• IUI assignment is an act of which the execution
  has to be asserted in the IUI-repository
• ltda, Ai, tdgt
• da IUI of the registering agent
• Ai the assertion of the assignment ltpa, pp, tap,
  cgt
• pa IUI of the author of the assertion
• pp IUI of the particular
• tap time of the assignment
• c optional description for identification
• td time of registering Ai in the IUI-repository
• Neither td or tap give any information about when
  pp started to exist ! That might be asserted in
  statements providing information about pp .

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Management of the IUI-repository

• Adequate safety and security provisions
• Access authorisation, control, read/write, ...
• Pseudonymisation
• Deletionless but facilities for correcting
  mistakes.
• Registration of assertion ASAP after IUI
  assignment
• (virtual, e.g. LSID) central management with
  adequate search facilities.

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Representation in the EHR

• Relevant particulars referred to using IUIs
• Relationships that obtain between particulars at
  time t expressed using relations from an ontology
  (type OBO)
• Statements describing for each particular, at
  time t
• Of what universal from an ontology it is an
  instance of
• AND/OR (if one insists)
• By means of what concept from a concept-based
  system it can sensibly be described

particulars
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PTP statements - particular to particular

• ordered sextuples of the form ltsa, ta, r,
  o, P, trgt

sa is the IUI of the author of the statement,
ta a reference to the time when the statement
is made, r a reference to a relationship
(available in o) obtaining between the
particulars referred to in P, o a reference to
the ontology from which r is taken, P an ordered
list of IUIs referring to the particulars between
which r obtains, and, tr a reference to the
time at which the relationship obtains.

• P contains as much IUIs as required by the
  arity of r. In most cases, P will be an ordered
  pair such that r obtains between the particular
  represented by the first IUI and the one referred
  to by the second IUI.
• As with A statements, these statements must
  also be accompanied by a meta-statement capturing
  when the sextuple became available to the
  referent tracking system.

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PTCL statements particular to class
ltsa, ta, inst, o, p, cl, trgt sa is the IUI of
the author of the statement, ta a reference to
the time when the statement is made, inst a
reference to an instance relationship available
in o obtaining between p and cl, o a
reference to the ontology from which inst and cl
are taken, p the IUI referring to the
particular whose inst relationship with cl is
asserted, cl the class in o to which p enjoys
the inst relationship, and, tr a reference to
the time at which the relationship obtains.
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PTCO statements particular to concept code
ltsa, ta, cbs, p, co, trgt sa is the IUI of the
author of the statement, ta a reference to the
time when the statement is made, cbs a
reference to the concept-based system from which
co is taken, p the IUI referring to the
particular which the author associates with
co, co the concept-code in cbs which the author
associates with p, and, tr a reference to the
time at which the author considers the
association appropriate,
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Interpretation ofPTCO statements

• must be interpreted as simple indexes to terms in
  a dictionary.
• All that such a statement tells us, is that
  within the linguistic and scientific community in
  which cbs is used, the terms associated with co
  may - i.e. are acceptable to - be used to denote
  p in their determinative version.

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A SNOMED-CT example

• ltIUI-0945, 18/04/2005, SNOMED-CT v0301,
  IUI-1921, 367720001, forevergt
• IUI-0945 author of the statement
• IUI-1921 the left testicle of patient
  IUI-78127
• 367720001 the SNOMED concept-code to which left
  testis is (in SNOMED) attached as term
• So we can denote IUI-1921 by means of
• that left testis
• that entire left testis
• that testicle, that male gonad, that testis
• that genital structure
• that physical anatomical entity
• BUT NOT that SNOMED-CT concept

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Pragmatics of IUIs in EHRs

• IUI assignment requires an additional effort
• In principle no difference qua (or just a little
  bit more) effort compared to using directly codes
  from concept-based systems
• A search for concept-codes is replaced by a
  search for the appropriate IUI using exactly the
  same mechanisms
• Browsing
• Code-finder software
• Auto-coding software (CLEF NLP software Andrea
  Setzer)
• With that IUI comes a wealth of already
  registered information
• If for the same patient different IUIs apply, the
  user must make the decision which one is the one
  under scrutiny, or whether it is again a new
  instance
• A tranfert or reference mechanism makes the
  statements visible through the RTDB

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Advantage betterreality representation
IUI-003
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Other Advantages

• mapping as by-product of tracking
• Descriptions about the same particular using
  different ontologies/concept-based systems
• Quality control of ontologies and cbs
• Systematic inconsistent descriptions in or
  cross terminologies may indicate poor definition
  of the respective terms

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Conclusion

• Referent tracking can solve a number of problems
  in an elegant way.
• Existing (or emerging) technologies can be used
  for the implementation.
• Old technologies (cbs) can play an interesting
  role.
• Big Brother feeling is to be expected but with
  adequate measures easy to fight.
• The proof of the pudding is in the eating
• Pilote is going to be set up