1. The document proposes a revised electronic medical record data model consisting of assessment objects, management objects, and encounters as the central class. 2. Encounters would contain assessment and management objects and stack together to form episodes of care and disease courses. 3. The model simplifies previous structures and provides a common format for sharing data between different software languages, while allowing flexibility for individual software providers.

1. REVISED ELECTRONIC MEDICAL RECORD DATA MODEL
By M W MAIR, Ophthalmic Surgeon, Timaru, New Zealand
This is a response to The Electronic Medical Record Data Model posted by
the NZHIF.
The model for discussion is found at:
http://fims-www.massey.ac.nz/~jpastor/emr/emr_model/sld001.htm
It sets out the objects and some relationships between them for the proposed
national EMR system.
At a meeting between myself (representing the Association of Salaried
Medical Specialists), Ashwin Patel (representing the Royal New Zealand
College of General Practitioners) and the Chairman of the NZHIF Jose
Pastor Urban some simplification of the model was proposed which I have
represented diagrammatically below.
Assessment Objects
Address Contact Demography EG. General History
NPI Family History
Health Care user Examination
Diagnosis….
The ‘S O A (subjective
ENCOUNTER Objective/Assessment
Medical Assessment Part of the SOAP unit
Warning Donor
Management Management Objects
EG Procedures
Pharmaceutical,
Pharmacy referral Waiting time event The ‘P’ or Plan part of
the ‘ S O A P’ unit.
In the re-arranged model, the ‘Assessment/Management’ unit or Encounter
is seen as the central class. The other objects have symmetrical or
asymmetrical relationships with it. The ‘Medical’ Objects themselves are
grossly classified into ‘Assessment’ Objects and ‘Management’ Objects,
which is a further simplification of the SOAP unit
(Subjective/Objective/Assessment/Plan). It was envisaged that ALL contacts

2. between Healthcare Providers and clients could be modeled in this way
including In Patient contacts.
A stack of such encounters with a particular provider or organization would
constitute an ‘Episode of Care’.
A stack of such encounters which was coterminous with the Natural History
of a disease process would constitute a ‘Disease Course’. A ‘Disease
Course’ and an ‘Episode of Care’ would often be coterminous.
Diagram of Two Episodes of Care, One Disease Course
Episode of Care
Episode of Care
Assessment
Objects Disease Course
Management
Objects
A three dimensional diagram of the progression of ‘Encounters’ into
‘Episodes of care’ and ‘Disease Courses’ is shown above. This picture
does not show all the Administrative Objects (such as demographic
details, NPI etc.) which are ‘hung off’ each encounter, for simplicity.
It shows within the ‘Assessment’ and ‘Management’ sections of each
‘Encounter’ an undifferentiated “heap” of medical object instances.
These are the raw data, collected at each encounter. They are
structured into screens and protocols by the end users software, and
the ‘Standard’ does not dictate how those structures should be.

3. Summary
We have been able to agree on a simple structure for the New Zealand
Medical Record Data Model which is diagrammed above.
1.The Objects in the Term Dictionary form a currency for transactions, and
serve more than one purpose. They contain (as Object Instances) the
data collected during ‘Encounters’; they can be used for
epidemiological research; they can be used for accounting and audit.
2.The Standard would specify a common format for objects, which can be
shared between different languages eg C++, Smalltalk, Fox 5, etc, and
suggests that the medical objects are segregated into ‘Assessment’
objects and ‘Management’ objects. This means that there will be a
dated cluster of object instances corresponding to each encounter.
3.The Standard itself should not further structure the data, this being left to
the Software Providers, which will continue to compete both within
and between market niches.
4. Just three levels of client engagement with the Health Sector are
envisaged: The ‘Encounter’, the ‘Episode of Care’, the ‘Disease
Course.’
Agreement about this data model would then permit further agreement on
conventions governing encryption, transmission, security etc. which
must be in place before a National System comes into use. An agreed
minimal structure as outline above is a prerequisite for such a viable
National system.
M. W. Mair
POB 319 Timaru
eyetech@es.co.nz
Monday, December 22, 1997