National Standard SNOMED CT
subset for Diagnostic Imaging
procedures and the relationship to
local 'Order Catalogues'
Ian Arrowsmith
NHS Connecting for Health
Royal College of Radiologists PACS and
Teleradiology Special Interest Group
20th April 2005
Structure of presentation
• The need for a National Standard
– The NHS Care Record Service ‘Spine’
• The National Subset of DI procedures
– Principles
• Relationship to local/cluster order
catalogues
• Management arrangements
The NHS Care Record Service
‘Vision’
• The “Continuity of Care Record”
– The NHS Care Record Spine is a universally
accessible (to those with an authority to view)
repository of Health Care information for every
person in England.
– The content of the record can be thought of as
the minimum information required by a clinician
when seeing a patient for the first time in the
absence of a referral from a clinical colleague.
That is not to say that the record will only be
used in unplanned and emergency situations.
The Spine – clinical events through time
Patient info
Patient info
LSP
Patient visits GP
Patient visits A&E
LSP
Broken Leg
Back Pain
Spine
Patient info
LSP
Patient visits hospital
Chest infection
The information flow is repeated over time
SNOMED CT
• All structured clinical information will be
represented in the NCRS using
SNOMED Clinical Terms® and will be
communicated to and from the Spine
using HL7 v3 messages
• It is therefore essential that Diagnostic
Imaging procedures are represented
effectively in SNOMED CT and that the
terminology is used consistently
throughout the NHS CRS
Subsets
• A SNOMED CT subset is a collection of
terminology, selected and grouped for a
particular purpose. A subset may be
composed of anything from a single
component to the entire set of concepts,
descriptions or relationships - and are
commonly needed for:
–
–
–
–
Data quality improvement
Message field validation
Simplified data entry and retrieval
Elimination of ‘noise’
The National SNOMED CT
Subset of DI procedures
• A comprehensive set of DI procedure
descriptions to ensure Nationally
consistent recording of all DI procedures
undertaken in the NHS using the
mandated terminology
• Expressed simply as the modality, the
body site and, where necessary, the
laterality (some notable exceptions)
Principles
• Descriptions should be clear and
unambiguous both within and
outside the DI business domain
• Descriptions should represent
clinical activity and not
administrative functions
Modalities
•
•
•
•
X-Ray (includes Mammography)
US scan (includes Obstetric ultrasound)
CT
MRI (includes Magnetic resonance
angiography)
• Radionuclide Study (includes single
photon emission computed tomography)
• Fluoroscopy (includes angiography)
• DEXA scan ?
Example descriptions and userfriendly alternatives
Arterial Stent Renal
Fluoroscopic angiography of renal
artery and insertion of stent
Right ventriculogram
Fluoroscopic angiography of right
cardiac ventricle
Hysterosalpingogram
Fluoroscopy of uterus and
fallopian tubes
Exceptions
•
•
•
•
Barium follow through
CT leg length measurement
High Resolution CT of lungs
Radionuclide gastric emptying study
– Plus many more Nuclear medicine
procedures
Current status
• Delivery end of this week
• Review by workshop attendees (2
weeks)
• Revision of list (1 week)
• Changes effected in SNOMED CT (?
by summer 2005)
• Formal release ( ? by autumn 2005)
Existing ‘order catalogues’
• Current situation
– Development of cluster-wide lists
• Including an RCR approved one
– Other local lists in service provider
departments
– GP systems (Read codes)
– National subset
Issues
•
•
•
•
•
•
There are very few systems which currently have the capability
of SNOMED CT encoding directly and it will be many years
before all systems enable this.
Some LSP’s, in conjunction with their sub-contractors and
local health communities have developed catalogues ahead of,
and therefore inconsistent with, the emergent nationally
agreed subset principles
Any new arrangements must not cause detriment to existing
information flows
Replacement Radiology systems are being procured to
support the roll-out of PACS which are not required to
integrate with the common NCRS architecture in the short
term.
Different levels of granularity/specificity are required at
different points in the requesting/reporting workflow.
Mapping automatically from a less detailed coding scheme to a
more detailed one is generally not considered acceptable
where the relationship is not a logical one-to-one map.
Whether receiving requests or reports, receiving systems
which cannot process incoming data are therefore expected to
deprecate the content to text unless there is a degree of
manual intervention.
Resolution
• With specific reference to the domains of DI
and pathology it has been decided that NPfIT
will allow mapping between the local code lists
and the National Standard subsets for
population of the relevant fields in the NPfIT
HL7v3 messages.
• In the requesting systems however, the local
term instances will be exact lexical equivalents
to descriptions in the national Standard Subset
so although a translation will occur (from READ
to SNOMED CT) this will be a one-to-one
relationship.
For requesting in an inter-organisational
environment and for populating messages
• Requesters will only be allowed to order from the list of
descriptions in the National Standard list (even though
they may be represented in a different coding scheme
eg Read codes).
• These descriptions will be lexically equivalent where
possible with the items in the National subset. Where
this is not possible (due to term length constraints for
instance) then the local description must have a
mapping to a single entry in the National subset.
• On receipt of the request by the service provider system,
business rules may be utilised to translate the
procedure/investigation from the National standard list to
the local equivalent or it may simply be deprecated to
text.
• Responsibility for the accuracy of this process and the
creation of any mapping tables lies with the local health
community representatives in conjunction with the
system supplier
For reporting in an inter-organisational
environment and for populating messages
•
•
In service provider systems, where a concept does not
exist in the National list, the local form should be
mapped to the closest approximation from the list with
any additional clinically significant information
provided in the original text/code fields in the report
message. This is only permitted in the case of
outgoing communication from service providers.
On eventual receipt of the report, the original
requesting system may utilise business rules to
translate the result or it may simply be deprecated to
(structured) text. Responsibility for the accuracy of this
process and the creation of any mapping tables lies
with the local health community representatives in
conjunction with the system supplier.
For reporting in an inter-organisational
environment and for populating messages
• The system supplier will provide evidence that any mapping
tables utilised for mapping from service provider
descriptions to the National subset (for outgoing messages)
or to the National subset from local descriptions (for
incoming messages) are technically robust as part of the
accreditation process
• On creation of the result within the diagnostic service
provider system, the local coding instance will be mapped
to the NPfIT mandated representation for communication to
requester and PSIS
• Interactions within the Local Service Provider environment,
i.e. internal Order Comms between Hospital departments,
may utilise the local code and local textual description
Example - requesting
• Patient is complaining of knee pain and GP believes this
may be due to arthritic changes and requests a ‘left knee
X-ray’. GP enters search string which returns a
selection of national catalogue post co-ordinated
expression for direct selection, i.e. is coding using
SNOMED CT and national catalogue eg Left knee X-ray
• The GP validates the message content and sends the
request message via TMS to service provider
• The message is received at service provider system and
is mapped according to locally designed business rules
or by manual entry to the local order catalogue entry to
the term ‘Left knee X-ray – osteoarthritis protocol’ (local
code = 0003)
Example - reporting
• Patient attends, examination is performed and
subsequently reported and the report message
is sent to PSIS and to the requester.
• The entry for ‘Left knee X-ray – osteoarthritis
protocol’ is translated through the use of locally
created mapping tables to the equivalent
National standard list entry which in this case is
Left knee X-ray for population of the message
• The report message is received by the GP
system and the procedure item is either
rendered on the screen (and subsequently
manually coded) or processed by the system
and translated back into the Read code/term
Migration guidance
• The catalogues should be adopted over as many
organisations and as wide a geographical area as
possible
• Where possible, real descriptions from SNOMED CT
should be incorporated in the local order catalogue (not
necessarily the preferred term)
• With particular respect to DI, it is recommended that the
Radiology Descriptors and short codes catalogue that
has been developed after wide consultation, and has
been approved by the Royal College of Radiologists, be
adopted for all existing and new non-SNOMED CT
enabled NPfIT Cluster RIS systems - these are in the
process of being mapped to the National Standard list
• A professionally led, responsive management
mechanism for the national catalogues will be
established
Further information
http://www.connectingforhealth.nhs.uk/
technical/standards/