| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 681 |
| US National Library of Medicine maintained | 3461 |
| Uruguay extension module | 14 |
| Canada Health Infoway English | 73 |
| SNOMED CT Sweden NRC maintained | 548 |
| Danish | 24 |
| SNOMED Clinical Terms Australian extension | 74 |
| SNOMED CT United Kingdom clinical extension | 8586 |
Introduction
In January 2017, the Content Managers Advisory Group (CMAG) initiated an action to conduct a survey of the national extensions that were available, to date there has been limited information available - to other members and presumably SNOMED International. The responses of this survey are available here. The results shows a variety of extensions are produced, ranging from subset/refset, language translations and clinical content development. Subsequent activities investigating collaboration on subset may be pursued, but the CMAG was also interested in exactly what clinical content was in each extension, and how this might be shared. There should be very little clinical content that is exclusive to any country, and if it has been developed by one extension - it's likely globally relevant, and sharing it can reduce duplicated effort and maintenance burden of extension builders.
The results described here are a result of a combination of objective metrics (size of content), crude identifiction of duplicated effort, and finally some incidental quality observations. Further analysis of the content is still underway using description logic techniques, the results of which will be made available separately, at a later date.
SQL snippets are included in the document for future reference by author, but will unlikely be useful to public readership.
A summary of the results is available in the conclusion section at the end of this paper.
The cooperation of all Members is appreciated, and whilst all effort has been made to represent the extensions accurately, any inaccuracies are accidental.
Summary of Extensions
14 NRC responded to the survey, with 9 indicating they created clinical content extensions.
The Australian Edition also includes it's national drug extension, which has been excluded from this round of analysis (as no other extension appeared to include such content)
All extensions were based upon the July 2016 international release except one. This exception may produce some anomalies, but they are limited to the extension.
A raw analysis of the active concepts within an extension.
Note: UK extension (~30 thousand concepts) is about 6 times larger than US (5000) and has been excluded from the graph as an outlier. Raw values are shown to the right.
| NRC | Size | Primitive | Defined | ||
|---|---|---|---|---|---|
| AU | 1339 | 1056 | 78.9% | 283 | 21.1% |
| CA | 2040 | 2030 | 99.5% | 10 | 0.5% |
| DK | 290 | 290 | 100.0% | 0 | 0.0% |
| LT | 0 | 0 | N/A | 0 | N/A |
| NL | 1041 | 686 | 65.9% | 355 | 34.1% |
| SE | 1175 | 1060 | 90.2% | 115 | 9.8% |
| UK | 29793 | 29793 | 100.0% | 0 | 0.0% |
| US | 5100 | 2764 | 54.2% | 2336 | 45.8% |
| UY | 415 | 371 | 89.4% | 44 | 10.6% |
Ratio of active to inactive concepts
NRC | Proportion currently active |
|---|---|
| SNOMED CT Netherlands NRC maintained module | 95.3% |
| US National Library of Medicine maintained module | 93.3% |
| módulo de la extensión de Uruguay | 95.6% |
| Canada Health Infoway English module | 68.3% |
| SNOMED CT Sweden NRC maintained module | 99.6% |
| Australian common model component extension | 33.3% |
| Danish module | 88.4% |
| SNOMED Clinical Terms Australian extension | 97.0% |
| SNOMED CT United Kingdom clinical extension module | 32.9% |
All analysis was only performed on active content.
Extension changes against International Concept IDs
A total of 40 core concepts have been modified by extensions in some way.
Two were retired by an extension
- 384612007|pT4a: Tumor directly invades other organs or structures (colon/rectum) (finding)|
- 384613002|pT4b: Tumor penetrates visceral peritoneum (colon/rectum) (finding)|
- (A third concept was retired, but later reactivated)
One concept had a change to definition status (marked Defined) by an extension
- 399733007|Excision of retroperitoneal lymph node (procedure)|
Eight of these appear to be an attempt to address issues within the module assignment in the international release. (i.e. Concept inactivated on a different module to what they were created. metadata vs core).
The remainder are simply changes to moduleId, and either represent content promotion from an extension to the International. Or a possible error.
Extension Concepts
There appears to be around 52 unique semantic tags across the extension content. many of these are attributable to translations. Not all extensions provide english FSNs for extension content1, semantic tags were manually translated and merged.
After normalisation, this comes to 32 semantic tags. The distribution of content is shown below.
| Semantic Tag | Count |
| procedure | 11372 |
| finding | 6925 |
| observable entity | 5609 |
| disorder | 4783 |
| situation | 2677 |
| event | 2251 |
| qualifier value | 1903 |
| record artifact | 1361 |
| regime/therapy | 846 |
| assessment scale | 549 |
| occupation | 543 |
| substance | 503 |
| foundation metadata concept | 414 |
| morphologic abnormality | 321 |
| product | 320 |
| person | 134 |
| navigational concept | 132 |
| environment / location | 114 |
| organism | 114 |
| body structure | 106 |
| specimen | 95 |
| administrative | 66 |
| physical object | 59 |
| link assertion | 22 |
| core metadata concept | 19 |
| ethnic group | 16 |
| attribute | 7 |
| social concept | 5 |
| religion/philosophy | 4 |
| linkage concept | 3 |
| tumor staging | 2 |
| cell | 1 |
9 Modules are in use across the extensions.
ModuleId | FSN | Country |
|---|---|---|
| 11000146104 | SNOMED CT Netherlands NRC maintained module | NL |
| 731000124108 | US National Library of Medicine maintained module | US |
| 5631000179106 | módulo de la extensión de Uruguay | UY |
| 20621000087109 | Canada Health Infoway English module | CA |
| 45991000052106 | SNOMED CT Sweden NRC maintained module | SE |
| 161771000036108 | Australian common model component extension | AU |
| 554471000005108 | Danish module | DK |
| 32506021000036107 | SNOMED Clinical Terms Australian extension | AU |
| 999000011000000103 | SNOMED CT United Kingdom clinical extension module | UK |
The type of content by hierarchy
Each Top level hierarchy reviewed below for extension content.
Duplicates were found by comparing terms across extensions within given hierarchy. For example, "Look for duplicate terms within the procedure hierarchy". Duplicates within a module were also ignored.
Analysis was done on the complete aggregate of extensions plus the (International Core).
The presence of duplication may indicate:
- Extension concepts also in the core, either before or after.
- Those where the concept appears in the International release after it's creation in an extension represent a maintenance burden for NRC's in the absence of a promotion process.
- At least two countries producing similar, if not same, content. Which would suggest it's not necessarily country specific content.
Initial analysis is agnostic of description types, however analysis was further performed on just FSNs to increase likelihood of duplicate detection.
A major limitation in the approach used is that translations will (almost) be inherently unique, so comparison is dependent on English terms.
It was discovered mid analysis that a setting within the analysis database, may have caused incorrect character renderings however, this is not expected to have consequence on this analysis.
Clinical finding
Potential Concept Duplication
26 FSNs duplicated across the content, which are almost certainly candidates for promotion.
The affected concepts are in the following extensions.
- US National Library of Medicine maintained module
- SNOMED CT United Kingdom clinical extension module
- SNOMED CT Netherlands NRC maintained module
- SNOMED Clinical Terms Australian extension
- SNOMED CT Sweden NRC maintained module
- Danish module
All but the Danish module have some overlap with each other, as well as the international release.
These are the identified FSNs.
| Adverse reaction to rotavirus vaccine (disorder) | Atypical atrial flutter (disorder) |
| Chronic epiglottitis (disorder) | Excessive bioactive substance intake (finding) |
| Excessive enteral nutrition infusion (finding) | Excessive growth rate (finding) |
| Excessive parenteral nutrition infusion (finding) | Family history of lactose intolerance (situation) |
| Inadequate bioactive substance intake (finding) | Inadequate enteral nutrition infusion (finding) |
| Inadequate parenteral nutrition infusion (finding) | Mild dementia (disorder) |
| Patient identity verified (finding) | Physical disability (finding) |
| Predicted excessive energy intake (finding) | Predicted inadequate energy intake (finding) |
| Severe dementia (disorder) | Subendocardial myocardial infarction (disorder) |
| Suspected cerebrovascular accident (situation) | Suspected sepsis (situation) |
| Takotsubo cardiomyopathy (disorder) | Thrombosis of internal jugular vein (disorder) |
| Typical atrial flutter (disorder) | Unintentional weight gain (finding) |
| Ureterostomy present (finding) | Viral meningoencephalitis (disorder) |
For example:
- 371093006|Urosepsis (disorder)| has descriptions in, the extensions from three countries, that are the same as the 'en' descritpion.
- 27830001|Brachial radiculitis (disorder)| has translations in two extensions that are different to the 'en', but differ from eachother by the case of the first character.
- 75049004|Jeune thoracic dystrophy (disorder)| has translations in two extensions that appear identical.
These may have different character encoding or punctuation conventions, or written languages are genuinely similar (Danish and Swedish). A binary (eliminating case differences) compare halved the number of duplicate terms identified. It's unclear (to the author) what the standards and rules are concerning translations - are they complete (all concepts), some (only concepts of interest), as necessary (where word is different).
Procedure
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 43 |
| US National Library of Medicine maintained | 751 |
| Uruguay extension module | 176 |
| Canada Health Infoway English | 1214 |
| SNOMED CT Sweden NRC maintained | 483 |
| Danish | 1 |
| SNOMED Clinical Terms Australian extension | 960 |
| SNOMED CT United Kingdom clinical extension | 9732 |
Potential Concept Duplication
16 FSNs duplicated across the content, which are almost certainly candidates for promotion.
The affected concepts are in the following extensions.
SNOMED CT Netherlands NRC maintained module
US National Library of Medicine maintained module
SNOMED Clinical Terms Australian extension
SNOMED CT United Kingdom clinical extension module
Canada Health Infoway English module
SNOMED CT Sweden NRC maintained module
These are the identified FSNs.
| Admission to nursing home (procedure) |
| Alpha-1 microglobulin measurement (procedure) |
| Autopsy planned (situation) |
| Computed tomography of head, neck, abdomen and pelvis with contrast (procedure) |
| Decompressive craniectomy (procedure) |
| electrochemotherapy (procedure) |
| Flexible ureteroscopy (procedure) |
| Injection of platelet-rich plasma (procedure) |
| Laparoscopic extended right hemicolectomy (procedure) |
| Laparoscopic gastrectomy (procedure) |
| Laparoscopic radical prostatectomy (procedure) |
| Open reduction of fracture of ankle with internal fixation (procedure) |
| Open repair of strangulated incisional hernia (procedure) |
| Open repair of strangulated incisional hernia with prosthesis (procedure) |
| Rigid ureteroscopy (procedure) |
| Smoking assessment (procedure) |
Special concept
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 370 |
| US National Library of Medicine maintained | 1823 |
| Uruguay extension module | 59 |
| Canada Health Infoway English | 374 |
| SNOMED CT Sweden NRC maintained | 254 |
| Danish | 53 |
| SNOMED Clinical Terms Australian extension | 308 |
| SNOMED CT United Kingdom clinical extension | 4379 |
Potential Concept Duplication
15 FSNs duplicated across the content, which are almost certainly candidates for promotion.
The affected concepts are in the following extensions.
- SNOMED CT Netherlands NRC maintained module
- US National Library of Medicine maintained module
- SNOMED CT United Kingdom clinical extension module
- Canada Health Infoway English module
- SNOMED CT core module
- Danish module
- SNOMED Clinical Terms Australian extension
These are the identified FSNs.
| 5-Hydroxyhistamine (substance) |
| Atypical atrial flutter (disorder) |
| Autopsy planned (situation) |
| Birch pollen (substance) |
| Decompressive craniectomy (procedure) |
| Deer dander (substance) |
| Escherichia coli serogroup Orough (organism) |
| Highlands j virus (organism) |
| No diabetic retinopathy (situation) |
| Subendocardial myocardial infarction (disorder) |
| Suspected cerebrovascular accident (situation) |
| Suspected sepsis (situation) |
| Takotsubo cardiomyopathy (disorder) |
| Thrombosis of internal jugular vein (disorder) |
| Typical atrial flutter (disorder) |
Situation with explicit context
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 71 |
| US National Library of Medicine maintained | 340 |
| Uruguay extension module | 52 |
| Canada Health Infoway English | 376 |
| SNOMED CT Sweden NRC maintained | 194 |
| SNOMED Clinical Terms Australian extension | 114 |
| SNOMED CT United Kingdom clinical extension | 2877 |
Potential Concept Duplication
8 FSNs duplicated across the content, which are almost certainly candidates for promotion.
The affected concepts are in the following extensions.
- SNOMED CT United Kingdom clinical extension module
- SNOMED CT Netherlands NRC maintained module
- SNOMED CT Sweden NRC maintained module
- US National Library of Medicine maintained module
These are the identified FSNs.
| Autopsy planned (situation) |
| Family history of lactose intolerance (situation) |
| History of acute coronary syndrome (situation) |
| History of amaurosis fugax (situation) |
| History of supraventricular tachycardia (situation) |
| No diabetic retinopathy (situation) |
| Suspected cerebrovascular accident (situation) |
| Suspected sepsis (situation) |
Observable entity
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 20 |
| US National Library of Medicine maintained | 28 |
| Uruguay extension module | 26 |
| Canada Health Infoway English | 3 |
| SNOMED CT Sweden NRC maintained | 62 |
| Danish | 11 |
| SNOMED Clinical Terms Australian extension | 4 |
| SNOMED CT United Kingdom clinical extension | 5538 |
Potential Concept Duplication
There are no FSNs duplicated across the content.
There are 476 duplicate synonyms across this set. The affected concepts are in the following extensions.
- SNOMED CT Netherlands NRC maintained module
- SNOMED CT core module
- Danish module
- SNOMED CT Sweden NRC maintained module
- SNOMED CT United Kingdom clinical extension module
Event
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 2 |
| US National Library of Medicine maintained | 15 |
| Uruguay extension module | 1 |
| Danish | 1 |
| SNOMED CT United Kingdom clinical extension | 2230 |
Potential Concept Duplication
No FSNs are duplicated across the content.
17 synonyms are duplicated, the affected concepts are in the following extensions.
- Danish module
- SNOMED CT core module
- SNOMED CT Sweden NRC maintained module
- SNOMED CT Netherlands NRC maintained module
Qualifier value
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 100 |
| US National Library of Medicine maintained | 217 |
| Uruguay extension module | 104 |
| Canada Health Infoway English | 396 |
| SNOMED CT Sweden NRC maintained | 4 |
| Danish | 132 |
| SNOMED Clinical Terms Australian extension | 86 |
| SNOMED CT United Kingdom clinical extension | 2001 |
Potential Concept Duplication
28 FSNs duplicated across the content, which are almost certainly candidates for promotion.
The affected concepts are in the following extensions.
- SNOMED CT United Kingdom clinical extension module
- Canada Health Infoway English module
- US National Library of Medicine maintained module
These are the identified FSNs.
| Adolescent medicine service (qualifier value) | Adolescent psychiatry service (qualifier value) |
| Audiometry (qualifier value) | Cardiology service (qualifier value) |
| Chiropody (qualifier value) | Clinical allergy service (qualifier value) |
| Clinical genetics service (qualifier value) | Clinical immunology service (qualifier value) |
| Clinical neurophysiology service (qualifier value) | Dental hygiene service (qualifier value) |
| Dentistry service (qualifier value) | Dialysis service (qualifier value) |
| Endodontic service (qualifier value) | Genetics (qualifier value) |
| Health belief model (qualifier value) | Infectious diseases service (qualifier value) |
| Intensive care medicine (qualifier value) | Neonatal intensive care service (qualifier value) |
| Nephrology service (qualifier value) | Neurology service (qualifier value) |
| Physiotherapy service (qualifier value) | Prosthetics (qualifier value) |
| Prosthetics service (qualifier value) | Prosthodontic service (qualifier value) |
| Psychology (qualifier value) | Respiratory medicine service (qualifier value) |
| Respite care service (qualifier value) | Sports medicine (qualifier value) |
Record artifact
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 202 |
| US National Library of Medicine maintained | 4 |
| Uruguay extension module | 57 |
| SNOMED CT Sweden NRC maintained | 1 |
| SNOMED CT United Kingdom clinical extension | 1078 |
Potential Concept Duplication
8 FSNs duplicated across the content, which are almost certainly candidates for promotion.
The affected concepts are in the following extensions.
- SNOMED CT Netherlands NRC maintained module
- SNOMED CT United Kingdom clinical extension module
These are the identified FSNs.
| Discharge letter (record artifact) |
| Do not attempt cardiopulmonary resuscitation order (record artifact) |
| Growth chart (record artifact) |
| Letter (record artifact) |
| Living will and advance directive record (record artifact) |
| Medical photograph (record artifact) |
| Referral letter (record artifact) |
| Weight chart (record artifact) |
Social context
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 5 |
| US National Library of Medicine maintained | 41 |
| Uruguay extension module | 56 |
| Canada Health Infoway English | 56 |
| SNOMED CT Sweden NRC maintained | 3 |
| Danish | 21 |
| SNOMED Clinical Terms Australian extension | 6 |
| SNOMED CT United Kingdom clinical extension | 603 |
Potential Concept Duplication
5 FSNs duplicated across the content, which are almost certainly candidates for promotion.
The affected concepts are in the following extensions.
- US National Library of Medicine maintained module
- SNOMED Clinical Terms Australian extension
- Canada Health Infoway English module
These are the identified FSNs.
| Massage therapist (occupation) |
| Maternal aunt (person) |
| Maternal uncle (person) |
| Paternal aunt (person) |
| Paternal uncle (person) |
Substance
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 4 |
| US National Library of Medicine maintained | 418 |
| Canada Health Infoway English | 292 |
| SNOMED CT Sweden NRC maintained | 3 |
| Danish | 166 |
| SNOMED Clinical Terms Australian extension | 60 |
| SNOMED CT United Kingdom clinical extension | 20 |
Potential Concept Duplication
15 FSNs duplicated across the content, which are almost certainly candidates for promotion.
The affected concepts are in the following extensions.
- US National Library of Medicine maintained module
- SNOMED Clinical Terms Australian extension
- Canada Health Infoway English module
- SNOMED CT core module
- SNOMED CT United Kingdom clinical extension module
These are the identified FSNs.
| 5-Hydroxyhistamine (substance) |
| Arugula (substance) |
| Birch pollen (substance) |
| Blue cheese (substance) |
| Deer dander (substance) |
| Flounder (substance) |
| Ham (substance) |
| Hickory nut (substance) |
| Honeydew melon (substance) |
| Jalapeno pepper (substance) |
| Pneumococcal conjugate vaccine (product) |
| Red onion (substance) |
| Snail - dietary (substance) |
| Tree nut (substance) |
| White pepper (substance) |
Body structure
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 1 |
| US National Library of Medicine maintained | 21 |
| Uruguay extension module | 1 |
| Canada Health Infoway English | 4 |
| SNOMED CT Sweden NRC maintained | 2 |
| Danish | 4 |
| SNOMED Clinical Terms Australian extension | 2 |
| SNOMED CT United Kingdom clinical extension | 393 |
Potential Concept Duplication
No FSNs duplicated across the content.
1,888 synonyms are duplicated across the content, the affected concepts are in the following extensions.
- Danish module
- SNOMED CT Sweden NRC maintained module
- SNOMED CT core module
- Lithuania
- SNOMED Clinical Terms Australian extension
- US National Library of Medicine maintained module
- SNOMED CT United Kingdom clinical extension module
Staging and scales
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 1 |
| US National Library of Medicine maintained | 5 |
| SNOMED CT Sweden NRC maintained | 12 |
| Danish | 1 |
| SNOMED Clinical Terms Australian extension | 2 |
| SNOMED CT United Kingdom clinical extension | 535 |
Potential Concept Duplication
No FSNs duplicated across the content, which are almost certainly candidates for promotion.
464 synonyms are duplicated across the extensions. The affected concepts are in the following extensions.
- Danish module
- SNOMED CT core module
- SNOMED CT Sweden NRC maintained module
- SNOMED CT United Kingdom clinical extension module
Pharmaceutical / biologic product
| NRC | Concepts |
| US National Library of Medicine maintained | 263 |
| Canada Health Infoway English | 240 |
| Danish | 141 |
| SNOMED Clinical Terms Australian extension | 30 |
| SNOMED CT United Kingdom clinical extension | 47 |
Potential Concept Duplication
12 FSNs duplicated across the content, which are almost certainly candidates for promotion.
The affected concepts are in the following extensions.
- Canada Health Infoway English module
- US National Library of Medicine maintained module
- SNOMED Clinical Terms Australian extension
These are the identified FSNs.
| Arugula (substance) |
| Blue cheese (substance) |
| Flounder (substance) |
| Ham (substance) |
| Hickory nut (substance) |
| Honeydew melon (substance) |
| Jalapeno pepper (substance) |
| Pneumococcal conjugate vaccine (product) |
| Red onion (substance) |
| Snail - dietary (substance) |
| Tree nut (substance) |
| White pepper (substance) |
Organism
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 73 |
| US National Library of Medicine maintained | 24 |
| SNOMED CT Sweden NRC maintained | 1 |
| Danish | 12 |
| SNOMED Clinical Terms Australian extension | 1 |
| SNOMED CT United Kingdom clinical extension | 3 |
Potential Concept Duplication
2 FSNs duplicated across the content, which are almost certainly candidates for promotion.
The affected concepts are in the following extensions.
- US National Library of Medicine maintained module
- SNOMED CT core module
- Canada Health Infoway English module
These are the identified FSNs.
| Escherichia coli serogroup Orough (organism) |
| Highlands j virus (organism) |
Environment or geographical location
| NRC | Concepts |
| US National Library of Medicine maintained | 11 |
| Canada Health Infoway English | 4 |
| Danish | 41 |
| SNOMED CT United Kingdom clinical extension | 81 |
Potential Concept Duplication
No FSNs duplicated across the content.
353 synonyms are duplicated across the extensions, The affected concepts are in the following extensions.
- Danish module
- SNOMED CT Sweden NRC maintained module
- SNOMED CT core module
- Lithuania
Specimen
| NRC | Concepts |
| US National Library of Medicine maintained | 38 |
| SNOMED CT United Kingdom clinical extension | 56 |
Potential Concept Duplication
No FSNs duplicated across the content.
Nine synonyms are duplicated. The affected concepts are in the following extensions.
- Danish module
- SNOMED CT Sweden NRC maintained module
- SNOMED CT core module
- US National Library of Medicine maintained module
- SNOMED CT United Kingdom clinical extension module
Physical object
| NRC | Concepts |
| SNOMED CT Netherlands NRC maintained | 5 |
| US National Library of Medicine maintained | 33 |
| SNOMED CT Sweden NRC maintained | 1 |
| SNOMED CT United Kingdom clinical extension | 20 |
Potential Concept Duplication
No FSNs duplicated across the conten.
399 synonyms are duplicated across the extensions. The affected concepts are in the following extensions.
- Danish module
- SNOMED CT Sweden NRC maintained module
- SNOMED CT core module
Physical force
Single Concept : U-V radiation in diagnosis NOS (physical force)
Extension Descriptions
Most analysis performed as part of identifying duplicates within concepts. However, below is a summary of the translations - (extension descriptions for core concepts).
| NRC | Translated Concepts |
| SNOMED CT Netherlands NRC maintained module | 6759 |
| US National Library of Medicine maintained module | 169 |
| Uruguay extension module | 227 |
| Canada Health Infoway French module | 34063 |
| Canada Health Infoway English module | 533 |
| SNOMED CT Sweden NRC maintained module | 298331 |
| Danish module | 254752 |
| SNOMED Clinical Terms Australian extension | 1929 |
| Lithuania | 42668 |
| SNOMED CT United Kingdom clinical extension module | 3799 |
| Language | Concepts |
| da | 254752 |
| en | 6327 |
| es | 227 |
| fr | 34063 |
| lt | 42668 |
| nl | 6756 |
| sv | 298331 |
Extension Changes to Core Descriptions
178 International descriptions have some modification in an extension. The associated modules are:
- Australian common model component extension
- SNOMED Clinical Terms Australian extension
- US National Library of Medicine maintained module
Relationship Extensions
5,136 core concepts have been changes within an extension. Some of these look like promotions, however the majority do not appear to be.
| Extension | Inferred | Stated |
| Australian common model component extension (core metadata concept) | 4 | 57 |
| Canada Health Infoway English module (core metadata concept) | 40 | 0 |
| Danish module (core metadata concept) | 12 | 6 |
| Uruguay extension module (core metadata concept) | 62 | 23 |
| SNOMED Clinical Terms Australian extension (core metadata concept) | 357 | 98 |
| SNOMED CT Netherlands NRC maintained module (core metadata concept) | 688 | 0 |
| SNOMED CT Sweden NRC maintained module (core metadata concept) | 17 | 0 |
| SNOMED CT United Kingdom clinical extension module (core metadata concept) | 2862 | 2848 |
| US National Library of Medicine maintained module (core metadata concept) | 1125 | 401 |
Note: Some of the numbers comparing stated and inferred look odd, this is likely a result of the crude aggregation of extensions and some of the extension content already having been promoted to core.
Core relationships modified within an Extension
1,997 core relationships where modified by an extension, affecting 384 concepts
A single concept, 425630003|Acute irritant contact dermatitis (disorder)| was modified by two NRCs.
Both inactivated all the relationships, but one recreated them in the subsequent release.
Other changes are summarised below.
| NRC | Relationships Changed |
| SNOMED CT Netherlands NRC maintained module | 1570 |
| Uruguay extension module | 296 |
| Canada Health Infoway English module | 80 |
| SNOMED CT Sweden NRC maintained module | 16 |
| Australian common model component extension | 12 |
| Danish module | 8 |
| SNOMED Clinical Terms Australian extension | 15 |
Types of Relationships Modified
A large variety (43) of relationship types are involved in the edits, most are IS A, and some are not part of the approved concept model or are attributes specific to an extension.
| Relationship Type | Number of relationships |
| After | 12 |
| Associated finding | 69 |
| Associated morphology | 263 |
| Associated procedure | 50 |
| Associated with | 11 |
| Causative agent | 43 |
| Clinical course | 24 |
| Component | 1 |
| Direct device | 4 |
| Direct morphology | 17 |
| Direct substance | 1 |
| Due to | 24 |
| Finding context | 69 |
| Finding site | 331 |
| Has active ingredient | 3 |
| Has definitional manifestation | 17 |
| Has dose form | 2 |
| Has focus | 3 |
| Has intent | 11 |
| Has interpretation | 3 |
| Has specimen | 3 |
| Interprets | 27 |
| Is a | 2209 |
| Method | 90 |
| MOVED FROM | 32 |
| Occurrence | 94 |
| Pathological process | 37 |
| PBCL flag true | 2860 |
| Procedure context | 53 |
| Procedure site | 6 |
| Procedure site - Direct | 70 |
| Procedure site - Indirect | 3 |
| Route of administration | 1 |
| Severity | 7 |
| Specimen source identity | 1 |
| Specimen source topography | 1 |
| Specimen substance | 1 |
| Subject relationship context | 122 |
| Surgical approach | 1 |
| Temporal context | 122 |
| Using access device | 3 |
| Using device | 7 |
| Using substance | 6 |
Comparison Examples - Published (inferred) relationships for Core concepts
Concept | Core | Extension |
|---|---|---|
| 371040005 |
|
|
| 321000119108 |
|
Note: This example, appears to be a promoted concept. But the local relationships haven't been inactivated upon promotion. Examples such as this are a use case for promoting both stated and inferred relationships. Such that maintenance burden on NRCs is reduced, and authoring effort recognised. |
| 212385001 |
|
|
Additional Observations
The following observations are only exemplars of the observations made, and by no means comprehensive.
Extensions vs Editions
Of the 9 releases looked at:
- Four publish Editions
- Three publish Extensions
- One publishes three separate extensions.
- One publishes an extension, "bundled" with the International Edition.
File naming
The file naming conventions, do not appear to be consistent across the extensions.
- sct2_Concept_Snapshot_AU1000036_20161231.txt
- sct2_Concept_Snapshot_en-CanadianExtension_20161031.txt
- sct2_Concept_Snapshot_DK1000005_20161130.txt
- sct2_Concept_Snapshot_LT1000092_20151107.txt
- sct2_Concept_Snapshot_NL_20160930.txt
- sct2_Concept_Snapshot_SE1000052_20161130.txt
- sct2_Concept_Snapshot_GB1000000_20161001.txt
- sct2_Concept_Snapshot_US1000124_20160901.txt
- sct2_Concept_Snapshot_es-UruguayExtension_20161215.txt
- sct2_Concept_Snapshot_INT_20160731.txt
Directory structure
Some variation was noticed in the the directory structure within the published zip files.
Below are the paths the the snapshot concepts file in each release.
- \SnomedCT_Release_AU1000036_20161231\RF2Release\Snapshot\Terminology
- \SnomedCT_Canadian_EnglishExtension_Release_20161031\Snapshot\Terminology
- \SnomedCT_ManagedServiceDK_Production_DK1000005_20161130\Snapshot\Terminology
- \SnomedCT_RF2Release_LT1000092_20151107\Snapshot\Terminology
- \SnomedCT_Netherlands_EditionRelease_20160930\Snapshot\Terminology
- \SnomedCT_SE_Production_20161130T170000\Snapshot\Terminology
- \SnomedCT_RF2Release_GB1000000_20161001\Snapshot\Terminology
- \SnomedCT_RF2Release_US1000124_20160901\Snapshot\Terminology
- \SnomedCT_Uruguay_Extension_Release_20161215\Snapshot\Terminology
Specific file inclusions
The international release includes 6 files - Concepts, Description, Relationship,StatedRelationship,Identifier and TextDefinition files - within the "Terminology Folder"
The files are not consistently present in extensions.
Concept | Description | Relationship | StatedRelationship | Identifier | TextDefinition | |
|---|---|---|---|---|---|---|
| Australia | 1 | 1 | 1 | 1 | ||
| Candana* | 1 | 1 | 1 | 1 | 1 | |
| Denmark** | 1 | 2 | 1 | 1 | 1 | 2 |
| Lithuania | 1 | 1 | 1 | |||
| Netherlands | 1 | 1 | 1 | 1 | ||
| Sweden** | 1 | 2 | 1 | 1 | 1 | |
| UK | 1 | 1 | 1 | 1 | ||
| USA | 1 | 1 | 1 | 1 | 1 | 1 |
| Uruguay | 1 | 1 | 1 | 1 | 1 |
* Canada include a French and English bundle.
** Sweden and Denmark include both an English and Native language Description file.
Denmark and USA are the countries to include all 6 files.
Further variations are present within the refset subdirectories.
Miscellaneous QA issues
The description file for one extension for found to be missing the language code for 268 entries. (The country was notified and have rectified).
Conclusion
- The analysis described above is reveals a wealth of information. There is evidence of duplication of content in almost every hierarchy, the extent of which likely to be much greater given the primitive analysis techniques used.
- There is value to the whole SNOMED CT community to introduce a process for content to be promoted through to core. This process should honour the identifiers issued by an extension builder, so as to minimise maintenance burden of the originating extension, and recognising their effort. The current process is prohibitive to promoting content, and consequently content is duplicated across extensions, the potential maintenance debt grows.
- Almost all NRCs are actively modifying core content. Which proves the importance of clarifying the issues raised in the Discussion Paper - Allowance of Extensions to Modify Core Content (SNOMED International Response). It seems Members have taken a different interpretation of the license to that held by the governing body, and this discrepancy has never been recognised.
- Variations in the artefacts published by NRCs exist. No comment is made about compliance with Technical Specifications, but such variances may impact portability of software that consumes SNOMED CT. Some sort of certification/verification process asserting a minimum conformance criteria would prove valuable.
- All the issues described here may just as likely apply to other (affiliate) extensions, however will remain unknown without systematic investigation.
- The issues described are real and Members are currently struggling to deal with. Prolonging their resolution introduces a cost to all.
Endnotes
1The author recalls a requirement that a US spelling 'en' FSN should be created for all concepts, but unable to identify this in current specification. Is this still a requirement?
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