The Vocabulary browser provides a simple structured way to browse the Cochrane vocabulary and see how the terminology is being used.
What the Vocabulary browser provides | ||
|---|---|---|
| 1 | Number of systematic reviews which have been annotated with the terms in the vocabulary |
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| 2 | Vocabularies from where the term has been taken | |
| 3 | The parent or broader terms | |
| 4 | The child or narrower terms | |
Controlled vocabularies used to build the Cochrane vocabulary
The Linked Data team chose controlled vocabularies to build the Cochrane vocabulary with the following aims:
- Acceptable for use across Cochrane
- Structured in a way that allows them to be linked to other parts of the linked data universe
- Compatible with vocabularies already in use within Cochrane or by our close collaborators.
| Controlled vocabularies | |
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MedDRA | |
WHO ATC/DDD |
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RxNorm |
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SNOMED CT |
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Which vocabularies are relevant to P, I, C, or O?
Vocabularies for P
For age and sex, MeSH ranges and headings are used.
Terms for the Condition portion of P are drawn from two standard vocabularies - MedDRA and SNOMED CT. All of the terms from MedDRA are available for P annotation, but only selected subsets of SNOMED have been included.
Vocabularies for I and C
The terms for drug interventions come from the following vocabularies:
- RxNorm
- WHO ATC
- SNOMED CT
Drug categories
WHO ATC and SNOMED CT are used for drug categories.
Many interventions (especially at the review level) are drug categories rather than a single agent - antibiotics, vitamins, analgesics, etc. RxNorm only lists individual drugs or drug combinations and has no codes for drug categories.
Individual drugs
Since both RxNorm and WHO ATC have terms for individual drugs, either one can be used to annotate a drug intervention. However, the terms in WHO ATC are linked to drug categories while the terms in RxNorm are not. Because of this, a drug with multiple uses may appear more than once in different parts of the WHO ATC vocabulary tree.
In cases where there are several options to choose from, for instance one or more WHO ATC codes and an RXNorm code, then it is best to use the most appropriate WHO ATC codes rather than the RxNorm code.
If you are not sure which one to choose, use the RxNorm code.
Drug combinations
Non-drug interventions
Terms for all non-drug interventions are drawn from SNOMED CT. As with P, only selected subsets of this vocabulary are included in the Cochrane vocabulary.
If you find a term in SNOMED that would be applicable for annotation of a non-drug intervention, but you cannot access the term in the I or C part of the PICO annotator, please request it via the Vocabulary Request form on your Review Group page.
Vocabularies for O
Many of the terms used in the Conditions section of P are also applicable to outcomes. Therefore, the same controlled vocabulary terms that are available in P (MedDRA and portions of SNOMED CT) are used for Outcomes.
Synonyms and near synonyms in the controlled vocabularies
When synonyms or near-synonyms appear in the controlled vocabularies, then the following processes will be followed to standardize annotations.
There is now a type-ahead function in the PICO annotator that shows the frequency of term use (i.e. the number of times a term has been used by annotators is displayed immediately after each term in the drop-down menu for each PICO component).
A term in one vocabulary has a synonymous term in the same vocabulary
MedDRA
MedDRA has been structured so that every term at the second-lowest level of its hierarchy (PT - Preferred Term) has a synonymous term at its lowest level (LLT - Lowest Level Term). The LLT member of each of these pairs has been removed from the Cochrane vocabulary, so there should be no exactly identical terms from MedDRA. If you uncover any examples in the course of annotation or QA, please send a Merge request via the Vocabulary Request form on your Review Group page. However, there may be other close matches within MedDRA; for example, UK and US spellings of a term (oedema, edema etc.) are separate terms in MedDRA. This will be resolved in a way that will merge these MedDRA synonyms.
Interim work-around
- If one of the MedDRA synonyms is linked to a SNOMED term, pick that one.
- Annotate using the more frequently used term. If needed, send a Preferred Term Selection request via the Vocabulary Request form on your Review Group page.
- If a UK spelling exists, please use it. If you do find US spellings, request a Merge of these terms via the Vocabulary Request form on your Review Group page.
WHO ATC
Duplication arising from different formulations of the same drug
WHO ATC is organized by organ system, so a drug that is used in different formulation for different body systems will have multiple entries in the original WHO vocabulary (e.g. tetracycline formulations for application to the skin have a term that starts with D (dermatologic), those for use in eyes or ears have an S (sensory), in the mouth it's A (alimentary) etc.) The Linked Data team has merged all of these terms into a single Cochrane tetracycline term and merged it with related terms from RxNorm and SNOMED CT - so tetracylcline is now mapped to
SNOMED: 66261008
RxNorm: 10395
ATC: S02AA08,S03AA02,S01AA09,J01AA07,D06AA04,A01AB13
MeSH: D013752
Duplication in Drug Category arising from different formulations of the same drug
The WHO drug categories are organised by organ system, and WHO has chosen to give identical labels or labels that appear synonymous to drug categories in different (organ system) parts of their vocabulary.
The parent terms for Tetracycline include Tetracyclines, Antiinfectives, Antibiotics, and a second Antiinfectives and these categories are based on organ systems. The two Antiinfective terms, for example, apply to tetracycline eye or ear drops, so would not be an appropriate choice for an annotation of systemic anti-infectives. The LInked Data team is working to relabel the WHO drug categories to make these distinctions clearer, but if there are apparent synonyms, the correct term can be chosen by looking at the initial letter in the WHO identifier.
Duplication due to multiple uses of the same (or similar) terms at different levels in the WHO-ATC hierarchy
ATC has 3 closely related terms - Tetracyclines J01A, Tetracyclines J01AA, and Tetracycline J01AA07. These are actually 3 different levels in the hierarchy:
Tetracyclines J01A
Tetracyclines J01AA (and this is the only child term under Tetracyclines J01A
Tetracycline J01AA07.
The duplication of the Tetracyclines label for J01A and J01AA, with J01AA being the only child happens elsewhere within ATC as well. (e.g. Antimycotics for systemic use J02/Antimycotics for systemic use J02A).
The Tetracyclines/Tetracycline duplication is somewhat different. Tetracycline is a specific drug and one of several members of the class Tetracyclines, so the 2 terms are not equivalent or interchangeable. This situation should be fairly rare (Tetracycline(s) may be the only example).
A term in one vocabulary has a synonymous term in a different vocabulary
MedDRA and SNOMED CT
The Linked Data team has attempted to identify all cases in which a term in MedDRA has a label that is identical to the label from a term in SNOMED CT and these have been merged into a single Cochrane term - with both parent terms listed in the the various tools whenever the term is used.
In addition to these exact synonyms, there are many cases in which a term in MedDRA looks as if it is probably identical to a term in SNOMED CT but has a slightly different label. An example is the MedDRA term Premature Baby & the SNOMED CT term Premature Infant. These have now been combined into a single Cochrane term with the label Preterm Infant (Less than 37 weeks).
