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- Navigate this page:
- SNOMED ID Codes (sctids)
- Where to begin The prescribing_term_index and the charting_term_index
- What is a Prescribing Term
- What is a Charting Term
- Prescribing and Charting Terms – a comparison example
- Variations in the Indexes
- Prescribing and Charting Terms – a pack level example
The NZMT Data ModelThe New Zealand Medicines Terminology (NZMT) database has been designed from the SNOMED design model, and is intended to provide a single, consistent database of names for medicines and trade products containing these medicines. The NZMT logical data model is very similar to that of the Australian Medicines Terminology (AMT) even though the physical data models are very different. OverviewThe SNOMED design model means that almost all the tables have an id column (unique within the NZMT), a PreferredTerm column and a FullySpecifiedName column. Most reference tables have only these three columns, while the main concept tables (CTPP, TP, TPP, TPUU, MP, MPP, MPUU) have a number of other columns. Tables that are an addition to the original SNOMED model such as nzmt_atc_links do not necessarily conform to this design model. Section 6 of this document contains examples of the PreferredTerms of the main concept tables, and full technical details of all tables can be found in the Data Overview document included in the NZULM download. SNOMED ID Codes (sctids)OverviewThe SNOMED specification requires that all records are identified by a globally unique 18-digit number. This means that you can create a single lookup table inside your database that contains all the id numbers of all the NZMT records in your database and you won’t get a single duplicate. The primary purpose of this globally unique key is to allow records from any of the Medicines Terminologies operated by SNOMED member nations to co-exist in a single database if required.
Data FormatId numbers that are 18 digits wide are just slightly too large to fit within the largest integers supported by most databases, so all record IDs are stored as 18 character strings. Important Note: When importing .csv files containing these fields into Excel you need to specify the fields as ‘text’. If you don’t Excel will recognise them as numeric but will not have a sufficiently large numeric field to enter them into and so truncate them. The truncation is somewhat insidious as all 18 digits will be displayed but the right-hand-most digit will be 0. As this is the checkdigit it is normally not 0. Key StructureThe 18-digit key contains (in order): an 8-digit sequence number a 7 digit national “namespace” number (1000117 or 1000116 for the NZMT) a 2 digit SNOMED “type” code known as the ‘partition code’ a single checkdigit E.g.: 50004811000117106 breaks down as: 5000481 – 1000117 – 10 – 6 Please note: The Australian national namespace code is: 1000036. You can use this to identify data imported from the Australian Medicines Terminology (AMT). We currently only use 7 of the available 8 digits in the initial sequence number, so as in our example above almost all of our sctids are actually 17-character strings. The SNOMED ‘partition code’ has three values: 10 for Concept IDs, 11 for Description IDs and 12 for Relationship IDs. The example above is therefore a Concept ID and is actually the sctid for a CTPP record. All of the seven primary tables and of the lookup tables are considered to have Concept IDs. The descriptions table has Description IDs, while relationship tables such as MHM and THT have Relationship IDs. The “Seven Box” ModelThe NZMT contains 7 primary concept tables designed to hold the seven distinct “product” concepts, each containing a set of logical data elements and each participating in a number of relationships with other concepts. Four of these (CTPP, TPP, TPUU and TP) are trade concepts and include brand name information, while the other three (MPP, MPUU and MP) are generic and do not contain brand name information. Supporting these primary tables are tables that define relationships between the primary tables or between the primary tables and the reference tables. There are a number of reference tables to hold reference data required by the primary tables. Finally, there is the descriptions table which holds descriptions for each of the primary concept tables – including PreferredTerms and FullySpecifiedNames as well as all the alternate terms available. 
Please note In this diagram the arrows indicate the route your SQL query will have to take to find any specific set of records if you start from the CTPP end of the structure and want to find the associated TP and MP records. The MHM and THT tables are shown here for completeness, but are relationship tables rather than concept tables. Where to begin?The prescribing_term_index and the charting_term_indexOur recommendation is that you use one of our two alternate term indexes, the prescribing_term_index or the charting_term_index as the starting point for exploring the NZULM. Both of these indexes have the same structure. The differences between the two indexes are the alternate terms that they provide. Both prescribing terms and charting terms are alternate terms for a given concept. Both of these indexes are intended to provide generic and trade terms for all the products listed in the NZULM. What is a Prescribing Term?Prescribing Terms are alternatives to concept PreferredTerms for use where the PreferredTerm may be too involved or lengthy. They were developed initially for use in primary sector prescribing systems and have a maximum length of 200 characters. What is a Charting Term?Charting Terms are also alternatives to concept PreferredTerms for use where the PreferredTerm may be too involved or lengthy. They were developed initially to meet the requirements of hospital charting systems and have a maximum length of 160 characters. What’s the difference?These two terms are often very similar. The significant difference, other than length, is found in the trade terms. The trade charting term does not include details of the generic medicines in the product, whereas the trade prescribing term does. Prescribing and Charting Terms – a comparison example
In this example showing the prescribing_term_index and charting_term_index for the same product, you can see that the generic terms are identical. The two trade terms are different, however, and so the trade_description_ids are different. This particular product has its active ingredients listed in the sequence that the manufacturer uses on the product’s packaging. This is a variation to the standard SNOMED-CT of alphabetic listing of ingredients permitted to recognise local clinical practice. Variations in the Indexesprescribe_by_brandWhere the prescribe_by_brand is set to 1, we do not supply a generic_prescribing_term or a generic_charting_term in the respective indexes. It is still possible to navigate from the data in the indexes to the generic records in the NZMT – see below. Records without termsThere are two records in the indexes that have no prescribing or charting terms. They are CTPPs 50168741000117100 (Metolazone (PHARMAC) 5 mg tablet: uncoated, 1 tablet) and 50168761000117101 (Hydralazine (PHARMAC) 25 mg, 1 tablet: uncoated). These entries were created to support the pharmacode, in its role as PHARMAC’s subsidy code at a time when PHARMAC and the NZULM did not know of the specific brands available. They are effectively dummy records which are retained in the NZULM to support clinical records that may contain these sctids. Pack level entriesThe example above is at Unit of Use level (MPUU & TPUU) but there are some products where the prescribing_term and charting_term is specified at pack level (MPP & TPP). This is because such products cannot be prescribed in terms of individual units of use. Prescribing and Charting Terms – a pack level exampleThis is a complex product with a very lengthy description. Even the prescribing and charting terms have required some abbreviation. The MPP records links to four MPUU records (three different strengths of levonorgestrel + ethinylestradiol and the inert tablet) and the TPP links to four TPUU records. Hence the prescribing and charting terms are not at Unit of Use level but at pack level.
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