Providers of medical informatics applications need controlled medical vocabularies to support their applications. It is to their advantage to use available standards to achieve this end. Various standards have long existed; each with the purpose to cover a specific area within healthcare. For example, the first international classification created by WHO is known as the International List of Causes of Death (ICD), which was adopted by the International Statistical Institute in 1893 (WHO.int) . In addition to international standards, numerous local lists of terms are used in order to cover different medical events.
Healthcare as a field is constantly growing and evolving, which means the standard medical vocabularies are under constant maintenance in order to cover and define newly discovered diseases, procedures, medications, etc. This maintenance is of paramount importance to keep the standard relevant and useful. However, there are a lot of pitfalls connected to this maintenance.
First of all, the technical choices can impact the capacity of a terminology to evolve, change, and remain usable over time. For example, the definition of how a term’s code is managed and how it can behave in a medical vocabulary is important. A code for a medical event should never change or be reused, as it is highly likely that historical patient data become ambiguous or erroneous. Furthermore, codes for each medical event should not have a format that can carry meaning, context or be tied to a hierarchical position. This is very important as health knowledge is being constantly updated and therefore how we categorize health terms is likely to change.
A standard vocabulary should support consistency of patient descriptions over time, however, is not possible when terms change or even worse if a term inside a vocabulary changes meaning. In practice, this problem can be dangerous to the management of individual patients whose data might be subsequently misinterpreted. Therefore, everything attached to a medical code such as name, properties or relationship must remain the same meaning as was first intended, thereby following the principle of “Concept Permanence”.
Historic Information as a Potential Solution:
The above issue of maintenance seems straightforward, however, terminology providers change and add names, relationships and properties for a given medical event. This has the potential to change the interpretation of the term. One solution to overcome this issue is to have a full historical timeline for a medical term. This historical information is essential because the interpretation of coded patient data is a function of a term that exists at a certain point in time (e.g. AIDS patients were coded inconsistently before the introduction of the term AIDS). Possessing a full historic view of medical terms provides the ability to describe how a term was interpreted at a given point in time and thereby correctly extract the intended meaning. In order to have this full record of history, all new and revised terms and synonyms must have their date of entry as well as date of retirement recorded in the code system.
How Can HealthTerm Help?
HealthTerm is a terminology solution where both international standards and local term sets can be managed and maintained. All modifications and updates of a term will be tracked resulting in a historic timeline of a term and its adhering components. Furthermore, nothing is deleted to support historical patient records using obsolete terms, for their future interpretation and aggregation.
Peter L Elkin, Steven H. Bown, Christopher G. Chute. Guideline for Health Informatics: Controlled Health Vocabularies – Vocabulary Structure and High-level Indicators. Volume 84: MEDINFO 2001, pages: 191 – 195