Overview of the Veterans Health Administration’s National Drug Formulary Reference Terminology (NDF RT)
Figure 6-1 depicts NDF-RT, a drug terminology knowledge base derived from the U.S. Department of Veterans Affairs’ (VA) National Drug File. NDF-RT was developed over the past 5 years with input from a variety of government and other stakeholders. The figure outlines NDF-RT’s structure, and may be interpreted as follows. Each triangle represents a hierarchy of related concept definitions, with labels explained below. Thick arrows represent additional hierarchical connections. Solid black and dotted arrows represent semantic relationships. The triangles represent data contained in NDF-RT.
The heart of NDF-RT is labeled VA Product, such as ASPIRIN 325MG ORAL TABLET. The VA Product is generally equivalent to the RxNORM Semantic Clinical Drug. Each VA Product is a “child” of two separate parents, a VA Class (e.g., ANALGESICS) and a Drug Preparation (e.g., ASPIRIN PREPARATIONS). Drug Preparations are described by relationships to their Mechanism(s) of Action (MoA triangle) (function at the cellular or subcellular level), Physiologic Effect(s) (PE triangle) (function at the organ, tissue, or body system level), and Disease State actions (diseases treated, caused, or prevented by the drug).
Each VA Product also is characterized by its therapeutically active Chemical Ingredient(s), which in turn are characterized according to a structural class. In addition, each VA Product has a Dose Form (e.g., ORAL TABLET); a VA Dispense Units entry (e.g., TABLET); and a variety of other attributes, including links to RxNORM and commercial drug knowledge bases (not shown).
For each active ingredient in a VA Product, there is an entry in the Unit Str. (Unit and Strength) hierarchy (325MG in the aspirin example).
Each VA Product also encompasses some number of Packaged Products, which are identified by National Drug Code (NDC) numbers from the Food and Drug Administration (FDA).
Each Packaged Product includes dispensing information, such as Route of Administration (RoA) (e.g., ORAL, INTRAMUSCULAR), Package Type (Pkg. Type) (e.g., BOX or BOTTLE), Package Size (Pkg. Size) (e.g., 500, 8 FL OZ), and Manufacturer (e.g., LILLY, SEARLE).
NDF-RT’s multiaxial hierarchical structure is designed to provide a balance of rigor in terminology and compatibility with deployed systems, while simultaneously streamlining the maintenance required to keep pace with the thousands of changes to drug products that occur each month. Existing and planned extensions to NDF-RT (not shown) support a variety of clinical decision-support cases, such as dose adjustment based on individual pharmacogenomic characteristics. Currently, the VA is extending a commercial terminology management system to support the semiautomated integration of data from pharmacy personnel, the FDA’s Structured Product Label (SPL) project, and commercial drug knowledge sources.