The value contains the numerical value of the quantity, including an implicit precision. If no comparator is specified, the value is a point value (i.e. ‘=’). The comparator element can never be ignored. The unit element contains a displayable unit that defines what is measured. The unit may additionally be coded in some formal way using the code and the system.
If the unit can be coded in UCUM (Unified Code for Units of Measure) and a code is provided, it should be a UCUM code. If a UCUM unit is provided in the code, then a canonical value can be generated for purposes of comparison between quantities. It is to be noted that the unit element will often contain text that is a valid UCUM unit, but it cannot be assumed that the unit actually contains a valid UCUM unit.
Fast Healthcare Interoperability Resources (FHIR) is a draft standard describing data formats and elements (known as “resources”) and an application programming interface (API) for exchanging electronic health records. The standard was created by the Health Level Seven International (HL7) health-care standards organization.
Its goal is to facilitate interoperation between legacy healthcare systems, to make it easy to provide healthcare information to healthcare providers and individuals on a wide variety of devices from computers to tablets to cell phones, and to allow third-party application developers to provide medical applications which can be easily integrated into existing systems.
FHIR provides an alternative to document-centric approaches by directly exposing discrete data elements as services. For example, basic elements of healthcare like patients, admissions, diagnostic reports and medications can each be retrieved and manipulated via their own resource URLs (Uniform Resource Locators). FHIR was supported at an American Medical Informatics Association meeting by many EHR (Electronic Health Record) vendors which value its open and extensible nature.