Quantity

• Datatypes
• Definitions
• Examples
• Mappings
• Profiles

Overview

See also Examples, Detailed Descriptions, Mappings, Profiles and Extensions

A measured amount (or an amount that can potentially be measured).

This datatype can be bound to a ValueSet.

[%dt Quantity 4%]

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 (see Coding for further information about how to use the system element).

If the unit can be coded in UCUM 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. Note 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.

If there is a need to convey exceptional values such as Not a Number (NaN), 'trace', 'sufficient quantity', etc., this should be done using a coded data type such as CodeableConcept, drawing on codes from code systems such as Data Absent Reason or Null Flavor, and appropriate extensions exist for this purpose (here and here).

Constraints

[%dt.constraints Quantity%]

The context of use may frequently define what kind of measured quantity this is and therefore what kind of unit can be used. The context of use may additionally require a code from a particular system, or a value set - see Using Terminologies for information about binding a Quantity to a value set to constrain the unit codes. The context of use may also restrict the values for the value or comparator.

[%tx Quantity%]

Quantity is used in the following places: [%dtusage Quantity%]

Defined Variations on Quantity

There are several additional datatypes that are specializations of Quantity that only introduce new restrictions on the existing elements defined as part of the Quantity datatype.

Distance

Distance

Count

Duration

In addition to the specializations, there is one constraint on Quantity used in several resources:

Simple Quantity

Note that the constraint is different from the other specializations of Quantity because it is not a type, just rules applied where the Quantity type is used. There's another constraint - see Money immediately below.

Elements

• Quantity.value [0..1]: decimal The value of the measured amount. The value includes an implicit precision in the presentation of the value
• Quantity.comparator [0..1]: code How the value should be understood and represented - whether the actual value is greater or less than the stated value due to measurement issues; e.g. if the comparator is "<" , then the real value is < stated value
• Quantity.unit [0..1]: string A human-readable form of the unit
• Quantity.system [0..1]: uri The identification of the system that provides the coded form of the unit
• Quantity.code [0..1]: code A computer processable form of the unit in some unit representation system

Bindings

• Quantity.comparator: QuantityComparator | strength: code list | reference: #quantity-comparator
• Quantity.code: !

Modifiers

• Quantity.comparator: Is modifier

Requirements

• Quantity.value: Precision is handled implicitly in almost all cases of measurement
• Quantity.comparator: Need a framework for handling measures where the value is <5ug/L or >400mg/L due to the limitations of measuring methodology.
• Quantity.unit: There are many representations for units of measure and in many contexts, particular representations are fixed and required. I.e. mcg for micrograms
• Quantity.system: Need to know the system that defines the coded form of the unit
• Quantity.code: Need a computable form of the unit that is fixed across all forms. UCUM provides this for quantities, but SNOMED CT provides many units of interest

Comments

• Quantity.value: The implicit precision in the value should always be honored. Monetary values have their own rules for handling precision (refer to standard accounting text books)
• Quantity.code: The preferred system is UCUM, but SNOMED CT can also be used (for customary units) or ISO 4217 for currency. The context of use may additionally require a code from a particular system

Order and Missing Meaning

• Quantity.comparator: Missing: If there is no comparator, then there is no modification of the value

Mappings

• Quantity.value: RIM Mapping: PQ.value, CO.value, MO.value, IVL.high or IVL.low depending on the value
• Quantity.value: v2 Mapping: SN.2 / CQ - N/A
• Quantity.comparator: RIM Mapping: IVL properties
• Quantity.comparator: v2 Mapping: SN.1 / CQ.1
• Quantity.unit: RIM Mapping: PQ.unit
• Quantity.unit: v2 Mapping: (see OBX.6 etc.) / CQ.2
• Quantity.system: RIM Mapping: CO.codeSystem, PQ.translation.codeSystem
• Quantity.system: v2 Mapping: (see OBX.6 etc.) / CQ.2
• Quantity.code: RIM Mapping: PQ.code, MO.currency, PQ.translation.code
• Quantity.code: v2 Mapping: (see OBX.6 etc.) / CQ.2