Creating and Maintaining Measurement Ranges

NOTE: THIS SECTION IS STILL UNDER CONSTRUCTION.

Please refer to the description of measurement ranges for details on how to define adjacent and possibly (but not typically) overlapping measurement ranges.

Setting up absolute reference ranges

An absolute reference range is set up by adding a ehealth-referenceRange structure to ServiceRequest.ehealth-referenceRange where:

ehealth-referenceRange.type is a Coding with:
- system: http://ehealth.sundhed.dk/cs/reference-range-type
- code: RAL or GAL, for red alarm absolute reference range and yellow alarm absolute reference range, respectively.
ehealth-referenceRange.low and/or .high is a:
- a SimpleQuantity where:
  - value: the integer or decimal value for the low/high boundary
  - unit: <same unit as measured value is expressed with>
  - system: <same system as measured value is expressed with>
  - code: <same code as measured value is expressed with>

Setting up relative reference ranges and reference base

A relative reference range is set up by adding a ehealth-referenceRange structure to ServiceRequest.ehealth-referenceRange where:

ehealth-referenceRange.type is a Coding with:
- system: http://ehealth.sundhed.dk/cs/reference-range-type
- code: RELRAL or RELGAL, for red alarm relative reference range and yellow alarm relative reference range, respectively.
ehealth-referenceRange.low and/or .high is either of:
- a SimpleQuantity for a percentage change (stated as percent point change to measurement already expressed in percent) compared to the reference base where:
  - value: the integer or decimal value for the low/high boundary
  - unit: percent point
  - system: http://ehealth.sundhed.dk/cs/ehealth-unit-code
  - code: percentpoint
- a SimpleQuantity for a percentage change (stated as percent change to measurement not already expressed in percent) compared to the reference base where:
  - value: the integer or decimal value for the low/high boundary
  - unit: percent
  - system: http://unitsofmeasure.org
  - code: %
- a SimpleQuantity for a relative change compared to the reference base where:
  - value: the integer or decimal value for the low/high boundary
  - unit: <same unit as measured value is expressed with>
  - system: <same system as measured value is expressed with>
  - code: <same code as measured value is expressed with>

A relative reference range states a change relative to some reference base. This way, a measured value can be compared to a reference base taking the relative reference range into account.

There are several ways to find a reference base:

searching for a prior, measured value, say, the highest/lowest/most recent/oldest value in some given period of time
a derivate, say, an average of measured values in some given period of time
a designated value, either copied from and/or referencing a measured value

The Goal resource described in the following is available as of eHealth Infrastructure Release 7. For now, it can be accessed as Goal.

To add a designated reference base, create a Goal with:

status: accepted
description: A Coding with:
- code: reference-value
- system: http://ehealth.sundhed.dk/cs/goal-description
subject: Reference to Patient
startDate: A datetime representing the starting point at which this reference base is applicable
target.measure: Coding (the same as code in the ProcedureRequest as the relative reference range is defined in)
target.detailQuantity: A Quantity containing the reference base value
addresses: Reference to ProcedureRequest (the same ProcedureRequest as the relative reference range is defined in)
addresses: Reference to the Observation from which the value in target.detailQuantity has been copied (if that is the case)

A reference to the Goal shall then be added to the CarePlan (same CarePlan that references the ProcedureRequest) to:

CarePlan.goal

Over time, the relative reference ranges can change and new Goal resources can be created and added to the CarePlan.

Example use of relative reference range stated in percent point.

A measurement of oxygen saturation is submitted as an Observation where the Observation.valueQuantity is a Quantity with:

value: 88
unit: percent
system: http://unitsofmeasure.org
code: %

A red alarm relative reference range given as zero to -5 percent point is stated as:

ehealth-referenceRange.type is a Coding with:
- system: http://ehealth.sundhed.dk/cs/reference-range-type
- code: RELRAL for red alarm relative reference range type
ehealth-referenceRange.low is a SimpleQuantity with:
- value: -5.0
- unit: percent point
- system: http://ehealth.sundhed.dk/cs/ehealth-unit-code
- code: percentpoint
ehealth-referenceRange.high is a SimpleQuantity with:
- value: -2.0
- unit: percent point
- system: http://ehealth.sundhed.dk/cs/ehealth-unit-code
- code: percentpoint

A reference base could be defined as a Goal where Goal.target.detailQuantity is a Quantity with:

value: 92
unit: percent
system: http://unitsofmeasure.org
code: %

Because the measured value 88% is within a range of [-5; -2] percent point relative to the reference base value 92%, this would constitute a value which lies within the red alarm relative reference range.

If the designated reference base was instead 95%, the measured value of 88% would not be within the red alarm relative reference range.