The terms reference range and measurement range are used interchangeably even though, for a clinician, the reference range has particular meaning and use. The latter is meant as an abstraction of all sorts of ranges on measurements, including reference ranges and therapeutic ranges. |
Measurement ranges are defined in the following, different resources:
ActivityDefinition, in the extension ActivityDefinition.ehealth-referenceRange. These are generic, that is, non-patient specific ranges applicable for the particular activity, say, a measurement of oxygen saturation.
ServiceRequest, in the extension ServiceRequest.ehealth-referenceRange. These are patient-specific ranges applicable to the particular activity in the particular CarePlan referencing the ServiceRequest. A Patient can have multiple CarePlan with multiple ServiceRequest and therefore, possibly differing measurement ranges even for the same activity type, say, measurement of oxygen saturation.
Observation, in the element Observation.referenceRange
As is reflected in the cardinality, multiple reference ranges can be defined simultaneously. Upon submission of an Observation, the reference ranges defined in the referenced ServiceRequest are copied to the Observation by the service. This way, the set of measurement ranges in effect at the time of submission are captured in the Observation, regardless of how the Patient-specific reference ranges in ServiceRequest are maintained and altered.
The structure used in the extension ehealth-referenceRange contains the following subset of elements defined in Observation.referenceRange:
low - the lower end of the range
high - the higher end of the range
type - the type of measurement range
In the figure below, example measurement ranges have been given as absolute measurement ranges. Absolute measurement ranges are always given in the same unit as measured/submitted values.
The normal range shown in green with a dotted outline is currently not supported. The definition of normal measurement ranges would allow for more credible statements about measured (and submitted) values. |
In the figure below, example measurement ranges have been given as relative measurement ranges. Relative measurement ranges can be given:
as percentage change
as unit percent if measured/submitted values are not already given as percent.
as unit percent point if measured/submitted values are already given as percent.
as the same unit as measured/submitted values
The normal range shown in green with a dotted outline is currently not supported. The definition of normal measurement ranges would allow for more credible statements about measured (and submitted) values. |
Certain use of relative reference ranges involves an automated processing type of Library (see https://ehealth-dk.atlassian.net/wiki/spaces/EDTW/pages/1251409937/Library+Resources#Assessment-of-Relative-Reference-Ranges-Library-and-Rule) which compares a submitted measurement against a reference base.
The reference base is captured in an FHIR Goal with the following characteristics:
the description is Coding for reference-value (see https://ehealth.sundhed.dk/fhir/ValueSet-ehealth-goal-description.html)
lifeCycleStatus is accepted
start has a startDate
target.measure is an observation code in the ValueSet goal-target-measure similar to that of the corresponding ActivityDefinition
For an ActivityDefinition with code being a Coding of Blood Pressure (or other composite measurement), the Goal should contain a number of targets, each with the respective target.measure matching a component of the composite measurement (e.g. systolic and diastolic blood pressure for blood pressure).
target.detailQuantity contains the actual reference base value (and unit). The reference base value can be
addresses is a reference to the ServiceRequest where the relative reference range is maintained.
The Goal shall be added to CarePlan.goal in the CarePlan referencing the ServiceRequest the relative reference range is maintained. As time goes on, an additional Goal that supersedes the previous Goal can be added. This approach shall be used instead of simply adjusting the reference base value of an existing Goal.
The Library described in https://ehealth-dk.atlassian.net/wiki/spaces/EDTW/pages/1251409937/Library+Resources#Assessment-of-Relative-Reference-Ranges-Library-and-Rule favours the FHIR Goal with the most recent start.startDate.
Certain considerations should be made when maintaining measurement ranges in the eHealth Infrastructure. For the current list of allowed measurement range types, some can overlap and some typically should not, or at least only at their low or high bounds.
In principle, each measurement range can be well-defined in itself. Also in principle, it should be possible to state facts and perform triaging simply by comparing a measured, submitted value against all the corresponding measurement ranges. For instance, a submitted value of 75.0 kg could be stated as:
be within the absolute measurement range for a yellow alarm
be within the absolute measurement range for a red alarm
be outside the absolute, normal measurement range
This could be triaged by creating:
a Task with a priority corresponding to the red alarm
a Task with a priority corresponding to the yellow alarm
The measurement ranges shown above overlap in boundaries only. It is up to the clinician's discretion whether to allow overlaps beyond boundaries.
In automated rules (See Processing of Automated Processing Rules), boundary overlaps shall, unless stated explicitly otherwise, be handled by choosing the worst-case situation. For the above submitted value of 75.0 kg, such preference results in:
stating that the (submitted) is within the absolute measurement range for a red alarm
stating that the (submitted) is outside the absolute, normal measurement range
a Task with a priority corresponding to the red alarm
Automated rules (See Processing of Automated Processing Rules), do not handle non-boundary overlaps in measurement ranges unless stated explicitly otherwise.