DSTU2

This page is part of the FHIR Specification (v1.0.2: DSTU 2). The current version which supercedes this version is 5.0.0. For a full list of available versions, see the Directory of published versions . Page versions: R5 R4B R4 R3 R2

4.20.7 Resource Observation - Detailed Descriptions

Detailed Descriptions for the elements in the Observation resource.

Observation
Definition

Measurements and simple assertions made about a patient, device or other subject.

Control1..1
Requirements

Observations are a key aspect of healthcare. This resource is used to capture those that do not require more sophisticated mechanisms.

Alternate NamesVital Signs; Measurement; Results; Tests
Comments

Used for simple observations such as device measurements, laboratory atomic results, vital signs, height, weight, smoking status, comments, etc. Other resources are used to provide context for observations such as lab reports, etc.

InvariantsDefined on this element
obs-6: SHALL only be present if Observation.value[x] is not present (xpath: not(exists(f:dataAbsentReason)) or (not(exists(*[starts-with(local-name(.), 'value')]))))
obs-7: Component code SHALL not be same as observation code (xpath: not(exists(f:component/f:code)) or count(for $coding in f:code/f:coding return parent::*/f:component/f:code/f:coding[f:code/@value=$coding/f:code/@value and f:system/@value=$coding/f:system/@value])=0)
Observation.identifier
Definition

A unique identifier for the simple observation instance.

NoteThis is a business identifer, not a resource identifier (see discussion)
Control0..*
TypeIdentifier
Requirements

Allows observations to be distinguished and referenced.

Observation.status
Definition

The status of the result value.

Control1..1
BindingObservationStatus: Codes providing the status of an observation. (Required)
Typecode
Is Modifiertrue
Requirements

Need to track the status of individual results. Some results are finalized before the whole report is finalized.

Summarytrue
Observation.category
Definition

A code that classifies the general type of observation being made. This is used for searching, sorting and display purposes.

Control0..1
BindingObservation Category Codes: Codes for high level observation categories . (Example)
TypeCodeableConcept
Comments

The level of granularity is defined by the category concepts in the value set. More fine-grained filtering can be performed using the metadata and/or terminology hierarchy in Observation.code.

Observation.code
Definition

Describes what was observed. Sometimes this is called the observation "name".

Control1..1
BindingLOINC Codes: Codes identifying names of simple observations. (Example)
TypeCodeableConcept
Requirements

Knowing what kind of observation is being made is essential to understanding the observation.

Summarytrue
Observation.subject
Definition

The patient, or group of patients, location, or device whose characteristics (direct or indirect) are described by the observation and into whose record the observation is placed. Comments: Indirect characteristics may be those of a specimen, fetus, donor, other observer (for example a relative or EMT), or any observation made about the subject.

Control0..1
TypeReference(Patient | Group | Device | Location)
Requirements

Observations have no value if you don't know who or what they're about.

Summarytrue
Comments

One would expect this element to be a cardinality of 1..1. The only circumstance in which the subject can be missing is when the observation is made by a device that does not know the patient. In this case, the observation SHALL be matched to a patient through some context/channel matching technique, and at this point, the observation should be updated.

If the target of the observation is different than the subject, the general extension observation-focal-subject. may be used. However, the distinction between the patient's own value for an observation versus that of the fetus, or the donor or blood product unit, etc., are often specified in the observation code.

Observation.encounter
Definition

The healthcare event (e.g. a patient and healthcare provider interaction) during which this observation is made.

Control0..1
TypeReference(Encounter)
Requirements

For some observations it may be important to know the link between an observation and a particular encounter.

Observation.effective[x]
Definition

The time or time-period the observed value is asserted as being true. For biological subjects - e.g. human patients - this is usually called the "physiologically relevant time". This is usually either the time of the procedure or of specimen collection, but very often the source of the date/time is not known, only the date/time itself.

Control0..1
TypedateTime|Period
[x] NoteSee Choice of Data Types for further information about how to use [x]
Requirements

Knowing when an observation was deemed true is important to its relevance as well as determining trends.

Summarytrue
Comments

At least a date should be present unless this observation is a historical report.

Observation.issued
Definition

The date and time this observation was made available to providers, typically after the results have been reviewed and verified.

Control0..1
Typeinstant
Summarytrue
Comments

Updated when the result is updated.

Observation.performer
Definition

Who was responsible for asserting the observed value as "true".

Control0..*
TypeReference(Practitioner | Organization | Patient | RelatedPerson)
Requirements

May give a degree of confidence in the observation and also indicates where follow-up questions should be directed.

Summarytrue
Observation.value[x]
Definition

The information determined as a result of making the observation, if the information has a simple value.

Control0..1
TypeQuantity|CodeableConcept|string|Range|Ratio|SampledData|Attachment|time|dateTime|Period
[x] NoteSee Choice of Data Types for further information about how to use [x]
Requirements

An observation exists to have a value, though it may not if it is in error, or it represents a group of observations.

Summarytrue
Comments

Normally, an observation will have either a value or a set of related observations. A few observations (e.g. Apgar score) may have both a value and related observations (for an Apgar score, the observations from which the measure is derived). If a value is present, the datatype for this element should be determined by Observation.code. This element has a variable name depending on the type as follows: valueQuantity, valueCodeableConcept, valueString, valueRange, valueRatio, valueSampledData, valueAttachment, valueTime, valueDateTime, or valuePeriod. (The name format is "'value' + the type name" with a capital on the first letter of the type).

If the data element is usually coded or if the type associated with the Observation.value defines a coded value, use CodeableConcept instead of string datatype even if the value is uncoded text. A value set is bound to the ValueCodeableConcept element. For boolean values use valueCodeableConcept and select codes from HL7 Version 2 Table 0136. These "yes/no" concepts can be mapped to the display name "true/false" or other mutually exclusive terms that may be needed. For further discussion and examples see the notes section below.

Observation.dataAbsentReason
Definition

Provides a reason why the expected value in the element Observation.value[x] is missing.

Control0..1
BindingObservation Value Absent Reason: Codes specifying why the result (Observation.value[x]) is missing. (Extensible)
TypeCodeableConcept
Requirements

For many results it is necessary to handle exceptional values in measurements.

Comments

Null or exceptional values can be represented two ways in FHIR Observations. One way is to simply include them in the value set and represent the exceptions in the value. For example, measurement values for a serology test could be "detected", "not detected", "inconclusive", or "specimen unsatisfactory". The alternate way is to use the value element for actual observations and use the explicit dataAbsentReason element to record exceptional values. For example, the dataAbsentReason code "error" could be used when the measurement was not completed. Because of these options, use-case agreements are required to interpret general observations for exceptional values.

InvariantsAffect this element
obs-6: SHALL only be present if Observation.value[x] is not present (xpath: not(exists(f:dataAbsentReason)) or (not(exists(*[starts-with(local-name(.), 'value')]))))
Observation.interpretation
Definition

The assessment made based on the result of the observation. Intended as a simple compact code often placed adjacent to the result value in reports and flow sheets to signal the meaning/normalcy status of the result. Otherwise known as abnormal flag.

Control0..1
BindingObservation Interpretation Codes: Codes identifying interpretations of observations. (Extensible)
TypeCodeableConcept
Requirements

For some results, particularly numeric results, an interpretation is necessary to fully understand the significance of a result.

Alternate NamesAbnormal Flag
Observation.comments
Definition

May include statements about significant, unexpected or unreliable values, or information about the source of the value where this may be relevant to the interpretation of the result.

Control0..1
Typestring
Requirements

Need to be able to provide free text additional information.

Observation.bodySite
Definition

Indicates the site on the subject's body where the observation was made (i.e. the target site).

Control0..1
BindingSNOMED CT Body Structures: Codes describing anatomical locations. May include laterality. (Example)
TypeCodeableConcept
Requirements

Knowing where the observation is made is important for tracking if multiple sites are possible.

Comments

Only used if not implicit in code found in Observation.code. If the use case requires BodySite to be handled as a separate resource instead of an inline coded element (e.g. to identify and track separately) then use the standard extension body-site-instance.

Observation.method
Definition

Indicates the mechanism used to perform the observation.

Control0..1
BindingObservation Methods: Methods for simple observations. (Example)
TypeCodeableConcept
Requirements

In some cases, method can impact results and is thus used for determining whether results can be compared or determining significance of results.

Comments

Only used if not implicit in code for Observation.code.

Observation.specimen
Definition

The specimen that was used when this observation was made.

Control0..1
TypeReference(Specimen)
Comments

Observations are not made on specimens themselves; they are made on a subject, but usually by the means of a specimen. Note that although specimens are often involved, they are not always tracked and reported explicitly. Also note that observation resources may be used in contexts that track the specimen explicitly (e.g. Diagnostic Report).

Observation.device
Definition

The device used to generate the observation data.

Control0..1
TypeReference(Device | DeviceMetric)
Comments

An extension should be used if further typing of the device is needed. Devices used to support obtaining an observation can be represented using either extension or through the Observation.related element.

Observation.referenceRange
Definition

Guidance on how to interpret the value by comparison to a normal or recommended range.

Control0..*
Requirements

Knowing what values are considered "normal" can help evaluate the significance of a particular result. Need to be able to provide multiple reference ranges for different contexts.

Comments

Most observations only have one generic reference range. Systems MAY choose to restrict to only supplying the relevant reference range based on knowledge about the patient (e.g. specific to the patient's age, gender, weight and other factors), but this may not be possible or appropriate. Whenever more than one reference range is supplied, the differences between them SHOULD be provided in the reference range and/or age properties.

InvariantsDefined on this element
obs-3: Must have at least a low or a high or text (xpath: (exists(f:low) or exists(f:high)or exists(f:text)))
Observation.referenceRange.low
Definition

The value of the low bound of the reference range. The low bound of the reference range endpoint is inclusive of the value (e.g. reference range is >=5 - <=9). If the low bound is omitted, it is assumed to be meaningless (e.g. reference range is <=2.3).

Control0..1
TypeSimpleQuantity
InvariantsAffect this element
obs-3: Must have at least a low or a high or text (xpath: (exists(f:low) or exists(f:high)or exists(f:text)))
Observation.referenceRange.high
Definition

The value of the high bound of the reference range. The high bound of the reference range endpoint is inclusive of the value (e.g. reference range is >=5 - <=9). If the high bound is omitted, it is assumed to be meaningless (e.g. reference range is >= 2.3).

Control0..1
TypeSimpleQuantity
InvariantsAffect this element
obs-3: Must have at least a low or a high or text (xpath: (exists(f:low) or exists(f:high)or exists(f:text)))
Observation.referenceRange.meaning
Definition

Code for the meaning of the reference range.

Control0..1
BindingObservation Reference Range Meaning Codes: Code for the meaning of a reference range. (Example)
TypeCodeableConcept
Requirements

Need to be able to say what kind of reference range this is - normal, recommended, therapeutic, or perhaps what state this reference range applies to (i.e. age, hormonal cycles, etc.).

Comments

This SHOULD be populated if there is more than one range.

Observation.referenceRange.age
Definition

The age at which this reference range is applicable. This is a neonatal age (e.g. number of weeks at term) if the meaning says so.

Control0..1
TypeRange
Requirements

Some analytes vary greatly over age.

Observation.referenceRange.text
Definition

Text based reference range in an observation which may be used when a quantitative range is not appropriate for an observation. An example would be a reference value of "Negative" or a list or table of 'normals'.

Control0..1
Typestring
Observation.related
Definition

A reference to another resource (usually another Observation but could also be a QuestionnaireAnswer) whose relationship is defined by the relationship type code.

Control0..*
Requirements

Normally, an observation will have either a value or a set of related observations. A few observations (e.g. Apgar score) may have both a value and a set of related observations or sometimes QuestionnaireResponse from which the measure is derived.

Summarytrue
Comments

For a discussion on the ways Observations can assembled in groups together see Notes below.

Observation.related.type
Definition

A code specifying the kind of relationship that exists with the target resource.

Control0..1
BindingObservationRelationshipType: Codes specifying how two observations are related. (Required)
Typecode
Requirements

A relationship type SHOULD be provided.

Comments

"derived-from" is only logical choice when referencing QuestionnaireAnswer resource.

Observation.related.target
Definition

A reference to the observation or QuestionnaireResponse resource that is related to this observation.

Control1..1
TypeReference(Observation | QuestionnaireResponse)
Observation.component
Definition

Some observations have multiple component observations. These component observations are expressed as separate code value pairs that share the same attributes. Examples include systolic and diastolic component observations for blood pressure measurement and multiple component observations for genetics observations.

Control0..*
Requirements

Component observations share the same attributes in the Observation resource as the primary observation and are always treated a part of a single observation (they are not separable). However, the reference range for the primary observation value is not inherited by the component values and is required when appropriate for each component observation.

Summarytrue
Comments

For a discussion on the ways Observations can assembled in groups together see Notes below.

Observation.component.code
Definition

Describes what was observed. Sometimes this is called the observation "code".

Control1..1
BindingLOINC Codes: Codes identifying names of simple observations. (Example)
TypeCodeableConcept
Requirements

Knowing what kind of observation is being made is essential to understanding the observation.

Summarytrue
InvariantsAffect this element
obs-7: Component code SHALL not be same as observation code (xpath: not(exists(f:component/f:code)) or count(for $coding in f:code/f:coding return parent::*/f:component/f:code/f:coding[f:code/@value=$coding/f:code/@value and f:system/@value=$coding/f:system/@value])=0)
Observation.component.value[x]
Definition

The information determined as a result of making the observation, if the information has a simple value.

Control0..1
TypeQuantity|CodeableConcept|string|Range|Ratio|SampledData|Attachment|time|dateTime|Period
[x] NoteSee Choice of Data Types for further information about how to use [x]
Requirements

An observation exists to have a value, though it may not if it is in error, or it represents a group of observations.

Summarytrue
Comments

Normally, an observation will have either a value or a set of related observations. A few observations (e.g. Apgar score) may have both a value and related observations (for an Apgar score, the observations from which the measure is derived). If a value is present, the datatype for this element should be determined by Observation.code. A CodeableConcept with just a text would be used instead of a string if the field was usually coded, or if the type associated with the Observation.code defines a coded value. For boolean values use valueCodeableConcept and select codes from <http://hl7.org/fhir/ValueSet/v2-0136> (These "yes/no" concepts can be mapped to the display name "true/false" or other mutually exclusive terms that may be needed"). The element, Observation.value[x], has a variable name depending on the type as follows: valueQuantity, valueCodeableConcept, valueRatio, valueChoice, valuePeriod, valueSampleData, or valueString (The name format is "'value' + the type name" with a capital on the first letter of the type).

Observation.component.dataAbsentReason
Definition

Provides a reason why the expected value in the element Observation.value[x] is missing.

Control0..1
BindingObservation Value Absent Reason: Codes specifying why the result (Observation.value[x]) is missing. (Extensible)
TypeCodeableConcept
Requirements

For many results it is necessary to handle exceptional values in measurements.

Comments

"Null" or exceptional values can be represented two ways in FHIR Observations. One way is to simply include them in the value set and represent the exceptions in the value. For example, measurement values for a serology test could be "detected", "not detected", "inconclusive", or "test not done". The alternate way is to use the value element for actual observations and use the explicit dataAbsentReason element to record exceptional values. For example, the dataAbsentReason code "error" could be used when the measurement was not completed. Because of these options, use-case agreements are required to interpret general observations for exceptional values.

InvariantsAffect this element
obs-6: SHALL only be present if Observation.value[x] is not present (xpath: not(exists(f:dataAbsentReason)) or (not(exists(*[starts-with(local-name(.), 'value')]))))
Observation.component.referenceRange
Definition

Guidance on how to interpret the value by comparison to a normal or recommended range.

Control0..*
TypeSee Observation.referenceRange
Requirements

Knowing what values are considered "normal" can help evaluate the significance of a particular result. Need to be able to provide multiple reference ranges for different contexts.

Comments

Most observations only have one generic reference range. Systems MAY choose to restrict to only supplying the relevant reference range based on knowledge about the patient (e.g. specific to the patient's age, gender, weight and other factors), but this may not be possible or appropriate. Whenever more than one reference range is supplied, the differences between them SHOULD be provided in the reference range and/or age properties.