FHIR R4 Current Build
This is the current officially released version of FHIR, which is R4 (v4.0.0). For a full list of all versions, see the Directory of published versions .
Orders and Observations Work Group Maturity Level : N   Normative (from v4.0.0) v4.1.0) Security Category : Patient Compartments : Device , Encounter , Patient , Practitioner , RelatedPerson
This page has been approved as part of an ANSI standard. See the Observation Package for further details.

Detailed Descriptions for the elements in the Observation resource.

Observation
Element Id Observation
Definition

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

Cardinality 0..*
Type DomainResource
Requirements

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

Alternate Names Vital 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 laboratory reports, etc.

Invariants
Defined on this element
obs-6 Rule dataAbsentReason SHALL only be present if Observation.value[x] is not present dataAbsentReason.empty() or value.empty()
obs-7 Rule If Observation.code is the same as an Observation.component.code then the value element associated with the code SHALL NOT be present value.empty() or component.code.where( (coding.code = %resource.code.coding.code) and (coding.system = %resource.code.coding.system)).empty() component.code.where(coding.intersect(%resource.code.coding).exists()).empty()
Observation.identifier
Element Id Observation.identifier
Definition

A unique identifier assigned to this observation.

Note This is a business identifier, not a resource identifier (see discussion )
Cardinality 0..*
Type Identifier
Requirements

Allows observations to be distinguished and referenced.

Summary true
Observation.basedOn
Element Id Observation.basedOn
Definition

A plan, proposal or order that is fulfilled in whole or in part by this event. For example, a MedicationRequest may require a patient to have laboratory test performed before it is dispensed.

Cardinality 0..*
Type Reference ( CarePlan | DeviceRequest | ImmunizationRecommendation | MedicationRequest | NutritionOrder | ServiceRequest )
Patterns Reference(CarePlan,DeviceRequest,ImmunizationRecommendation,MedicationRequest,NutritionOrder,ServiceRequest): Common patterns = Request
Requirements

Allows tracing of authorization for the event and tracking whether proposals/recommendations were acted upon.

Alternate Names Fulfills
Summary true
Observation.partOf
Element Id Observation.partOf
Definition

A larger event of which this particular Observation is a component or step. For example, an observation as part of a procedure.

Cardinality 0..*
Type Reference ( MedicationAdministration | MedicationDispense | MedicationStatement MedicationUsage | Procedure | Immunization | ImagingStudy )
Patterns Reference(MedicationAdministration,MedicationDispense,MedicationUsage,Procedure,Immunization,ImagingStudy): Common patterns = Event
Alternate Names Container
Summary true
Comments

To link an Observation to an Encounter use encounter . See the Notes below for guidance on referencing another Observation.

Observation.status
Element Id Observation.status
Definition

The status of the result value.

Cardinality 1..1
Terminology Binding ObservationStatus ( Required )
Type code
Is Modifier true (Reason: This element is labeled as a modifier because it is a status element that contains status entered-in-error which means that the resource should not be treated as valid)
Requirements

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

Summary true
Comments

This element is labeled as a modifier because the status contains codes that mark the resource as not currently valid.

Observation.category
Element Id Observation.category
Definition

A code that classifies the general type of observation being made.

Cardinality 0..*
Terminology Binding Observation Category Codes ( Preferred )
Type CodeableConcept
Requirements

Used for filtering what observations are retrieved and displayed.

Comments

In addition to the required category valueset, this element allows various categorization schemes based on the owner’s definition of the category and effectively multiple categories can be used at once. The level of granularity is defined by the category concepts in the value set.

Observation.code
Element Id Observation.code
Definition

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

Cardinality 1..1
Terminology Binding LOINC Codes ( Example )
Type CodeableConcept
Requirements

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

Alternate Names Name
Summary true
Comments

All code-value and, if present, component.code-component.value pairs need to be taken into account to correctly understand the meaning of the observation.

Observation.subject
Element Id Observation.subject
Definition

The patient, or group of patients, location, or device this observation is about and into whose record the observation is placed. If the actual focus of the observation is different from the subject (or a sample of, part, or region of the subject), the focus element or the code itself specifies the actual focus of the observation.

Cardinality 0..1
Type Reference ( Patient | Group | Device | Location )
Patterns Reference(Patient,Group,Device,Location): Common patterns = Participant
Requirements

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

Summary true
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.

Observation.focus
Element Id Observation.focus
Definition

The actual focus of an observation when it is not the patient of record representing something or someone associated with the patient such as a spouse, parent, fetus, or donor. For example, fetus observations in a mother's record. The focus of an observation could also be an existing condition, an intervention, the subject's diet, another observation of the subject, or a body structure such as tumor or implanted device. An example use case would be using the Observation resource to capture whether the mother is trained to change her child's tracheostomy tube. In this example, the child is the patient of record and the mother is the focus.

Cardinality 0..*
Type Reference ( Any )
Summary true
Comments

Typically, an observation is made about the subject - a patient, or group of patients, location, or device - and the distinction between the subject and what is directly measured for an observation is specified in the observation code itself ( e.g., "Blood Glucose") and does not need to be represented separately using this element. Use specimen if a reference to a specimen is required. If a code is required instead of a resource use either bodysite for bodysites or the standard extension focusCode .

Observation.encounter
Element Id Observation.encounter
Definition

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

Cardinality 0..1
Type Reference ( Encounter )
Requirements

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

Alternate Names Context
Summary true
Comments

This will typically be the encounter the event occurred within, but some events may be initiated prior to or after the official completion of an encounter but still be tied to the context of the encounter (e.g. pre-admission laboratory tests).

Observation.effective[x]
Element Id 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.

Cardinality 0..1
Type dateTime | Period | Timing | instant
[x] Note See 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.

Alternate Names Occurrence
Summary true
Comments

At least a date should be present unless this observation is a historical report. For recording imprecise or "fuzzy" times (For example, a blood glucose measurement taken "after breakfast") use the Timing datatype which allow the measurement to be tied to regular life events.

Observation.issued
Element Id Observation.issued
Definition

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

Cardinality 0..1
Type instant
Summary true
Comments

For Observations that don’t require review and verification, it may be the same as the lastUpdated time of the resource itself. For Observations that do require review and verification for certain updates, it might not be the same as the lastUpdated time of the resource itself due to a non-clinically significant update that doesn’t require the new version to be reviewed and verified again.

Observation.performer
Element Id Observation.performer
Definition

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

Cardinality 0..*
Type Reference ( Practitioner | PractitionerRole | Organization | CareTeam | Patient | RelatedPerson )
Patterns Reference(Practitioner,PractitionerRole,Organization,CareTeam,Patient,RelatedPerson): Common patterns = Participant
Requirements

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

Summary true
Observation.value[x]
Element Id Observation.value[x]
Definition

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

Cardinality 0..1
Type Quantity | CodeableConcept | string | boolean | integer | Range | Ratio | SampledData | time | dateTime | Period
[x] Note See Choice of Data Types for further information about how to use [x]
Requirements

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

Summary true
Comments

An observation may have; 1) a single value here, 2) both a value and a set of related or component values, or 3) only a set of related or component values. 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 additional guidance, see the Notes section below.

Invariants
Affect this element
obs-7 Rule If Observation.code is the same as an Observation.component.code then the value element associated with the code SHALL NOT be present value.empty() or component.code.where( (coding.code = %resource.code.coding.code) and (coding.system = %resource.code.coding.system)).empty() component.code.where(coding.intersect(%resource.code.coding).exists()).empty()
Observation.dataAbsentReason
Element Id Observation.dataAbsentReason
Definition

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

Cardinality 0..1
Terminology Binding DataAbsentReason ( Extensible )
Type CodeableConcept
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. Note that an observation may only be reported if there are values to report. For example differential cell counts values may be reported only when > 0. Because of these options, use-case agreements are required to interpret general observations for null or exceptional values.

Invariants
Affect this element
obs-6 Rule dataAbsentReason SHALL only be present if Observation.value[x] is not present dataAbsentReason.empty() or value.empty()
Observation.interpretation
Element Id Observation.interpretation
Definition

A categorical assessment of an observation value. For example, high, low, normal.

Cardinality 0..*
Terminology Binding Observation Interpretation Codes ( Extensible )
Type CodeableConcept
Requirements

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

Alternate Names Abnormal Flag
Comments

Historically used for laboratory results (known as 'abnormal flag' ), its use extends to other use cases where coded interpretations are relevant. Often reported as one or more simple compact codes this element is often placed adjacent to the result value in reports and flow sheets to signal the meaning/normalcy status of the result.

Observation.note
Element Id Observation.note
Definition

Comments about the observation or the results.

Cardinality 0..*
Type Annotation
Requirements

Need to be able to provide free text additional information.

Comments

May include general statements about the observation, or statements about significant, unexpected or unreliable results values, or information about its source when relevant to its interpretation.

Observation.bodySite
Element Id Observation.bodySite
Definition

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

Cardinality 0..1
Terminology Binding SNOMED CT Body Structures ( Example )
Type CodeableConcept
Comments

Only used if not implicit in code found in Observation.code. In many systems, this may be represented as a related observation instead of an inline component.

If the use case requires BodySite to be handled as a separate resource (e.g. to identify and track separately) then use the standard extension bodySite .

Observation.method
Element Id Observation.method
Definition

Indicates the mechanism used to perform the observation.

Cardinality 0..1
Terminology Binding Observation Methods ( Example )
Type CodeableConcept
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
Element Id Observation.specimen
Definition

The specimen that was used when this observation was made.

Cardinality 0..1
Type Reference ( Specimen )
Comments

Should only be used if not implicit in code found in Observation.code . Observations are not made on specimens themselves; they are made on a subject, but in many cases 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
Element Id Observation.device
Definition

The device used to generate the observation data.

Cardinality 0..1
Type Reference ( Device | DeviceMetric )
Patterns Reference(Device,DeviceMetric): No common pattern
Comments

Note that this is not meant to represent a device involved in the transmission of the result, e.g., a gateway. Such devices may be documented using the Provenance resource where relevant.

Observation.referenceRange
Element Id Observation.referenceRange
Definition

Guidance on how to interpret the value by comparison to a normal or recommended range. Multiple reference ranges are interpreted as an "OR". In other words, to represent two distinct target populations, two referenceRange elements would be used.

Cardinality 0..*
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 might 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.

Invariants
Defined on this element
obs-3 Rule Must have at least a low or a high or text low.exists() or high.exists() or text.exists()
Observation.referenceRange.low
Element Id 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).

Cardinality 0..1
Type SimpleQuantity
Invariants
Affect this element
obs-3 Rule Must have at least a low or a high or text low.exists() or high.exists() or text.exists()
Observation.referenceRange.high
Element Id 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).

Cardinality 0..1
Type SimpleQuantity
Invariants
Affect this element
obs-3 Rule Must have at least a low or a high or text low.exists() or high.exists() or text.exists()
Observation.referenceRange.type
Element Id Observation.referenceRange.type
Definition

Codes to indicate the what part of the targeted reference population it applies to. For example, the normal or therapeutic range.

Cardinality 0..1
Terminology Binding Observation Reference Range Meaning Codes ( Preferred )
Type CodeableConcept
Requirements

Need to be able to say what kind of reference range this is - normal, recommended, therapeutic, etc., - for proper interpretation.

Comments

This SHOULD be populated if there is more than one range. If this element is not present then the normal range is assumed.

Observation.referenceRange.appliesTo
Element Id Observation.referenceRange.appliesTo
Definition

Codes to indicate the target population this reference range applies to. For example, a reference range may be based on the normal population or a particular sex or race. Multiple appliesTo are interpreted as an "AND" of the target populations. For example, to represent a target population of African American females, both a code of female and a code for African American would be used.

Cardinality 0..*
Terminology Binding Observation Reference Range Applies To Codes ( Example )
Type CodeableConcept
Requirements

Need to be able to identify the target population for proper interpretation.

Comments

This SHOULD be populated if there is more than one range. If this element is not present then the normal population is assumed.

Observation.referenceRange.age
Element Id 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.

Cardinality 0..1
Type Range
Requirements

Some analytes vary greatly over age.

Observation.referenceRange.text
Element Id 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".

Cardinality 0..1
Type string
Observation.hasMember
Element Id Observation.hasMember
Definition

This observation is a group observation (e.g. a battery, a panel of tests, a set of vital sign measurements) that includes the target as a member of the group.

Cardinality 0..*
Type Reference ( Observation | QuestionnaireResponse | MolecularSequence )
Patterns Reference(Observation,QuestionnaireResponse,MolecularSequence): No common pattern
Summary true
Comments

When using this element, an observation will typically have either a value or a set of related resources, although both may be present in some cases. For a discussion on the ways Observations can assembled in groups together, see Notes below. Note that a system may calculate results from QuestionnaireResponse into a final score and represent the score as an Observation.

Observation.derivedFrom
Element Id Observation.derivedFrom
Definition

The target resource that represents a measurement from which this observation value is derived. For example, a calculated anion gap or a fetal measurement based on an ultrasound image.

Cardinality 0..*
Type Reference ( DocumentReference | ImagingStudy | Media | QuestionnaireResponse | Observation | MolecularSequence )
Patterns Reference(DocumentReference,ImagingStudy,QuestionnaireResponse,Observation,MolecularSequence): No common pattern
Summary true
Comments

All the reference choices that are listed in this element can represent clinical observations and other measurements that may be the source for a derived value. The most common reference will be another Observation. For a discussion on the ways Observations can assembled in groups together, see Notes below.

Observation.component
Element Id 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.

Cardinality 0..*
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.

Summary true
Comments

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

Observation.component.code
Element Id Observation.component.code
Definition

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

Cardinality 1..1
Terminology Binding LOINC Codes ( Example )
Type CodeableConcept
Requirements

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

Summary true
Comments

All code-value and component.code-component.value pairs need to be taken into account to correctly understand the meaning of the observation.

Observation.component.value[x]
Element Id Observation.component.value[x]
Definition

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

Cardinality 0..1
Type Quantity | CodeableConcept | string | boolean | integer | Range | Ratio | SampledData | time | dateTime | Period
[x] Note See Choice of Data Types for further information about how to use [x]
Requirements

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

Summary true
Comments

Used when observation has a set of component observations. An observation may have both a value (e.g. an Apgar score) and component observations (the observations from which the Apgar score was 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 additional guidance, see the Notes section below.

Observation.component.dataAbsentReason
Element Id Observation.component.dataAbsentReason
Definition

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

Cardinality 0..1
Terminology Binding DataAbsentReason ( Extensible )
Type CodeableConcept
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.

Invariants
Affect this element
obs-6 Rule dataAbsentReason SHALL only be present if Observation.value[x] is not present dataAbsentReason.empty() or value.empty()
Observation.component.interpretation
Element Id Observation.component.interpretation
Definition

A categorical assessment of an observation value. For example, high, low, normal.

Cardinality 0..*
Terminology Binding Observation Interpretation Codes ( Extensible )
Type CodeableConcept
Requirements

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

Alternate Names Abnormal Flag
Comments

Historically used for laboratory results (known as 'abnormal flag' ), its use extends to other use cases where coded interpretations are relevant. Often reported as one or more simple compact codes this element is often placed adjacent to the result value in reports and flow sheets to signal the meaning/normalcy status of the result.

Observation.component.referenceRange
Element Id Observation.component.referenceRange
Definition

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

Cardinality 0..*
Type See 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 might 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.