Dates and Times

2.2.13

The HL7 Act class includes two attributes related to the temporal situation of an action (Act.effectiveTime, Act.activityTime [[[7]]]). In addition, each participation in an Act may have an associated time (for example, author.time or performed.time). Each of these times can be expressed either as a point-in-time or a period of time.

2.2.13.1

The SNOMED CT [ 408731000 | temporal context ] distinguishes between findings or procedures that are recorded as part of "past" history and those that are recorded as [ 15240007 | current ]. It also allows a distinction to be made between a specified point or period in time (e.g. and a more general unspecified time (e.g. [ 410588008 | past - unspecified ]). The [ 408731000 | temporal context ] potentially affects the interpretation HL7 date and time attributes.

When a SNOMED CT expression (or concept definition) includes an explicit representation of [ 408731000 | temporal context ], the effectiveTime might be interpreted either as "the time at which the situation applied" or "the time at which the focus concept applied". Guidance is needed to avoid this potentially misleading ambiguity.

• For example, the definition of the concept [407553003 | history of - glandular fever] includes:
  • [ 246090004 | associated finding | = 271558008 | glandular fever | , 408731000 | temporal context | = 410513005 | past ]
    • The concept [407553003 | history of - glandular fever] represents a situation.
    • The value of the associated finding attribute is the focus concept (i.e. the concept [ 271558008 | glandular fever ]).
  • When an Observation asserts the value [407553003 | history of - glandular fever], the effectiveTime might be interpreted as:
    • The time when the focus concept applied (i.e. the time in the past when they actually had glandular fever);
    • The period of time during which the situation applied (i.e. the period of time during which they had a "history of glandular fever" (i.e. a period of time from when they first had glandular fever with no upper bound or extending until death);
    • The time during an episode of care when the situation was recognized (i.e. a period starting when "history of glandular fever" was first recorded as part of the record of this episode of care);
    • The time during which the situation was considered clinically relevant (i.e. a period of time based on a clinical judgment of the significance of a past history of glandular fever to the currents longer term health).

2.2.13.2

The following rules clarify the impact of [ 408731000 | temporal context ] on interpretation of HL7 data and time attributes associated with an Act class instance.

1. If a SNOMED CT expression includes an explicit [ 408731000 | temporal context ] value, the effectiveTime SHALL be interpreted as applying to the time at which the focus concept applied.
   • The focus concept is the value of the [ 246090004 | associated finding ] or [ 363589002 | associated procedure ] in the SNOMED CT expression or concept definition.
     • For example, the Act.effectiveTime for [ 407553003 | history of - glandular fever ] is the time, in the past, when they had glandular fever.
   • If the [ 408729009 | finding context ] indicates negation (e.g. [ 408729009 | finding context | = 410516002 | known absent ]), the Act.effectiveTime refers to the point in time or period or time during which the focus concept was known to be absent
   • Similarly, if the [ 408730004 | procedure context ] has a negative value such as [ 3385660001 | not done ] the Act.effectiveTime refers to the point in time or period or time during which the focus concept was not done.
     • For example, the Act.effectiveTime for [ 165139002 | endoscopy not carried out ] represents the time at which, or period during which, an endoscopy was not done.
3. If the SNOMED CT expression in an Act class instance specifies [ 408731000 | temporal context | = ([ 410584005 | current - specified |) OR ( 410587003 | past - specified )]:
   • the Act.effectiveTime attribute SHALL be present and its value SHALL be interpreted as the clinically relevant point or period in time at which the focus concept applied or is intended to apply.
5. If the SNOMED CT expression in an Act class instance does not explicitly specify [ 408731000 | temporal context ] or explicitly specifies [ 408731000 | temporal context | = ( 410512000 | current or specified | ) OR ( 15240007 | current | ) OR ([ 410585006 | current - unspecified |)]:
   • the Act.effectiveTime attribute SHOULD be included and, if present, its value SHALL be interpreted as the clinically relevant point in time or period during which the associated finding procedure applied or is intended to apply.
     • If the Act.effectiveTime represents a period of time with an upper bound either set in the future or omitted, this indicates that the focus concept continues (or is expected to continue) to apply beyond the time when it was recorded.
   • If the Act.effectiveTime attribute is omitted (or contains a null flavor), the Participation.time value stated for a performer MAY be regarded as an approximation to the clinically relevant time.
7. If the SNOMED CT expression in an Act class explicitly specifies [ 408731000 | temporal context = ((410513005 | past |) OR ( 6493001 | recent |))]:
   • the Act.effectiveTime attribute MAY be included and, if present, its value SHALL be interpreted as the clinically relevant point or period in time to which the focus concept applied or is intended to apply.
   • the Participation.time value stated for an author SHALL be regarded as the time at which it was asserted that this procedure or observation was carried out in the past.
9. If the SNOMED CT expression in an Act class instance explicitly specifies [ 408731000 | temporal context | = 410588008 | past - unspecified ]:
   • the Act.effectiveTime attribute SHALL NOT be included as this would contradict the asserted [ 408731000 | temporal context ].
   • the Participation.time value stated for an author SHALL be interpreted as the time at which it was asserted that this procedure or observation was carried out in the past.
11. If the SNOMED CT expression in an Act class explicitly specifies [ 408731000 | temporal context | = 410589000 | all times past ]:
    • the Act.effectiveTime attribute SHOULD NOT be included but, if present, it SHALL only specify the upper bound of a period of time.
      • Note: The [ 408731000 | temporal context | = 410589000 | all times past ] is used with [ 408729009 | finding context | = 410516002 | known absent ] to assert a negative past history or a negative family history (e.g. [ 266882009 | no family history or ischemic heart disease ]). Negative assertions of this type imply that at [ 410589000 | all times past ] the focus concept did not apply. It is reasonable to combine this with the upper bound of a period of time, as the finding may be true at some future point in time (e.g. the patient may now be diagnosed as having asthma, although they have no past history of asthma). However, it would be contradictory to specify a point in time value or a lower bound for a period of time.
    • the Participation.time value stated for an author SHALL be interpreted as the time at which it was asserted that at all times past this Observation applied.

2.2.13.3

In most cases, following the general rules specified by the HL7 RIM allow unequivocal interpretation of the meaning of the Act.effectiveTime and associated Participation.time values. However, there are several possible interpretations of Act.effectiveTime, in relation to a SNOMED CT expression which includes an explicit past history temporal context (i.e. [ 408731000 | temporal context << 410513005 | past ]). Therefore, the rules specified above require that the relative time as specified by the SNOMED CT [ 408731000 | temporal context ] and any specific point or period of time expressed in Act.effectiveTime should be consistent with one another. The rules do not permit the effectiveTime and [ 408731000 | temporal context ] to be interpreted in a combinatorially manner. Thus if the [ 408731000 | temporal context | = 410513005 | past ] the Act.effectiveTime, if stated, must be the point or period in the past when the finding applied.