Act.negationInd

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2.2.9

The Act.negationInd is defined by HL7 as “An indicator specifying that the Act statement is a negation of the Act as described by the descriptive attributes”.


2.2.9.1

The semantics of this attribute overlaps with:


  • SNOMED “[ 408729009 | finding context ]” values indicating absence of a specified finding.
  • SNOMED CT “[ 408730004 | procedure context ]” values indicating that a specified procedure was not done.

This overlap leads to a potential ambiguity since a combination of negationInd with a contextual representation of absence might be interpreted either as:


  • double negation (i.e. "finding X is not absent" which is equivalent to "finding X is present")
  • restatement or emphasis of the negative resulting from a mapping between the two ways to indicate negation or absence (i.e. "negative observation: finding X is absent" which means "finding X is absent").
2.2.9.2

The following rules avoid the risk of misinterpretation by prohibiting use of the negationInd in Act class instances that are encoded using SNOMED CT.


  1. In a constrained information model or template the negationInd attribute SHOULD be omitted from:
    • any Act class clone in which SNOMED CT is the only permitted code system for the Act.code attribute.
    • any Observation class clone in which SNOMED CT is the only permitted code system for the Observation.value attribute.
  2. In a constrained information model or template, the negationInd attribute SHALL be optional if it is included in:
    • an Act class clone in which SNOMED CT is one of the permitted code systems for the Act.code attribute.
    • any Observation class clone in which SNOMED CT is one of the permitted code systems for the Observation.value attribute.
  3. The negationInd attribute SHOULD be omitted from any Act class instance in which the Act.code attribute is expressed using SNOMED CT.
    • Negative assertions about an Act (e.g. "procedure not done", "substance not to be administered" ) SHOULD be represented, as part of the SNOMED CT expression in the Act.code attribute, by including the appropriate explicit [ 408730004 | procedure context ] (e.g. [ 3385660001 | not done ] or [410521004 | not to be done]).
  4. The negationInd attribute SHOULD be omitted from any Observation class instance in which the Observation.value attribute is expressed using SNOMED CT.
    • Assertions of negative Observations (e.g. absence of a specified finding) SHOULD be represented, as part of the SNOMED CT expression in the Observation.value attribute, by including the appropriate explicit [ 408729009 | finding context ].
  5. The negationInd attribute MAY be included in an Act class instance where the SNOMED CT expression represents a [ <<71388002 | procedure ] with no explicit [ 408730004 | procedure context ] or a [ <<129125009 | procedure with explicit context ] with [ 408730004 | procedure context | = 385658003 | done ]
    • This approach is not recommended but is permitted to allow simple negation in systems that do not support the SNOMED CT context model. If it is used, it SHALL be interpreted as equivalent to the specified [ 363589002 | associated procedure ] with [ 408730004 | procedure context | = 3385660001 | not done ].
  6. The negationInd attribute MAY be included in an Observation class instance where the SNOMED CT expression represents a [ <<404684003 | clinical finding ] with no explicit [ 408729009 | finding context ] or a [ <<413350009 | finding with explicit context ] with the [ 408729009 | finding context = 410515003 | known present ].
    • This approach is not recommended but is permitted to allow simple negation in systems that do not support the SNOMED CT context model. If it is used, it SHALL be interpreted as equivalent to the specified [ 246090004 | associated finding ] with a [ 408729009 | finding context | = 410516002 | known absent ].
  7. If the negationInd attribute is present in an Act class instance in which either the Act.code or Observation.value is expressed using SNOMED CT, it SHALL be interpreted as an error unless the conditions noted in points 5 and 6 above apply.
2.2.9.3

The Act.negationInd is an optional RIM attribute which negates the meaning of an Act. This negation is unnecessary in cases where SNOMED CT is used because the context attributes can be used to specify the absence of a finding or the fact that a procedure has not been done. Including both representations introduces potential for serious misinterpretation of combinations including the following:


  • Double negative
    • If negationInd is true and the SNOMED CT [ 408729009 | finding context | = 410516002 | known absent ] the double negative would be “not known absent” (i.e. “present”).
    • If negationInd is true and the SNOMED CT [ 408730004 | procedure context | = 3385660001 | not done ] the double negative would be “not not done” (i.e. “done”).
    • For the avoidance of potential ambiguity this option is explicitly prohibited by rules in this document.
  • Indication or emphasis of negation
    • HL7 negationInd indicates the presence of negation and the SNOMED CT context provides more details of the nature of the negation.
    • Implies that if negationInd is true and the Act is coded with SNOMED CT an appropriate negated SNOMED CT finding or procedure context value (e.g. [ 410516002 | known absent ] or [ 3385660001 | not done ]) should also apply.
    • Might imply that if a negated SNOMED CT finding or procedure context value (e.g. [ 410516002 | known absent ] or [ 3385660001 | not done ]) is applied the negationInd should be true.
  • Restatement of negation
    • HL7 negationInd and SNOMED CT negative contexts apply as alternatives and when combined serve to restate the negation
    • Implies that if only negationInd is present a mapping table is required to the relevant SNOMED CT context to enable consistent interpretation. This mapping table would need to specify combinations of moodCode and negationInd. For example, negationInd=true with moodCode=“EVN” the would imply [ 408730004 | procedure context | = 385660001 | not done ], whereas negationInd=true with moodCode=“RQO” might imply [ 408730004 | procedure context | = 410521004 | not to be done ].

The simplest way to avoid these possible misunderstandings is to omit the negationInd attribute and allow the SNOMED CT context attributes to provide information about absent findings and procedures that have not been done. However, to meet requirements to support some simple negation in systems that do not support the SNOMED CT context model, use of negationInd is permitted where it cannot be misinterpreted . The only cases where no risk of misinterpretation are where the SNOMED CT context is either unspecified or explicitly states the default values [ 410515003 | known present ] or [ 385658003 | done ]. The negationInd can be used to switch these defaults to the appropriate negated values such as [ 410516002 | known absent ] and [ 385660001 | not done ].


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