Free Text Sig
Discord is afoot. It has been for some time now. The cause is a little understood data element known as “Free Text Sig”.
Way back in history, the Healthcare Information Technology Standards Panel (HITSP) was tasked to find a place to store the free text instructions a clinician writes when prescribing a medication (known typically as the free text sig). Keith Boone was there, and his blog will certainly provide more history than mine, but my understanding is that HITSP looked at what was available in Clinical Data Architecture (CDA), and decided that substanceAdministration/text met the use case, because that element is supposed to contain the textual representation of all the information in the substanceAdministration template (i.e. the free text sig and more). So HITSP labeled substanceAdministration/text as “Free Text Sig”.
…and so the trouble began.
The problematic HITSP “Free Text Sig” label was grand-fathered into the Consolidated Clinical Data Architecture (C-CDA). Implementers, however, have misunderstood the label, and assuming the free text sig, and only the free text sig, should appear in substanceAdministration/text. In practice, the free text sig is not meant to include the medication name and other items. Implementers look at the RIM definition and include everything from the substanceAdministration act. Complicating matters, some receiving systems (it’s unclear how many) want to process the free text sig as discrete information, and given the inconsistency of substanceAdministration/text, they can’t rely on it.
To make matters worse, a Draft Standard for Trial Use (DSTU) comment asked for clarification from C-CDA, and the Structured Documents Working Group (SDWG) stated that substanceAdministration/text is the wrong place to put the free text sig. The SDWG considered reversing this decision, staying with the HITSP ruling, but this would not address the confusion implementers have with the current free text sig. Another solution is needed if the initial SDWG decision is unacceptable.
The latest free sig discussion took place on the SDWG call on October 16, 2014. The loose consensus is that substanceAdministration/text is damaged goods , and a clear, unambiguous place to store free text sig should be defined for those who wish to exchange it. Keith and I agreed to hash out a solution. Here is my first cut:
- Create a new template that is related to the medication activity template via an entryRelationship where @typeCode=”COMP”.
- Call it the full text sig.
- Have it only contain a LOINC code and substanceAdministration/text (consumable and everything below would be nullFlavor=”NA”).
- This gives implementers an unambiguous place to just put the SIG, and nothing else.
Here is what the proposed template would look like.
<substanceAdministration classCode=”SBADM” moodCode=”EVN”>
<templateId root=”FULL-TEXT-SIG-TEMPLATE-ID” extension=”DATE”/>
<text>twice daily with food, except when something weird happens.</text>
The actual template ids and LOINC codes are yet to be defined, and the example above includes placeholders.
The SDWG will discuss this on the teleconference on October 21, so I doubt this solution or Keith’s will be the final word, but it’s a start.