As part of the v2-to-FHIR project we are mapping commonly used fields in key v2 messages to FHIR resources so that messages can be transformed into bundle of FHIR resources. OBX-29 and 30 are the observation type and sub-type fields but there are no cognate existing data elements in FHIR. We suggest that a standard extension to Observation be created to allow exchange of these concepts.  

We suggest a complex extension that uses CodeableConcept elements using value sets http://terminology.hl7.org/CodeSystem/v2-0936 and http://terminology.hl7.org/CodeSystem/v2-0937 with a binding of Extensible.

The v2 descriptions can be reused as part of the extension narrative:

This element indicates the type of observation to enable systems to distinguish between observations sent along with an order, versus observations sent as the result to an order.

The result sub-type provides further classification of Observation Type.  This may aid in the grouping of Observations.