ACSN subsumes LACSN (See FHIR-37739) and is in the value set IdentifierType. So, for laboratory accession numbers ACSN would be the appropriate code to send and LACSN could also be sent if desired.
I suggest that LACSN be removed from the list of values for Identifier.type in AU Accession Number. Its correct use is complex and it offers little value.
The profile AU Accession Number requires the use of one of two values for Identifier.type: ACSN and LACSN from http://terminology.hl7.org/CodeSystem/v2-0203.
ACSN subsumes LACSN (See FHIR-37739) and is in the value set IdentifierType. So, for laboratory accession numbers ACSN would be the appropriate code to send and LACSN could also be sent if desired.
I suggest that LACSN be removed from the list of values for Identifier.type in AU Accession Number. Its correct use is complex and it offers little value.