This case-sensitive code system http://hl7.org/fhir/us/cdmh/CodeSystem/pcornet-lab-loinc-source-codes defines the following codes:

Code	Display	Definition
IN	Instrument	Assigned by the instrument used to process the sample and generate the result.
LM	LIMS (Standalone or EHR)	Code is assigned by the system used to manage laboratory results, either stand-alone or as part of the EHR.
HL	HL7 feed or other interface	Code is assigned from an external HL7 feed or other interface (e.g., by a Health Information Exchange).
DW	Data warehouse	LOINC codes are generated during the extract-transform-load (ETL) procedures used to populate a standalone data warehouse or reporting database.
PC	PCORnet ETL	LOINC codes are assigned as part of the ETL process used to populate the PCORnet CDM.
DM	Other CDM	Codes are assigned through the ETL used to populate a CDM that is upstream from the PCORnet ETL.
NI	No information	Source/provenance of the LOINC code for this result has No information.
UN	Unknown	Source/provenance of the LOINC code for this result is Unknown.
OT	Other	Source/provenance of the LOINC code for this result is Other.