LOINC and the SDTM


LOINC is a pre-coordinated laboratory coding system used in healthcare IT systems. It includes lab tests, clinical measures, HIPAA documents and standardized survey instruments. It also contains terms for human clinical research but its scope goes beyond research use. LOINC is used in over 170 countries and is mandated in 30. LOINC is maintained by Regenstrief Institute, INC and is supported by the US National Library of Medicine (NLM). LOINC describes observations using the six components in the table below. Note: these six components do not translate directly to SDTM variables.


LOINC: Components of 1 Code LOINC: Component Description LOINC: Example(13986-5) CDISC: Mapping is to Multiple SDTM Variables
Component Analyte - The substance or entity being measured or observed. Albumin/Protein.total --TEST and --TESTCD
Property The dimension of the analyte observation value. Mfr (Mass Fraction) Not an SDTM variable, can be deduced from result unit
Time The point in time or interval of time over which an observation or assessment was made. 24H Timing Variables e.g., --DTC and, for intervals, --ENDTC
System The specimen or entity upon which the observation was made. Urine --SPEC; --LOC
Scale Result type; How the observation value is expressed (e.g., quantitative, ordinal, nominal). Quantitation Not an SDTM variable, can be deduced from result
Method Assay Method; high-level description for how the measurement or assessment was performed. Electrophoresis --METHOD and sometimes --ANMETH and/or --TSTDTL
Note: one LOINC code maps to many CDISC variables
Using LOINC in Clinical Research
  • LOINC codes are NOT required by CDISC standards
  • LOINC codes ARE required by some regulators for regulatory submissions (e.g., US FDA as of Mar 2020)
  • LOINC codes ARE required in some countries for healthcare IT systems 

Use LOINC codes supplied by the analytical lab where applicable and available.

The US FDA recognizes that not all tests have LOINC terms.  For those that don’t, or where analysis is done by small specialty labs that do not have the facility to provide them, the codes may be omitted and explained in the SDRG, but the FDA does expect that some effort be made to obtain them.

US FDA/CDISC/Regenstrief/NIH LOINC Working Group is addressing implementation concerns and has published recommendations for submission of LOINC codes.

The US FDA Standards Website states that “…The FDA plans to review the Working Group document and provide recommendations in the Study Data Technical Conformance Guide.”


CDISC Actions

CDISC SDTM findings domains can use the standard variable LOINC.

CDISC is preparing mappings of common LOINC codes to SDTMIG variable values

Further Reading

Recommendations for the Submission of LOINC® Codes in Regulatory Applications to the U.S. Food and Drug Administration, November 2018

LOINC Getting Started Guide

LOINC Overview Video

LOINC and RELMA Workshops

LOINC Essentials eBook -  Covers the basics of LOINC and specific mapping strategies: