American Association for Clinical Chemistry
Better health through laboratory medicine
NACB - Scientific Shorts
NACB - Scientific Shorts (formerly NACB Blog)
By Pamela Banning, MT(ASCP)cm, PMP

We are often asked if the same LOINC® code indicates identical tests. This is a very relevant communications issue for achieving interoperability and meaningful use among laboratories, healthcare providers, and health information exchanges. It is important for the industry to understand that LOINC® does not replace all supporting identification of a laboratory assay.  LOINC® is a universal identifier to be used in HL7 messaging, embedded alongside the local laboratory’s mnemonic, display name, units of measure, reference range, and interpretative data.  The systems should not be asking the LOINC® code to carry the full burden of identification for every regard.

So, as two paths theoretically converge on one side of an interoperability bridge and they need to merge in order to cross, what perspectives are brought along? On the laboratory path, there is a catalog of laboratory tests created by the needs of the providers it serves. They are vetted and investigated by the Medical Director or Pathologist.  Their accuracy and precision are inferred by best practices acknowledged through laboratory accreditations by credentialing agencies.  Some assays additionally are continually participating in external quality assurance programs.  These ongoing processes weigh heavily on the Director’s minds when asked to adopt a harmonizing coding set for sharing lab values with other systems. This shapes their perspectives and expectations of what LOINC® will do.
On the LOINC® coding path, there is a method of evaluating each chartable result field in the laboratory information system (LIS) in which six attributes are used to  “measure up” the assays for identifying a numeric code: component/analyte, property, timing, system, scale and method.  The laboratory domains covered in LOINC® include chemistry, hematology, coagulation, urinalysis, blood bank, microbiology, virology, cytopathology, pathology, molecular pathology, genetics and more. Components include proteins, enzymes, hormones, cellular morphology, therapeutic drugs, antibiotics, etc.   If the assay’s display is only a genus /species name, the LOINC® component evaluation goes further down to the level of organism entity, organism DNA, organism rRNA, IgG or IgM antibody against the organism.  The answer format of each assay is influenced by the abilities/limitations of the kit or instrumentation.  Review of kit packages, reagent or instrumentation documentation along with acceptable specimen types and examination of the actual result entry options will determine the remaining attributes. Answers such as “negative” or “negative <1:20” have different property attributes, and thus have different codes. Units of measure of “mg/dL” and “mmol/L” will have different property attributes and also different LOINC® codes. LOINC® is useful for both identifying similarities and dissimilarities between assays. 
The LOINC® User’s Guide Preface (entire guide available at provides examples where “the exchange and pooling of results, such as blood hemoglobin, serum potassium, or vital signs, for clinical care, outcomes management, and research” are facilitated by adoption of the vocabulary standard.  A further example of the theoretical bridge crossing: consider a pilot statewide health information exchange project performed several years ago.  Along the laboratory path came 14,802 local result fields from five test catalogs at unrelated hospital enterprises.  They were mapped to LOINC®, and in the process of crossing the bridge distilled down to 4,051 distinct concepts.  From a viewport of finding identical assays, the team found:
• 25% of the codes had three or more labs reporting the same test/specimen/result format. 
• 23% of the codes were identical reporting formats used by two labs. 
•  52% of the codes were distinct formats across the five catalogs.
From a dissimilarity viewpoint, the team determined ‘Lyme Disease Antibody’ was not the same as ‘Lyme Disease Serology’ from another lab.  [The former was a Borrelia burgdorferi antibody IgM by Western blot, while the latter was a B. burgdorferi antibody IgG titer.]
In order to answer today’s topic question it is necessary to have the right use case in mind. For the purposes of allowing the data stream of verified answers converge from different originating laboratories and have the software automatically manage storage of similar results, they are identical.  The messages retain all information that came from the performing labs for the clinician to have when interpreting the results, and thus retain the units of measure, reference ranges, footnotes, etc.   The assays may not be identical when examining the kit/reagent/instrument they are run on, cost per test, assay calibration, or their CPT codes (which is an entirely different story).  LOINC® coding does not incorporate any of these data elements into the vocabulary standard; thus is not intended as a comparison basis for those use cases.
In conclusion, this blog entry provided the context to view LOINC® codes when comparing tests for downstream collation amongst different facilities. Looking forward to further discussions! 

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Posted by D. Panton
On 6/23/2012

We have rec'd the codes for our send outs from Quest. It took a while for our rep to get them. Will we need to get the in house codes from each vendor? Each rep is still confused at this point. When will have to have the codes in the CDM so they are embedded in the billing?


Posted by Pamela Banning
On 6/27/2012

Thank you for your comment; most of the national send out labs post the LOINC codes in spreadsheet form on their websites. On the kit and instrument front some vendors already post them in the User's Group section of their website (Roche is an example). There is an IICC effort to get vendors to post LOINC codes out on (as reported at a past LOINC meeting). It's becoming apparent that as a corporation performs the work internal communications needs to be addressed to all the reps and public contacts to diffuse the confusion. Having codes in the content data management system for billing purposes appears to be a provider/payer issue which would have an effective date between those entities. There are training classes and tutorials available for laboratories who take a proactive stance and map from their LIS set up. Visit for the 24/7 slideshow tutorial as well as a listing of trainings by CAP/AHA across the country. There will also be a brown bag tutorial at AACC Annual meeting this summer.