FAQ: LOINC Content

Where can I find the meaning of the abbreviations (e.g. MCnc, SCnc, etc.) used in LOINC?

The LOINC Users' Guide contains much useful information, including the meanings of such abbreviations. In addition, many of these abbreviations are shown on the "View Details" screen for a given LOINC code within the RELMA program.

How do I interpret LOINC abbreviations?

Many allowable component name abbreviations are listed in the General naming conventions section of the LOINC Users' Guide.

What is the difference between mass concentration (MCnc) and substance concentration (SCnc)?

Test results with unit of measure of mass in the numerator and a volume in the denominator (like mg/dl) have mass concentration(MCnc) as the property. Test results measured with moles in the numerator and volume in the denominator (such as mmol/L) have substance concentration(SCnc) as the property. In the United States, most tests are mass concentration, with the notable exception of electrolytes. Substance concentration might be used more in Canada.

What are the LOINC codes with DNA in the name?

These are tests that use DNA and are indicated by "probe" in the method. These methods may also be used to detect RNA, especially RNA which is present in large enough quantities to detect easily with the probe.

What does the method of “calculated” mean?

“Calculated” indicates that the measurement is derived from two different variables.

Is LOINC applicable/suitable for genetic tests?

Yes, LOINC codes are created for routine genetics tests that are reported by many large national laboratories. The LOINC Users' Guide describes the strategies we use for naming these tests.

One should realize the goal for LOINC is to serve laboratory reporting of clinical data with as much structure as laboratories conventionally report. For example, in the case of routine chemistry tests most laboratories report the each discrete observation as a separate result and include a separate OBX (observation request segment of an HL7 message) for each of those separate results, each of which requires its own LOINC code. For instance, a complete blood count requires many LOINC codes to report in a fully structured form.

Unlike most laboratory reports, the majority of genetic tests are now reported as a narrative report; more like a radiology report or a visit note than the typical laboratory report. LOINC has codes for most of the common mutation analyses that are performed. However these narrative reports contain information that could be reported in much more detail as many discrete results. Some laboratories do report some very frequently ordered genetic tests in more detail for example they will report the lists of mutations tested and/or report the presence or absence of a particular mutation. So LOINC has codes for these commonly ordered items as well

HL7 has defined a very sophisticated reporting structure for genetic tests in general with a specific focus on sequencing. This is described in a document called "HL7 Version 2 Implementation Guide: Clinical Genomics; Fully LOINC-Qualified Genetic Variation Model, Release 1" that can be obtained from HL7. The reporting structure is also defined in terms of LOINC codes. But this more sophisticated approach is used by very few laboratories presently.

What does DONE, DUP, IDUP, ?, and X, W/D on my returned LOINC Completed Terms Report?

These abbreviations refer to the submitted term status with respect to its processing by Regenstrief.

  • DONE = term accepted and new code assigned.
  • DUP = submitted term already exists in LOINC database (duplicate)
  • IDUP = same term submitted twice (internal duplicated)
  • ? = question or more information required for submission
  • W/D = withdrawn by submitter
  • X = not suitable for inclusion in LOINC

How long will it take to receive my new LOINC code(s) after I send a submission?

Regenstrief has always tried to respond quickly to term submissions while balancing the review necessary for a high quality standard, and you keep giving us positive feedback about our performance on this. We can only do it, however, if the requester provides clear and comprehensive information about the new terms.

Even with complete information supporting your submission, some requests require discussion and decision by the LOINC Committee before they are completed by Regenstrief. These are requests for things like an entirely new kind of measurement or use of LOINC codes in ways not previously agreed upon by the LOINC Committee.

Typically, new LOINC codes for term submission will be provided to you within 6 to 8 weeks. All new LOINC codes sent to submitters between each public release are available on the LOINC Codes in Development for Next Release page. Prerelease LOINC codes are under development by the LOINC team and are subject to change prior to inclusion in a public release. It is possible that they may not be published in the next, or any, public release.

What is the use-case for LOINC panel terms?

In the laboratory, panels are usually created to represent tests that can or must be ordered as a package. The Electrolytes panel is mostly an example of the former, i.e. most of the constituent tests can be ordered separately or as a unit as part of a panel. On the other hand, the constituents of the blood cell differentials can only be obtained as part of the panel. You can't order the individual parts of a blood cell differential separately.

However, in both of cases there are exceptions. In the Electrolytes panel, the anion gap is an observation and cannot be ordered separately. In the blood cell differentials, the eosinophils count can be ordered separately. We try to mark LOINC codes as orderable, reportable (observation) or both, but may not always be right and have to depend upon the wisdom and common sense of laboratory people to know which is which.

Use in ordering is not the only purpose of panels. LOINC codes are also created to represent a set of tests, measurements or observations for other purposes. Two examples are survey instruments, where the instrument may be offered to patients but is only rarely ordered and the HEDIS & Quality Assurance measures where the panel serves to identify the individual tests that satisfy a given HEDIS quality standard.

More information on panels can be found in Section 7 of the LOINC Users' Guide.

Do tests with the same component and different reporting units of measure have different LOINC codes?

The units of measure are closely tied to the Property part of a LOINC term. Whether or not two tests that measure the same analyte but report different units have different LOINC codes depends primarily on whether the Property is the same. For example, serum albumin can be reported with the following units: mg/dL, g/dL, and umol/L. Measurements associated with either mg/dL or g/dL should use LOINC 1751-7 (Albumin [Mass/volume] in Serum or Plasma) because the Property being reported is mass concentration (MCnc) even if the reporting units are different. However, measurements reported as umol/L should use LOINC 54347-0 (Albumin [Moles/volume] in Serum or Plasma) because the Property being reported is substance concentration (SCnc).

Do point-of-care (POC) tests have different LOINC codes from the same test done in the central laboratory?

Point-of-care (POC) tests are those performed in close proximity to where the patient is located rather than in a central laboratory. For example, intensive care units often have their own blood gas and basic chemistry instruments that typically analyze whole blood rather than serum/plasma.

In general, there are typically different LOINC codes for POC tests compared to their central laboratory counterparts, but not in the way you might expect.

After discussion and debate, the Laboratory LOINC Committee decided in December 2005 not to make distinctions on the basis of location of testing or the uncertainty surrounding the methodology that are wrapped up in the general use of POC. So you will not see "POC" as a method distinction in LOINC names.

POC terms can often be distinguished based on the System part (e.g., Whole blood versus Ser/Plas) though. For example, LOINC 2947-0 (Sodium [Moles/volume] in Blood) represents a POC test run on a whole blood specimen, whereas 2951-2 (Sodium [Moles/volume] in Serum or Plasma) represents a test done in a routine laboratory.