Serology performed on plasma samples

In our laboratory infectious disease serology testing. ie Hepatitis antibodies, is preferentially performed in serum samples. Occasionally a serum sample is not available and the test is performed on an available plasma sample. Since the material ‘serum’ is specified in the system axsis, the regular LOINC code would not cover this test as it is performed in a different material. The results are rapported on a single line in the hospital information system and based on the properties of the test there will not be big differences in tests performed in serum vs plasma.

What LOINC code should we use for reporting serology test performed on plasma samples and wat is the background/argumentation for only specifying ‘Ser’ in the system axis on serology tests?

Do we need te request new LOINC codes for serology tests in plasma? Preferably not since this would lead to a large amount of new code requests.

We have a similar issue in veterinary medicine. We have a number of serologic tests that were designed to be run on serum. Because serum is often difficult or impossible to obtain, some of these have been validated for other specimens such as oral fluid or “meat juice” (fluid from a frozen and thawed muscle sample). Because we are trying to get away from XXX as a specimen type, we would really like a specimen type of “Serum or appropriate substitute.” This would be much more precise than simply saying “Body fluid” but wouldn’t make it seem wrong to use a “Serum” LOINC code with a substitute.

For the original posting, please refer to page 25 in the LOINC User’s Manual. If it’s determined that an assay can equivocally be run on serum or plasma, Regenstrief is asking for notification on the serum LOINC code to be updated to SER/PLAS in the next release. You could start wth a email, but they may ask for it via RELMA submission. In the daily routine, remember to use the SPM segment of the HL7 message to accurately record the true specimen being run.

This doesn’t address the veterinary situation, where the specimen isn’t entirely from the circulatory system.

Please note this Forum hasn’t traditionally been used to record additions or change requests of actual codes. I would encourage the user to make a submission of one assay with the specimen issue, include all possible links of information to get the solid research documentation. Regenstrief does individually acknowledge submissons made through RELMA. I hope that will get the ball rolling.

Have a great day!


The Ser/Plas case makes sense. I shouldn’t have tacked my issue to that one. Sorry.

I wasn’t ready to submit a request for our “weird” veterinary use case. I really wanted to see if I could get some discussion about the alternatives. As stated on pg 26

We will likely argue for either adding a distinct code for the dominantly common specimen (e.g. Stool for ameba histolytica) or the specimen prescribed by the package insert, or for entertaining a new specimen code broader than those now available but narrower than XXX to accommodate a particular need, e.g. sterile body fluid, or Genital/anal/throat (for STD specimens). This will, of course, take time and discussion.

I'm torn between asking for a new System Type for "Meat Juice" (we aren't even sure how to SNOMED code that one) and then test codes with "Ser/Oral Fluid/Meat Juice; asking for a new System Type something like "Serum Substitute" (yuck) and "Ser/Serum Substitute"; or just saying the test is based on serum and we allow the use of those substitutes. In any case, these tests can all be hidden behind "veterinary:true".

At this point, I think the least "ugly" but also least "pure" approach would be the last one; we just use the Ser codes even with the weird substitutes.