TOP 2000+ common US lab

Hi Everyone!

I have questions on some LOINC that made it to the top ranks but others with same format didnt make it. For example,

<span style=“text-decoration: underline;”>32515-9 CD3+​CD4+​ (T4 helper) cells [#/​volume] in Unspecified specime</span>n is rank 602. But with the same format,

<span style=“text-decoration: underline;”>32517-5 CD3+CD8+ (T8 suppressor cells) cells [#/volume] in Unspecified specimen</span> is not ranked. My problem is I assume that most cd4 and cd8 absolute ct are run on BLOOD as spx. But after seeing 32515-9 as ranked, made me cautious to check if “blood” is stated as the specimen for abs cd4+, or else map it to 32515-9. Doing that, I should be cautious as well with cd8 with unspecified specimen? the problem is that 32517-5 is not rank but “blood” as specimen is (14135-8 CD3+CD8+ (T8 suppressor cells) cells [#/volume] in Blood).

This also happens with other LOINC such as:

Erythrocytes [Presence] in Urine (ranked)

Leukocytes [Presence] in Urine (not ranked)


We totally avoid using unranked codes unless the result specified a method or sub-component that would affect the interpretation of the result. Other than that, I hope to get a response on this since we are having trouble on why some ranked codes didnt make it to the top and some does but with the counterpart not making it such as my examples.

Hi Ramel,

The Top 2000+ common US lab file was recently discussed at the December 2018 Laboratory LOINC Committee meeting. While Regenstrief was thinking of retiring the 10 year old file for it had accomplished their expectation for that moment in time in gaining more LOINC adoption, it became apparent that a variety of non-hospital venues were using the file for other use cases in 2018. Regenstrief opened the possibility of readdressing and updating the file, without a priority timeline.

Please be aware that the file was created based on the adopters at that time who volunteered to submit their mappings for the contribution. Analysis took place across the contributed files. Different mapping styles and content are brought in side for side to identify the top 2000. Not all laboratory information systems are built with the same content or result fields.

I would suggest once your team is confident in mapping your specific content, that the requirement to only utilize ranked items is dropped. The LOINC database is rich for many possibilities of LOINCing styles. Once you identify the pattern of mappings your site needs, follow them.

Let me know if you have any questions, Happy LOINCing!

Pam Banning