When mapping, I like to keep in mind that the healthcare provider is asking their local laboratory to “give them the battery produced by the usual methods”. This wording is coming from the LOINC Manual, June 2012, page 80. As we go through the a local laboratory catalog for the hematology profiles, we may not find all six of the CBC panels recorded in LOINC, but we’ll find a subset of a hemogram, a CBC with automated diff, and maybe one that reflexes a CBC to a manual diff.
When we map through a client’s catalog at the results level, we’ll find a field for nucleated RBCs. While not always found in a patient’s hematology profile, the lab has a protocol to report them. Thus, while it appears in a flat extracted file that nucleated RBCs are always a part of a panel, I would suggest that they are provided a place to be reported when encountered.
When choosing a LOINC order code, it’s not always possible to account for every variation between laboratories in what is “produced by the usual methods”. I would give this client the closest LOINC order code, even if nucleated RBCs are not listed in RELMA currently.