Same lab/drug (labevents, chartevents) should be under same concepts

[sunbiz]

To avoid duplicates through distinct itemid, we are able to import fewer obs because concepts that have similar names in prescriptions, labevents, and chartevents have different itemid in d_items and d_labitems.

e.g. SELECT * FROM mimic4.d_labitems l, mimic4.d_items i where l.label LIKE i.label; produces Hemoglobin with 4 different itemid that should refer to the same concept.

One approach could be create a mapping CSV that links all d_labitems.itemid to d_items.itemid and creates only one concept, for which obs.concept_id is the same, even if the obs came from chartevents, labevents, prescription or elsewhere.