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Introduced in Core i2b2 Version 1.6


In Version 1.6 of i2b2 we begin to use the modifier_cd column in the observation_fact table.


A CPT procedure can be modified with standard CPT modifier codes such as 62 (two surgeons) and AA (anesthesia performed personally by anesthesiologist.) 

Essentially, the modifier is a way to extend the concept code. Much of what is expressed as a modifier could be expressed by making multiple concept-modifier combinations in the concept dimension, a simple and effective approach in many cases.  However, when modifiers are associated with values (such as with dose), or can occur in many combinations (as in CPT or SNOMED modifiers,) it becomes simpler to use the modifier_cd column.