According to the specification, SVC06 is required when "the adjudicated procedure code" is different than the "submitted procedure code". If a modifier is changed, or added or deleted, and the procedure code did not change, is SVC06 required? Since this is a composite field and contains both procedure code and modifier codes, it would support this functionality. But the situational note does not explicity state that a change to modifier makes the field required.
This issue is explicitly addressed in guide 005010X221. The situational rule on SVC06 reads "Required when the adjudicated procedure code provided in SVC01 is different from the submitted procedure code from the original claim." That statement ties all of SVC06 to SVC01, not just specific component elements of the composites. Changes to the modifiers therefore represents changes to the procedure code as identified in the composite as a whole.