Indicates that the decision to substitute or to not substitute was driven by a desire to maintain consistency with a pre-existing therapy. I.e. The performer provided the same item/service as had been previously provided rather than providing exactly what was ordered, or rather than substituting with a lower-cost equivalent.

Indicates that the decision to substitute or to not substitute was driven by a policy expressed within the formulary.

In the case of 'substitution', indicates that the substitution occurred because the ordered item was not in stock. In the case of 'no substitution', indicates that a cheaper equivalent was not substituted because it was not in stock.

Indicates that the decision to substitute or to not substitute was driven by a jurisdictional regulatory requirement mandating or prohibiting substitution.