Billing and Coding: In Vitro Chemosensitivity & Chemoresistance Assays

This billing/coding guidance clarifies claim modifiers and ABN handling for in vitro chemosensitivity and chemoresistance assays. Claims must include the appropriate CPT code to receive a CSRA denial; statutorily excluded services do not require an ABN and should be indicated with modifier GY, while a voluntary ABN should be indicated with modifier GX.

"Statutorily excluded services for in vitro chemosensitivity/chemoresistance assays do not require an Advance Beneficiary Notice (ABN)."

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