Billing and Coding: In Vitro Chemosensitivity & Chemoresistance Assays

In vitro chemosensitivity and chemoresistance assays are statutorily excluded from Medicare coverage under LCD L37630 (not covered). For billing, submit the appropriate CPT code to obtain a CSRA denial, append modifier GY to indicate a statutorily excluded service (an ABN is not required) and append modifier GX only when a voluntary ABN is issued.