The guidelines require the pathologist/laboratories to clearly document when a multiplex/ cocktail stained probe procedure has been performed for FISH. Unit of service for FISH is “per specimen, per separate single probe stain procedure.”
Note that CPT 88364 has a + sign denoting it is an add on code and can only be billed when CPT 88365 is also billed. CPT 88364 is for each additional probe “stain procedure” for a different antibody(s). Also note that the add on code in this instance is before the primary procedure code in number. AMA didn’t have an available code in this area to make the add on code come after the primary code in number like they normally do. So coders will have to pay CLOSE attention to make sure they don’t bill the wrong code as the primary and add on code.
CPT 88366 represent multiplex antibody probe stain procedure and is introduced to represent when a single probe stain procedure contains multiple antibodies on that given probe.
CPT Codes For Surgical Pathology In Situ Hybridization
Description of CPT 88364:
In situ hybridization (eg, FISH), per specimen; each additional single probe stain
procedure (List separately in addition to code for primary procedure).
Use CPT 88364 in conjunction with CPT 88365.
Description of CPT 88366: In situ hybridization (eg, FISH), per specimen; each multiplex probe stain procedure.