Answer: Antigen coding has allergy coders tearing their hair out as they try to nail down the dose/unit per vial regulations. But even though carriers have different interpretations of how many doses/units per vial are billable on one DOS, all carriers agree that it is the number of doses/units in each vial that determines coding and billing methods, not the number of antigens that a vial contains. In other words, you would code and bill 95165 times the total number of doses, which in your prescribed scenario would be 40 because there are four vials of 10 doses. When the patient comes to the office for the injections, you should bill 95117 (Professional services for allergen immunotherapy not including provision of allergenic extracts; two or more injections).
The first clue that should signal to you how to code for antigens can be found in the definition of procedure code 95165: "Professional services for the supervision of preparation and provision of antigens for allergen immunotherapy; single or multiple antigens (specify number of doses)." The definition clearly states that the number of antigens is irrelevant. CPT 2002 also specifies for coders that "a dose is the amount of antigen(s) administered in a single injection from a multiple-dose vial."
Empire Medicare Services' antigen LMRP does a good job of clarifying how they, and most Medicare carriers, view doses/units when billing for antigen injections: "A dose is now defined as a one (1) cc aliquot (sample) from a single multidose vial. When billing 95165, providers should report the number of units representing the number of 1-cc doses being prepared. A maximum of 10 doses per vial is allowed for Medicare billing, even if more than 10 doses are obtained from the vial. Medicare should not be billed an additional amount of these diluted doses under code 95165."
The only circumstance that would require you to bill 95165 x 4 would be if there were four one-dose vials, which is rarely done because of the cost of supplies.
