Which code is used for the initial OATS visit?

• A. G8539
• B. G8542
• C. G8942
• D. GP modifier

Answer: (A)

The key idea is that the first encounter within a program is billed with a specific code that marks it as the initial visit. For the initial OATS visit, the designated code is G8539. This code is chosen to capture the intake and initial assessment of the patient within the OATS protocol, clearly differentiating it from later visits that may be billed with different codes or modifiers. The other options don’t fit because they refer to either different services or a modifier rather than the initial encounter itself—the GP modifier is not a standalone visit code.