G0399-Home sleep test (HST) with type III portable monitor, unattended, has a PC/TC Indicator of 1, meaning the code has a technical & professional component. G0399 can be bill for the global services without a modifier or can be billed for the technical component only using modifier TC (G0399-TC) and for the professional component only with modifier 26 (G0399-26)
So, it would be inappropriate to bill G0399, which is the global procedure for this service, followed by 95806-26 for the professional component of a sleep study. You would be double dipping on the professional component because G0399 billed without a modifier is the global billing which includes the technical and professional component and then billing 95806-26 is billing a second time for the professional component of an unattended sleep study.
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