Providers are reminded that retroactively effective for dates of service on or after September 1, 2006, CPT-4 code 87900 (infectious agent drug susceptibility phenotype prediction using regularly updated genotypic bioinformatics) is not separately reimbursable with codes 87903 (infectious agent phenotype analysis by nucleic acid, [DNA or RNA] with drug resistance tissue culture analysis, HIV 1; first through 10 drugs tested) and 87904 (each additional drug tested).