We are a group audiologists who provide newborn hearing screenings in several hospitals before the infant is discharged. Some payers include our services in the DRG even though we are not employed by the facility nor do we use any of their staff, equipment or supplies. Do we have to use POS 21 for inpatient hospital, or can we use POS 81 for a laboratory certified to perform diagnostic and/or clinical tests independent of an institution or physicians office? Some providers are using the POS 81 and being reimbursed by the same payers that include our services in the DRG.