The Carrier claims file was originally called the Physician/Supplier Part B file. This file contains final action claims data submitted by non-institutional providers. These claims are largely from physicians, although they also include claims from other non‐institutional providers such as: physician assistants, clinical social workers, nurse practitioners, independent clinical laboratories, ambulance providers, and free‐standing ambulatory surgical centers. Each record in the Carrier claims file is a claim.
Each carrier claim must include at least one Health Care Procedure Classification Code (HCPCS code) to describe the nature of the billed service. Each HCPCS code on the carrier bill must be accompanied by a line item ICD-9 diagnosis code, providing a reason for the service. In addition, each line item has the fields for the dates of service, reimbursement amount, provider numbers (e.g., NPI), and beneficiary demographic data. Each claim is comprised of up to 13 line items, each of which corresponds to one HCPCS code and its accompanying information.
The most important aspects of the CMS BSA Carrier Line Items PUF 2010 are that it contains carrier line item services for a simple random sample of 5% of the 2010 beneficiary population. Out of approximately 2.5 million beneficiaries in the 5% sample, 1,596,468 had claims, resulting in a PUF of 70,052,393 line items after excluding invalid line items, denied claims and protecting the privacy of Medicare beneficiaries. The line item payments have been rounded and the ICD‐9‐CM diagnosis codes have been coarsened in order to protect individuals from identification while retaining the analytic value of the data. A line item service for a sampled beneficiary is only included in the PUF if the combination of all ten variables is shared by at least eleven line items pertaining to at least eleven beneficiaries and eleven providers in the population. For some combinations of values of the ten variables, however, there are fewer than eleven line items in the PUF. Line items cannot be linked by claim or by beneficiary, and cannot be linked to any external data source by means of the carrier line ID. The carrier line ID is a cryptographic key specific to the CMS 2010 BSA Carrier Line Items PUF and not available elsewhere. The CMS 2010 BSA Carrier Line Items PUF is sorted by this carrier line ID to ensure that the relative positions of each line item in the PUF and in the original source data are totally uncorrelated.