There are about 60 pharmacy benefit management (PBM) companies in the United States; the largest players, which dominate the landscape, are Medco Health Solutions, Express Scripts, and Caremark. Pharmacies use the on-line systems operated by PBMs to verify health plan prescription coverage and complete the process of purchasing medicines by filing claims. The information recorded includes geographic and age information, the name and dosage of the drug, cost, and, in a few cases, an ICD-9 code signifying the underlying diagnosis. Prescription data enter a transactional system in real time;
periodically—often weekly—the transactional systems upload to a data warehouse designed to provide analytical "data mining'' services. The data warehouse, built around modern relational technology, can be made readily accessible to public health authorities; its value is limited by the inherent lag time. Coupling warehouse access with direct access to the transac-tional system feeding can, potentially, produce an up-to-the minute ability to detect and interpret trends in prescription drug activity indicative of a threat to public health.
The transactional systems receive data about prescriptions as soon as they are presented to pharmacists for filling. Several companies that run such systems have been using legacy mainframe systems to store these data, and these file-based (VSAM) systems were somewhat difficult to interface with. To modernize them and facilitate compliance with the Health Insurance Portability and Accountability Act (HIPAA), the vendors introduced relational database technology to make interfaces easier. External entities, such as those charged with public health surveillance, can obtain data from this transactional system in two ways: by receiving transactions in parallel to the transactional system or launching SQL-based queries, or by using decision-support tools, against the transactional relational database.
The Veterans' Administration (VA) maintains a PBM database that could serve as a model for a source of data relevant to biosurveillance. The VA has connected to its VISTA electronic point-of-care (POC) system, in operation at all VA medical centers, a PBM database that updates monthly, extracting information from VISTA's electronic medical records. Its function is analogous to its commercial counterparts. The database stores information on both inpatient and outpatient medications (including both intravenous and oral medications); these data are specific enough to allow analysis of dispensing patterns at aggregate and geographically discrete levels or at the level of individual patients and addresses (Veterans Administration, 2001). Variations, or spikes, in dispensing patterns may potentially be of value for detecting disease outbreaks. To ensure the timeliness of these data, the VA would have to arrange for at least daily polling from VISTA, but such polling is very feasible.
Although using PBM systems' data for biosurveillance is technically feasible, it is important to note that the companies collecting these data will require payment for access to the data, as well as to offset the costs of any software modifications required to provide this new service. Biosurveillance system operators will have to deal with ethical and legal (such as confidentiality) issues, as well.
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