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Proc Annu Symp Comput Appl Med Care. 1993 : 668–672.
PMCID: PMC2850659

An Ambulatory Service Weighting System: making sense out of millions of ambulatory claims.


This paper describes a cost-based relative value scale to use in measuring the intensity and costs of hospital services, regardless of the place of service--inpatient or outpatient. The Pittsburgh Research Institute's AMBULATORY SERVICE WEIGHTING SYSTEM (ASWS) is a service-driven relative value scale. The major components of the system are: 1) a classification of services and procedures provided in ambulatory settings; 2) a cost-based relative intensity weight for each service; and 3) a computerized system that assigns a relative weight to each ambulatory patient based on the specific services recorded on the patient bill and rendered during a particular visit or in multiple encounters. Computerized decision rules are also incorporated as edits to adjust for inconsistent revenue or procedure coding practices. The system basically standardizes the millions of outpatient claims received by third party payors so that intensity can be measured consistently across providers, and payment systems can be modified accordingly. The ASWS identifies service intensity on the same relative value scale as inpatient care, and thus, it can serve as a site-neutral classification of health care services for prospective payment and utilization management as well as a measure of resource intensity.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Arbitman DB. A primer on patient classification systems and their relevance to ambulatory care. J Ambul Care Manage. 1986 Feb;9(1):58–81. [PubMed]
  • Starfield B, Weiner J, Mumford L, Steinwachs D. Ambulatory care groups: a categorization of diagnoses for research and management. Health Serv Res. 1991 Apr;26(1):53–74. [PMC free article] [PubMed]
  • Tenan PM, Fillmore HH, Caress B, Kelly WP, Nelson H, Graziano D, Johnson SC. PACs: classifying ambulatory care patients and services for clinical and financial management. J Ambul Care Manage. 1988 Aug;11(3):36–53. [PubMed]
  • Young WW, Joyce DZ, Bivens GD, Lander SA, Macioce DP. Incorporating the cost of ambulatory care into case mix-based hospital reimbursement. J Ambul Care Manage. 1988 Aug;11(3):54–67. [PubMed]

Articles from Proceedings of the Annual Symposium on Computer Application in Medical Care are provided here courtesy of American Medical Informatics Association