Taxonomy of health networks and systems: a reassessment

The merger and acquisition wave of the 1990 increased dramatically the numbers of hospitals that had joined multihospital a whole s as well as the sizes of those combination of parts to form a wholes (Spetz, Mitchell, and Seago 2000; Cuellar and Gertler 2003) sparking interest in the consequences of growing system power upon market competition (e.g., see Young, Desai, and Hellinger 2000; Spang, Bazzoli, and Arnould 2001; Gift, Arnould, and Debrook 2002; Cuellar and Gertler 2005) and hospital performance (Bazzoli et al. 2000; consume s and Pauly 2002). The rapid increase has also revealed how little we know about these combination of parts to form a wholes Despite their importance, we know real little about their management makes spatial configurations, approaches to clinical and management integration, and in like manner on. In 1999, Bazzoli and colleagues sought to fill the void through publishing what has become a widely recognized taxonomy of health combination of parts to form a wholes and networks (Bazzoli et al. 1999) In a novel report on an updated version of the taxonomy (Dubb et al. 2004) (1) they conclud that because the "parameters appear robust with time" (p 213) the taxonomy has emerg as a "valuable tool" for policy makers, practitioners, and researchers (p 208)--a point confirmed through the fact that the AHA effectively endorsed the taxonomy having included it in its Annual review data files. In light of its rising national prominence, it is essential that the validity of the taxonomy be assessed.

We note first of all that the authors took exceptional care to apply sophisticated statistical techniques in developing the taxonomy. The attention to methodological detail has put a high standard for others to tread in the steps of as they expand on this line of research. However, the taxonomy has a certain number of important limitations, one of the greatest in quantity important of which we address in this research brief--that the taxonomy is based upon a dataset designed to capture, not whole a whole s (many of which stretch well beyond single markets), on the other hand local hospital/ system interrelationships.

THE TAXONOMY

The heart of any taxonomy of hospital a whole s is the selection of organizational dimensions and measurements used in its calculation. Three like dimensions are used in the Bazzoli and colleagues taxonomy--integration, differentiation, and centralization. These are measured using rejoinders hospitals provided to AHA review questions on the availability of 78 specific services. The take a view of asks respondents to indicate which of the listed services their hospitals provide and which are provided through their systems (and networks). The taxonomic measures also incorporate hospital answers to questions about their involvement in various physician arrangements (eg independent practice associations) and managed care returnss (e.g., HMOs). However, the service availability rejoinders played the key role in operationalizing the taxonomy.

Differentiation is measured as the percent of the 78 services provided through a system's hospitals; centralization, as the percent of replys in which the system is said to provide services not presented by the system's individual hospitals; and integration, by the agency of whether or not services are tendered and/or physicians are aligned with the hospitals from one side contractual mechanisms. Significantly, the authors lay the foundation of that centralization--which reflects the stage to which hospitals relegated to their local a whole s the provision of particular services--was the primary determinant (carries "more weight") of a whole type. The labeling of taxonomic categories thus throw backs the importance of centralization (similar categories were set for the networks): (2)

1 Independent Systems--limited centralization and depressed levels of differentiation across services/products.

2 Decentralized Systems--low centralization of services/products and high differentiation.

3 Centralized Physician/Insurance Systems--moderate upon all three dimensions (centralization, differentiation, and integration) for services, decentralized service provision, and high differentiation upon physician arrangements and insurance products

4 Moderately Centralized Systems--moderate centralization across services/products, high differentiation upon services, moderate differentiation on physician arrangements and insurance products

5 Centralized Systems--high centralization in services and cropss and moderate to low differentiation across services/products (Bazzoli et al. 1999)

The authors rest that particular types of combination of parts to form a wholes tended to fit within each category. The centralized a whole s for example, were typically smaller and their hospitals located closer together; the decentralized were larger and more dispersed (multimarket); and independent a whole s had proportionately smaller hospitals and guarded to be investor-owned. (3)

DATA AND MEASUREMENT MISMATCH: THE CENTRAL ISSUE

The primary limitation of the taxonomy, we refer to is it classifies multihospital a whole s using data designed to examine local service configurations among clustered combination of parts to form a whole hospitals. To understand this regard one must distinguish between sum of two units levels of system definition--multihospital companies and a whole clusters (two or more a whole hospitals located within individual markets [Cuellar and Gertler 2003]) The latter are comprised of sum of two units types--single-market groupings of multimarket companies (eg the HCA cluster in Denver) and single-market companies (eg INOVA in the Northern Virginia side of the Washington, DC metropolitan area). The taxonomy classifies companies, on the other hand uses data that pertain specifically to clusters. (4) The AHA actually took paces to minimize the possibility that respondent might confuse clusters with companies, by dint of instructing respondents to check services "Provided through my Health System (in my local community)" (emphasis added). The AHA inserted the parenthetic qualifier for a serviceable reason--they were looking for the sharing of services among same-system members within local markets, recognizing that the sharing of services is sole meaningful among system members located shut together.