bleeding" may be interpreted differently in practice by different observers. Bleeding defined in terms of volume loss or hematocrit drops is more precise. Even if definitions are unambiguous, a problem remains if they are not uniformly used. In this context, a controlled vocabulary is one specified by those responsible for an information system and one that precludes users from adding unauthorized terms.

Developing a controlled vocabulary and implementing it are long-term challenges. Several schemes have been developed to increase uniformity in the coding of patient history and physical results, medical diagnoses, or procedures. They go under a variety of abbreviations and acronyms (e.g., ICD-9-CM, CPT-4, SNOMEDIII) and are described in detail elsewhere (e.g., PPRC, 1988; IOM, 1991; AMA, 1993; CAP, 1993; Gibson and Middleton, 1994). To build on these efforts, the National Library of Medicine has developed a Uniform Medical Language System (UMLS) Metathesaurus to map terms used by such schemes.

Conclusion

This chapter has reviewed issues in measuring and evaluating critical outcomes for telemedicine and proposed general evaluation questions in four key areas: quality, access, cost, and patient and clinician perceptions and satisfaction. Depending on the application and clinical problem, the setting and patient population, the objectives of the program, and other factors, evaluations will differ in the outcomes of greatest interest and relevance. As stressed in Chapter 6, the earlier and more precisely evaluation objectives and questions are identified, the more likely it is that the program to be evaluated can be designed and implemented in ways that will help provide useful and credible answers.

Although the questions about quality, access, cost, and patient and clinician perceptions are presented sequentially above, their interrelationships also warrant attention. For example, the timeliness of care—an element of access as defined here—may have important consequences for quality through earlier detection and better management of clinical problems. Similarly, economic analyses of telemedicine do not simply examine costs but attempt to relate the costs of an application to its benefits and to suggest bases for judging whether the benefits are worth the costs in comparison to other



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