The Johns Hopkins ambulatory-care coding scheme.

A classification and coding system for ambulatory-care problems has been developed at the Johns Hopkins Medical Institutions and three affiliated institutions. The provider's statement of the patient's problem, as recorded on an encounter from, is kept in a computer file. Codes from the classification scheme, based on those used in four existing schemes, are automatically assigned to diagnoses, symptoms, well-care services, and treatment procedures categorized by physiological system and subsystem. About 85 percent of recorded problems are machine-codable; the remainder are alphabetized for efficient manual coding. The coding system is integrated with an overall information system that allows linkage of coded problem data to diverse data on patient and provider characteristics. Examples are given of the uses and limitations of the linked data for care evaluation, management, and clinical research.