The CR Alpha Diagnostic Coding System for ambulatory care.

A three-digit code system for patient encounters in ambulatory care was constructed to meet the criteria of integrity, retrievability, flexibility, and acceptability. The system is distinguished from other comparable codes by the use of an alphabetical letter as a category designator, the provision of "open" areas within each category for the addition of new rubrics in appropriate sequence, and the availability of "open" categories for use in research or expansion. The system has the capacity to expand from 22 primary categories to 97 subheadings and to a maximum of 3,200 rubrics. The system uses both diagnostic and symptom-oriented rubrics. The diagnostic terms are adopted from the International Classification of Diseases, Adapted, Eighth Revision (ICDA-8) and the symptoms from the National Ambulatory Medical Care Survey Symptom Classification.