Experience of coding ambulatory visits to outpatient clinics.

Clinical data for all current outpatients at a large tertiary hospital has been collected for analysis. Patient diagnoses for selected "key" clinics have been coded to ICD-9-CM standards. Methods to reduce the volume of coding required for such data collection are discussed, and include short-lists of codes, default assignment of diagnoses codes according to the nature of visit, and producing a "discharge" summary for outpatients, similar to that routinely produced for inpatients.