The degree of similarity between diagnostic information furnished with claims and that simultaneously entered into the medical record was estimated for 1,215 private office visits in British Columbia, Canada. For each visit, claim card and chart diagnoses were compared by having three independent internists (blinded to source and type of the data) make judgments about each diagnostic pair. The judges were highly consistent internally and their judgments were stable over time. In 40 per cent of cases chart andBecause the largest volume of ambulatory medical care is provided in physicians' offices,1 more information and understanding of these patient contacts is needed. In the medical office visit, an often-complex diagnostic and therapeutic process is generally reduced to a few terse lines of text on the patient's chart and, in many cases, to a "reason for visit" or "diagnosis" on a third party payment claim form. The investigator in ambulatory care usually has little choice but to accept these data as representing ambulatory care problems or diagnoses. Similar limitations occur in the study of hospital care or in the derivation of vital statistics where the use of summary sheets or death certificates, while of limited validity,2 3 is nonetheless useful. In some studies, however,4-6 it has been possible to have well-trained, often medically-qualified observers observe a physician-patient visit and record or infer the data being sought. Unfortunately, the expense, unacceptability to patients and doctors, perturbation, and observer variability associated with this procedure have limited the number of these studies to small populations and often to highly specialized circumstances.The widespread introduction of health insurance plans, with associated claims systems, has in recent years provided investigators with a new source of medical-visit data, often in coded computer-compatible form. In spite of inevitable limitations of these data,7 some studies have been published8-12 in which it was assumed that the claims-associated diagnostic data were acceptable representations of the actual visit content. claims data were judged dissimilar, and in 38 per cent of cases claims data were judged more valuable as a reflection of the primary problem treated. The degree ofjudged similarity of chart and claims data correlated significantly and negatively with physician workload, income, and judges' preference for the billing card diagnosis. We conclude that in using claims data to determine the content of ambulatory visits, independent validation of such data may be important. (Am J Public Health 1981; 71:145-149.) To shed further light on the validity of claims data, we studied 1,215 office visits, and compared the chart information with that submitted to a third party payor.
MethodsThe clinic studied was located in a British Columbia community of 65,000 and was comprised of 12 primary-care and five specialist physicians whose practice experience ranged from one to 35 years. Ninety-three per cent of visits were bi...
