Using insurance claims to measure health status: the Illness Scale.

Health insurance systems are generating large numbers of claims filed by physicians and hospitals for reimbursement and accounting purposes. This paper describes and evaluates a measure of health status derived from physician and hospital claims filed for a sample of older Canadians during 1970-1977. Information on the number, type, and seriousness of reported diagnoses and the number and duration of hospitalizations and surgeries during each year were combined to generate annual Illness Scales ranging from 0 to 24. Alpha coefficients, measures of internal consistency, were between 0.82 and 0.84. Consistent with high validity, Illness Scale scores increased with age, were significantly associated with other health measures, and were strongly predictive of death and hospitalization in the following year. The ability to develop valid and reliable health status measures from insurance claims substantially expands the potential use of these data for research and evaluation.