Objective: To describe growth and regional variation in the use of spirometry (flow studies) in Ontario.
Design: Retrospective analysis of Ontario Health Insurance Plan (OHIP) fee-for-service billing data for spirometry from the 1989-90 to 1994-95 fiscal years.
Setting: Physicians' office practices in Ontario.
Outcome measures: Number of flow studies and associated expenditures, number and specialty of physicians performing flow studies and the distribution of their billings, number of studies per capita by age group of patients, expenditures by region and measures of variation among regions.
Results: In 1994-95, $14.13 million was spent on flow studies in Ontario. This expenditure increased by 36.9% from 1989-90 to 1994-95, exceeding the overall growth rate of 20.8% for all expenditures under OHIP. Expenditure growth was driven by an increase in the number of physicians performing spirometry rather than a higher volume of services performed per physician. The substitution of flow-volume loops, for which the fee is higher, for simple spirograms also contributed to expenditure growth. There were wide regional variations in spirometry utilization. A small number of general practitioners and family physicians accounted for much of the regional variation.
Conclusions: The rapid growth in spirometry utilization may stem from the diffusion of inexpensive spirometers in physicians' offices and from increased awareness of guidelines promoting the use of flow measurements. However, the wide regional variation in utilization may indicate either incomplete implementation of spirometry guidelines or lack of direction on the appropriate frequency of spirometry use. Clearer, evidence-based guidelines and an implementation strategy are needed. Also required is further study of possible inadequate access to spirometry in low-use regions and inappropriate use in high-use regions, where spirometry use is concentrated among a small number of physicians.