Controversies in spirometry
CMAJ 1997;157:367
Re: "Spirometry utilization in Ontario: practice patterns and policy implications," CMAJ 1997;156:169-76 [abstract / résumé] by Dr. B. Chan and colleagues and "Spirometric testing: How much is enough?" (CMAJ 1997;156:202-4 [abstract / résumé]) by Dr. Nicholas Anthonisen
In response to: A.J. Ham Pong; R.W.T. Haddon
We did not intend to suggest that FV loops are being used excessively in comparison with simple spirograms. FV loops provide physicians with a visual aid to diagnosis and are useful in the detection of high airway obstruction, an uncommon condition. Furthermore, the additional technician time needed to perform the full FV loop instead of a simple spirogram is small. Nonetheless, the usefulness of information from FV loops on small airways obstruction should be put into contxChange in flows at low lung volumes must be interpreted with caution because of measurement problems. Flows at low volumes can vary widely even in the same patient; they are also influenced by the absolute lung volume at which they were performed, which cannot be measured by spirometry. Interpretative uncertainties also exist. First, isolated reduction in flows at low lung volumes are not synonymous with but suggestive of disease in the small airways. Second, the clinical significance of an isolated reduction in an individual is unknown.
The key issue is that, although FV loops have modest benefits over simple spirograms, there is a large difference in the fees paid for them; this difference is out of proportion to the marginal benefits and cost to the provider. The fee difference, combined with the shift from spirograms to FV loops, was a key factor driving expenditure growth. If the health care system were truly interested in remunerating tests in keeping with the quality of the information they provided, we would suggest that a premium be paid for a FV test performed in a regulated facility with calibrated closed-circuit dry spirometers but not for a spirometry test performed with a hand-held model in an unregulated setting in which there is no information about the training of technical staff, no assurance of quality control and no assurance that the test will be correctly interpreted.
Clinical practice parameters for FV loop studies, such as Dr. Haddon describes, would indeed be welcome. Issues include the indications for peak expiratory flow tests, the appropriate frequency of follow-up spirometry and the use of spirometry during routine physical examinations and acute respiratory illnesses. Until these issues are clarified, we can expect the same pattern of wide variations in spirometry use to continue.
Benjamin Chan, MD, MPH, MPA
Geoffrey Anderson, MD, PhD
Institute for Clinical Evaluative Sciences in Ontario
North York, Ont.
Robert E. Dales, MD, MSc
Departments of Medicine and of Epidemiology and Community Health
University of Ottawa
Ottawa, Ont.
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