© 2004 American Thoracic Society
Aging on Quality of SpirometryTo the Editor:We read with great interest the article by Enright and colleagues (1) on the reproducibility of spirometry in a wide range of an adult population. The study showed that 90% of the sample was able to provide an FEV1 reproducibility within 120 ml and an FVC reproducibility within 150 ml. In 2000, we reported the results of a quality control study on spirometry (2), focusing more on the effects of aging in health and disease. The study was performed on 638 subjects with chronic respiratory obstructive disease and 984 healthy control subjects aged 65 years and older, who participated in the SA.R.A. (i.e., Salute Respiratoria nell'Anziano ["Respiratory Health in the Elderly"]) multicenter study. The percentage of reproducibility for FEV1 was 95.8% in control subjects and 94.3% in subjects with respiratory diseases. The average difference between the largest FEV1 and the second largest FEV1 was 58 ml in the former group and 62 ml in the latter. Our findings seem to be very similar to those reported by Enright and coworkers (1), who showed an average FEV1 difference of 50 ml in the female group and 66 ml in the male group.
In our study (2), we also evaluated the importance of operators, which is underlined by Enright and colleagues (1). In fact, we demonstrated that a careful training of respiratory technicians is advocated to achieve a good quality of tests: quality of spirometry tended to increase over time (18 months, As concerns the selection of a cutoff level of FEV1 and FVC difference, Enright and colleagues (1) suggested that the American Thoracic Society (ATS) repeatability goal of 200 ml may be too lenient, because 9 of 10 patients may obtain FEV1 and FVC reproducibility within 120 to 150 ml. This conclusion may perhaps be discussed in a more aged population; actually, in our study, we observed that 94% of subjects had an FEV1 reproducibility within 150 ml. However, if we restricted the FVC reproducibility criterion to 150 ml, we would include 85% of our subjects. On this basis we believe that in an elderly population, the 200 ml criterion for reproducibility proposed by ATS could still be considered as adequate.
Università di Palermo Palermo, Italy FOOTNOTES Conflict of Interest Statement: V.B. does not have a financial relationship with a commercial entity that has an interest in the subject of this letter; F.C. does not have a financial relationship with a commercial entity that has an interest in the subject of this letter; R.P. does not have a financial relationship with a commercial entity that has an interest in the subject of this letter; R.A.I. does not have a financial relationship with a commercial entity that has an interest in the subject of this letter. REFERENCES
From the Author: Nine of every 10 people can be coached to produce good quality spirometry. I apologize to the Salute Respiratoria nell'Anziano (SARA; "Respiratory Health in the Elderly") investigators for not referencing their excellent article. Our two studies complement each other because they were performed in two different settings: a research study of a general population–based sample (1) and the pulmonary function laboratory of a large outpatient clinic (2). The American Thoracic Society and European Respiratory Society have recently produced updated and combined recommendations for pulmonary function testing that will probably recommend a spirometry repeatability goal of 150 ml for both FEV1 and FVC. I personally believe that test quality goals should be set at a level that can be reached by a skilled and experienced technologist about 90% of the time when testing a wide variety of subjects. The only disadvantage of setting the goal "too high" is that a few additional maneuvers may have to be performed with some subjects in an attempt to reach the goal. The consequence of setting the goal too low is a higher rate of misclassification of the results (both false negatives and false positives). That's bad, because physicians often rely on spirometry to confirm the diagnosis of diseases that cause airflow limitation, and then use the FEV1 to follow treatment efficacy. Several studies have shown that the most difficult spirometry quality check to meet (especially in patients with airflow limitation) is the end-of-test criterion (a flat volume–time curve during the last second or two of exhalation). Quitting too soon causes a lower FVC and a higher FEV1/FVC ratio. This problem can be solved without risking misclassification by switching to new reference equations for FEV6 and FEV1/FEV6, and then stopping all maneuvers after 6 seconds (3–5). If a valid measurement of vital capacity is needed for clinical decision-making, then the vital capacity should be measured slowly and separately from forced expiratory maneuvers. I have noticed (in more than one culture) that elderly men often do not like young women telling them what to do in a loud voice. In such cases, they may even turn down their hearing aids or practice "selective listening," which could lead the technologist to conclude that the subject was "uncooperative." When quality goals are not met after three to five maneuvers, a switch of technologist often solves the problem. We agree that independent review of the quality of spirometry tests is necessary in many settings, because the skill and experience of technologists varies widely.
University of Arizona Tucson, Arizona FOOTNOTES Conflict of Interest Statement: P.L.E. has no conflicts of interest with any lung function–testing manufacturer. REFERENCES
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2 for trend p < 0.05), and with the number of tests performed (r2 = 22%; p < 0.05). However, unlike Enright and colleagues, who do not find any effect of age on reproducibility, we demonstrated that age and male sex negatively affected the reproducibility of spirometry. In addition, we observed that age-related variables, such as cognitive and physical impairment (together with a lower educational level), are independent risk factors for a poorer acceptability. Differences in age distribution of the samples may perhaps explain the different evaluation of the relationship between age and reproducibility.