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Captain, United States Public Health Service, retired.
Correspondence to: John L. Hankinson, PhD, PO Box 3496, Valdosta, GA 31504-3496
In this issue of CHEST (see page 416), Eaton and colleagues report their findings on the quality of spirometry in primary care practices and the impact of spirometry workshops. In an analysis of 1,012 spirometry tests from 30 primary care practices, only 3.4% of patients in practices that received no training and only 13.5% of patients in practices that received minimal training had three acceptable maneuvers with a reproducible test. The percentages were slightly higher (12.5% and 33.1%, respectively) if the American Thoracic Society minimum requirements1 for interpreting two acceptable maneuvers were used. These findings of poor quality spirometry were observed despite the use of "built-in" spirometer quality assurance features that provide immediate feedback to the technician concerning curve acceptability and test reproducibility. In addition, the primary care physician's interpretation was judged correct for only 53% of patients.
These findings are particularly relevant to the recently published comprehensive statement, "Strategies in Preserving Lung Health and Preventing COPD and Associated Disease"2 and the continuation of this initiative with a joint American College of Chest Physicians (ACCP)/National Heart, Lung, and Blood Institute (NHLBI) consensus conference on "Office Spirometry for Lung Health Assessment in Adults."3 Both of these reports recommend the use of spirometry in primary care practice to detect COPD. The study findings suggest that poor quality spirometry may compromise the effectiveness of any screening program involving primary care practices.
Eaton and associates observed that most of the failures to obtain three
acceptable maneuvers were due to end-of-test failures: of 2,928 curves,
only 28% were 
6 s in duration. The ACCP/NHLBI consensus
report recognized the practical difficulties of obtaining a true FVC,
where long exhalations may be required, by recommending the use of the
forced expiratory volume in 6 s (FEV6) and
the FEV1/FEV6% as a
surrogate for the FVC. However, this study found that 47% of the
exhalations were < 4 s in duration and therefore the
FEV6 could not be measured. Although it is
possible that some patients (young patients in particular) may not need
6 s to reach their FVC, a visual inspection of the spirograms
showed that < 15% of the curves with end-of-test failures (no
plateau or < 6 s of exhalation) had acceptable plateaus. This
suggests that a large percentage of the test failures were indeed early
termination of effort, rather than an inappropriate application of the
end-of-test criteria.
It could be argued that regardless of the end-of-test failures and the corresponding potential errors in FVCs and FEV6s, the FEV1s may still be valid for screening purposes. This argument assumes that technicians who are unable to obtain maneuvers without end-of-test failures can successfully coach the patient to completely inhale before performing the forced exhalation. Incomplete inhalation is a common problem, and it is suspected when a test is not reproducible in the presence of strong coaching. In the absence of strong coaching, a reproducible test is less supportive of the fact that a complete inhalation was obtained. In addition, the FEV1/FVC% or FEV1/FEV6% has been shown to be relatively race independent,4 and screening for COPD without the benefits of knowing the FEV1/FVC% or FEV1/FEV6% reduces the sensitivity and specificity of the spirometry test.
Table 1 illustrates the difficulty of interpreting poor quality spirometry where the mean percent predicted FEV1 is reduced but the FEV1/FVC% is approximately 100% of predicted. Although this finding (low FEV1 without a reduction in FEV1/FVC%) may be explained by early termination, it is difficult to determine whether the sole observance of a reduced FEV1 is due to disease or to incomplete inhalation. Confirmation with good quality spirometry or measurement of lung volumes is necessary to eliminate possible false-positive test results.
In summary, this study raises serious questions about the practical usefulness of screening spirometry in a primary care practice because of the potential for large numbers of false-positive tests associated with poor quality spirometry. Training may improve the quality of spirometry results, but the minimal training provided in this study had limited impact. Similarly, the use of automated spirometer quality assessments with immediate feedback did not appear to address the end of test problems that were observed. Certainly, any abnormal test result based on a poor quality spirogram will need to be followed up with a repeat spirometry test of good quality. Because of the potential negative impact of poor quality spirometry, the practicality of a screening program in the primary care setting needs further evaluation.
References
This article has been cited by other articles:
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  M. Lusuardi, F. De Benedetto, P. Paggiaro, C. M. Sanguinetti, G. Brazzola, P. Ferri, and C. F. Donner A Randomized Controlled Trial on Office Spirometry in Asthma and COPD in Standard General Practice : Data From Spirometry in Asthma and COPD: a Comparative Evaluation Italian Study,{dagger}. Chest, April 1, 2006; 129(4): 844 - 852. [Abstract] [Full Text] [PDF]
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