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”2and 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
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/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
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