Precision in Diagnosing and Classifying COPD: Comparison of Historical Height with Current Height and Arm Span to Predict FEV1

Abstract

Background: Measured reductions in lung function, as a result of COPD, use a measured current value and make comparisons to a determined ‘normal’ value arrived at using a regression equation based upon a patients height. Osteoporosis is a recognised co-morbidity in patients with chronic obstructive pulmonary disease (COPD) and may cause excessive height loss resulting in the ‘normal’ values and disease progression being under-estimated.Purpose: The aim of the study was to examine the height variation in a cohort of COPD patients and controls over a 7-8 years period and evaluate its impact on estimates of lung function and hence COPD progression.Methods: In 1999-2002 we studied a cohort of primary care patients in Sunderland, UK with and without COPD and reexamined 104 (56 male) during 2007-2009. We calculated FEV1% predicted for actual and estimated height (armspan/1.03 and armspan/1.01 in males and females respectively).Results: In 1999-2002 the subjects were aged 62.6 ± 9.4 years, BMI was 26.4± 4.7 kg/m2, predicted FEV1 was 59.0 ±16.0, and mean actual height was 167.3±8.9cm. The actual height changed significantly (p<0.001) by 2cms over time in both genders. Whilst the overall classifications of the cohort did not change significantly when armspan was used to determine height and hence normal lung volume, individual cases did move to a classification of higher severity.Conclusions: The study suggests that current measured height may underestimate the degree of impairment of FEV1 and hence progression of COPD. The use of height, derived from armspan, may give a more accurate measure of ‘normal’ lung volumes and hence the degree of impairment.

Impact of direct substitution of arm span length for current standing height in elderly COPD

“… 9 , 10 A previous longitudinal study suggests that current measured height may underestimate the progression of COPD, and that the use of arm span to determine height will give a more accurate measure of COPD progression. 25 We disagree with this suggestion because arm span length significantly differed from current standing height in our study. Current standing height is one of the standard variables for pulmonary function measurement; therefore, we may not be able to reliably replace standing height with arm span.…”

Best lung function equations for the very elderly selected by survival analysis

“…We used recollected height, as slight kyphosis and stoop will affect height measurement but will not alter the lung capacity in the thorax, so height recorded at a younger age might be a better estimate for lung function. A follow-up study in COPD recently found that height estimated from arm span was a better measure for lung function prediction [29]. Future studies in the aged may need to measure arm span as a surrogate for true height to see if this better standardises FEV 1 , to improve survival prediction.…”

Causes of misdiagnosis of chronic obstructive pulmonary disease: A systematic scoping review

“…Enright (2012) [70] suggests that we should focus on improving the quality of the spirometry tests performed, which is in line with the findings of this review. Several factors may bias the results of the spirometry test, thereby potentially causing misdiagnosis [38,48,73,74,76]. Yet, again, it seems relevant to provide better support for primary care in COPD diagnosis to improve the quality of the spirometry tests and thus limit misdiagnosis (see Table 6).…”

“…Also, physiological changes may influence the spirometry test and cause misdiagnosis. The patient's lungs and height change over time, which may lead to an incorrect lung function test, potentially causing misdiagnosis [76,77].…”