Study objective: To evaluate if direct substitution of
arm span for height during interpretation of spirometry data leads to
any significant statistical or clinical differences in Indian adults,
and to compare this method with the use of height estimated indirectly
from arm span.
Setting: Respiratory laboratory of a tertiary referral
hospital in North India.
Participants: Two hundred
twenty-eight subjects referred for spirometry.
and results: Standing height and arm span were measured for all
subjects. Spirometry measurements included FVC, FEV1,
FEV1/FVC, peak expiratory flow, and maximal midexpiratory
flow. Predicted values for each parameter were calculated separately
for height, arm span, and height estimated from fixed height:arm span
ratio. Results were classified into normal, obstructive, and
restrictive defects for each height, arm span, and estimated height
measurement, and any abnormality was categorized as mild, moderate, or
severe. Arm span exceeded height in 182 (79.82%) subjects.
Thirty-seven (16.2%) and 32 (14.0%) results were classified or
categorized incorrectly when arm span and estimated height were
substituted respectively, for actual height, with a kappa estimate of
agreement 0.779 and 0.808, respectively; 17.4% and 11.0% normal
results were classified, respectively, as restrictive defects using arm
span and estimated height. Limits of agreement, which were almost
equally wide for both sets of data, were more than the permissible
intraindividual variability for FVC and FEV1.
Conclusions: The substitution of arm span for height
introduces statistically significant changes in spirometry results. Use
of height estimated from arm span using fixed ratio also leads to
misclassification of data, though less than that caused by use of arm
span alone. Height estimated from arm span can be substituted for
actual height in patients in whom height cannot be measured reliably.
Where racial/ethnic norms for height and arm span correlation are not
available, arm span is a reasonable surrogate for standing
Abbreviations: FEF25–75% = maximal
midexpiratory flow; PEF = peak expiratory flow