Study objective: To derive spirometry normative values
from a large population of American Indian adults and compare them to
reference values for white adults.
function was assessed using spirometry in participants of the Strong
Heart Study, a multicenter, community-based, prospective study of
cardiovascular risk factors and disease in American Indians, utilizing
American Thoracic Society guidelines and a vigorous quality assurance
Setting: Central Arizona, southwestern
Oklahoma, central South Dakota, and northeastern North Dakota.
Participants: Acceptable spirometry results were obtained
from 1,619 women and 1,005 men aged 45 to 74 years.
Results: Internal reference values and normal ranges for
FEV1, FVC, and the FEV1/FVC ratio were derived
from a healthy subgroup of 253 women and 190 men, identified by
excluding participants with factors associated with a lower
FEV1. Ten percent of the entire cohort (269 of 2,624
subjects) had airways obstruction, as defined by an
FEV1/FVC below the lower limit of the normal (LLN) using
the internal reference equations. After allowing for measurement“
noise,” 31 participants were below the LLN using reference
equations for white adults from the large National Health and Nutrition
Examination Study (NHANES) III study but were normal using the internal
reference equations (1.3% false-positive), while 27 participants were
classified as normal using NHANES III equations but had airways
obstruction using the internal reference equations (1.2%
false-negative). Similarly low misclassification rates were seen for a
low FVC (prevalence, 17.6%).
Conclusion: For clinical
purposes, NHANES III spirometry reference equations for white adults
may be used when testing American Indian women and men aged 45 to 74