Study objective: To derive spirometry normative values from a large populat
ion of American Indian adults and compare them to reference values for whit
e adults.
Design: Pulmonary 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 A
merican Thoracic Society guidelines and a vigorous quality assurance progra
m.
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 m
en, identified by excluding participants with factors associated with a low
er FEV, Ten percent of the entire cohort (269 of 2,624 subjects) had airway
s obstruction, as defined by an FEV1/FVC below the lower limit of the norma
l (LLN) using the internal reference equations. After allowing for measurem
ent "noise," 31 participants were below the LLN using reference equations f
or white adults from the large National Health and Nutrition Examination St
udy (NHANES) III study but were normal using the internal reference equatio
ns (1.3% false-positive), while 27 participants were classified as normal u
sing NHANES III equations but had airways obstruction using the internal re
ference equations (1.2% false-negative). Similarly low misclassification ra
tes were seen for a low FVC (prevalence, 17.6%).
Conclusion: For clinical purposes, NHANES III spirometry reference equation
s for white adults may be used when testing American Indian women and men a
ged 45 to 74 years.