Background:
There is little data to accurate interpretation of spirometry data in South
Asia, a major global region with high reported burden for chronic
respiratory disease.
Method:
We measured lung function in 7,453 healthy men and women aged over
18 years, from Bangladesh, North India, South India, Pakistan and Sri
Lanka, as part of the South Asia Biobank study. We first assessed the
accuracy of existing equations for predicting normal forced vital capacity
(FVC), forced expiratory volume in 1s (FEV1), and FEV1/FVC ratio. We
then used our data to derive (N=5,589) and internally validate
(N=1,864) new prediction equations amongst South Asians, with further
external validation amongst 339 healthy South Asians living in
Singapore.
Results:
GLI2012 and NHANESIII consistently overestimated expiratory volumes
(best fit GLI-SEA, mean [sd] z-score: FEV1 -1.29 [1.04]; FVC -1.12
[1.12]). Age, height and weight were strong predictors of lung function
in our participants (P<0.001), and sex specific reference equations using
these three variables were highly accurate in both internal validation (z-
scores: FEV1 0.03 [0.99]; FVC 0.04 [0.97]; FEV1/FVC -0.03 [0.99]) and
external validation (z-scores: FEV1 0.31 [0.99]; FVC 0.24 [0.97];
FEV1/FVC 0.16 [0.91]). Further adjustment for study regions improves
the model fit, with highest accuracy for estimation of region specific lung
function in South Asia.
Conclusion:
We present improved equations for predicting lung function in South
Asians. These offer the opportunity to enhance diagnosis and
management of acute and chronic lung diseases in this major global
population.