G.T.CHAI1, D.QI1, C.Y.GAN1, W.Y.LIM1, A.CHOW1, J.A.ABISHEGANADEN1, G.P.TAN1
Tan Tock Seng Hospital1
Studies of normal spirometry indices in healthy Singaporean Chinese adults were done between the 1960s to 1990s. Differences in pulmonary function in between successive birth cohorts may limit the applicability of the old reference values to the current population. We aim to investigate the differences in forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) of a contemporary cohort against existing reference values by Poh SC (1969), JL Da Costa (1971), Chia SE (1993) and the Global Lung Initiative (GLI).
This is a cross-sectional study involving healthy (never or minimal [<5 pack-year] smoker) adult volunteers from hospital staff and visitors. Detailed demographic and anthropometric data were collected. Spirometry was performed according to ATS/ERS standards on daily calibrated equipment (Vyaire Medical, USA) by trained laboratory personnel. Differences in mean FVC and FEV1 were compared using t-test.
One hundred and thirty-three Singapore residents were recruited from June 2019 to April 2021. Eighty-two (62%) subjects were female. The mean (standard deviation) age was 36(11) years and body mass index was 23.5(4.2) kg/m2. Most subjects achieved good spirometry quality (88% Grade A). The existing reference values significantly underestimated the FVC and FEV1 values in both genders with mean difference ranging from -0.16L to -0.58L (p<0.05). The difference in predicted values was less in the later reference equations compared to the earlier ones.
Existing reference values significantly underestimates forced expiratory lung volumes in Singaporean Chinese, likely due to cohort effect. This study highlights the importance of interval examination of laboratory normative data.