ABSTRACT
The normal spirometric reference values for Thai people are still not yet available. The aim of this study was to establish standard spirometric equations for Thai people. Subjects 10 years of age and over were selected and their demographic distributions represented that of the population of the whole country. Inclusion criteria were strictly lifetime nonsmokers, no history of chronic cardiopulmonary disease (using a modified ATS--DLD 78 respiratory adult questionnaire), normal standard chest radiograph and unremarkable physical examination. They had to be without respiratory symptoms at the time of the study. Spirometric values were obtained by 5 turbine system 'Pony graphic' (Cosmed, Italy) spirometers which met ATS recommendations. A normal group of 2299 women and 1655 men were selected. Regression analyses using sex, height and age as independent variables were used to provide equations for predicted values. The results were: [table: see text] FVC and FEV1 from this study are close to the Chinese but are 8-20 per cent lower than the Caucasians. These predicted equations are recommended to be used for future reference values in the Thai population.