Characteristics of the 2,026 adults who participated in both examinations and had a valid spirometry test.

BMI = weight/ height2; COV = Coefficient of variability, expressed as medians, 25th and 75th percentiles. SD = Standard deviation; FET = forced expiratory time; pre-BD = before bronchodilator; post-BD = after Bronchodilator. Good quality = three acceptable tests with two best FEV1 and FVC within <150mL. LLN = lower limit of normal; 95%CI = 95% confidence interval. Characteristics of the 2,026 adults who participated in both examinations and had a valid spirometry test.