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Table 2 Comparison of physiologic and clinical variables between ever-smokers with normal FEV1 and FEV1/FVC > LLN but < 0.70 (“discordant” group), ever-smokers with normal FEV1 and FEV1/FVC > 0.70, and never-smokers with normal FEV1 and FEV1/FVC > 0.70

From: Heterogeneous burden of lung disease in smokers with borderline airflow obstruction

Clinical Outcome

Group 1

Ever-smokers, Normal FEV1,\( \frac{\mathrm{FEV}1}{\mathrm{FVC}} \) < 0.7 and > LLN

(Discordant Group)

(n = 161)

Group 2

Ever-smokers, Normal FEV1,

\( \frac{\mathrm{FEV}1}{\mathrm{FVC}} \)>  0.7 (n = 940)

Group 3

Never-smokers, Normal FEV1,

\( \frac{\mathrm{FEV}1}{\mathrm{FVC}} \)>  0.7 (n = 190)

Overall p-value* Unadjusted (Adjusted)

P-values for pairwise comparisons (Unadjusted)

Group 1 vs. 2

Group 1 vs. 3

Group 2 vs. 3

FEV1% predicted

92.1 ± 12.0

97.5 ± 12.8

102.0 ± 11.5

<  0.001 (<  0.001)

<  0.001

<  0.001

<  0.001**

FEF25–75% % predicted

61.2 ± 11.0

102.3 ± 33.4

121.3 ± 32.5

<  0.001 (<  0.001)

<  0.001

<  0.001

<  0.001**

6MWD (m)

437.5 ± 109.6

437.2 ± 97.7

479.3 ± 103.4

<  0.001 (0.49)

0.97

<  0.001

< 0.001**

St George’s Respiratory Questionnaire Total Score

22.5 ± 17.4

24.2 ± 19.1

8.8 ± 10.0

<  0.001 (<  0.001)

0.28

<  0.001

<  0.001**

COPD Assessment Test (CAT)

10.7 ± 7.4

11.3 ± 8.1

4.7 ± 6.0

< 0.001 (<  0.001)

0.36

< 0.001

< 0.001**

Use of either inhaled corticosteroid or bronchodilator

34.4%

25.1%

3.9%

< 0.001 (< 0.001)

0.01

< 0.001

< 0.001†

Chronic bronchitis

17.3%

17.8%

2.1%

< 0.001 (< 0.001)

0.88

< 0.001

< 0.001†

mMRC Dyspnea score ≥ 2

13.8%

13.6%

2.7%

< 0.001 (0.007)

0.95

< 0.001

< 0.001†

Change in FEV1 (ml/year)

− 60.5 ± 120.5

−55.2 ± 127.5

−41.2 ± 99.7

0.32

(0.94)

0.64

0.17

0.19**

Exacerbation (#/year)

0.1 ± 0.4

0.1 ± 0.6

0.02 ± 0.1

0.02

(0.21)

0.50

0.13

0.006**

  1. Emphysema = % of voxels with CT attenuation <− 950 Hounsfield Units (HU) on full inspiration. Functional small airways disease = % of voxels with CT attenuation > − 950 HU on the inspiratory exam and < − 856 HU on the expiratory scan, as determined via dynamic image registration (Parametric Response Mapping, PRM). Airway thickening = square root of the wall area for a standardized airway with an internal perimeter of 10 mm (Pi10)
  2. *From likelihood ratio test comparing means of 3 groups from multivariable model with outcomes (rows) and group status as predictors adjusted for age, sex, race, smoking history (pack-years) and current smoking
  3. **p-values from 2 sample t-test
  4. Pairwise p-value form Wald test comparing means of 2 groups