Table 1 Clinical features and lung function values of patients diagnosed with asthma and patients diagnosed with COPD.

From: Diagnostic differentiation between asthma and COPD in primary care using lung function testing

 

Chronic airways disease

No chronic airways disease

 

Asthma

COPD

p-value

 

n (% of total)

84 (16)

138 (26)

 

310 (58)

Demographic characteristics

 Age

  Mean (SD)

52.0 (11.4)

57.8 (10.0)

<0.001

54.4 (10.5)

  Median (IQR)

49.8 (14.6)

57.0 (15.2)

<0.001

53.5 (14.2)

  Range (youngest, oldest)

36.6 78.9

36.9 80.5

 

36.2, 80.7

 Gender (% female, n)

59.5 (50)

44.2 (61)

0.027

56.1 (174)

 BMI (mean, SD)

27.4 (4.3)

26.7 (4.0)

0.22

26.8 (4.0)

Smoking behaviour

 Ever smoking (%, n)

56.0 (47)

81.0 (111)

<0.001

65.5 (203)

 Current smoking (%, n)

17.9 (15)

39.1 (54)

0.001

18.1 (56)

 Packyear (mean, SD)

8.9 (14.4)

21.3 (19.5)

<0.001

10.8 (14.2)

Atopy (%, n)

 Ever allergya

70.2 (59)

19.6 (27)

<0.001

7.7 (24)

 Ever eczema

26.2 (22)

26.1 (36)

0.99

16.1 (50)

 Hyperresponsiveness (%, n)

Respiratory symptoms triggered by cold air smoke or (exhaust)fumes

71.4 (60)

59.4 (82)

0.071

22.6 (70)

Family historyb (%, n)

 Asthma

19.0 (16)

15.9 (22)

0.32

11.9 (37)

 COPD

29.8 (25)

36.2 (50)

0.65

17.1 (53)

Current respiratory medicationc (%, n)

 Bronchodilator(s)

20.2 (17)

16.7 (23)

0.502

2 (0.6)

 Inhaled corticosteroid

13.1 (11)

9.4 (13)

0.392

0

Respiratory symptoms (%, n)

 Coughd

20.2 (17)

26.1 (36)

0.32

4.5 (14)

 Wheezee

46.4 (39)

27.5 (39)

0.006

4.9 (17)

 Phlegmf

11.9 (10)

19.6 (27)

0.14

3.9 (12)

 Breathlessnessg

40.5 (34)

30.4 (42)

0.13

4.8 (15)

Spirometry:

 PostBD FEV1/FVC (mean, SD)

74.2 (4.9)

63.3 (6.3)

<0.001

75.1 (8.0)

 PostBD FEV1/FVC < 0.70 (%, n)

15.7 (13)

97.8 (135)

<0.001

13.6 (42)

 PostBD FEV1 % predicted ECCS (mean, SD)

98.9 (13.9)

88.2 (16.2)

<0.001

107.1 (14.0)

 PostBD FEV1 % predicted GLIh (mean, SD)

91.8 (16.2)

81.9 (18.2)

<0.001

98.8 (17.9)

Reversibility (%, n)

 ΔFEV1 > 12% and >200 ml after BD

9.5 (8)

10.9 (15)

0.75

1.0 (3)

 ΔFEV1 > 15% and >400 ml after BDi

7.2 (6)

2.9 (4)

0.18j

0 (0)

Other lung function test

 RV/TLC % (mean, SD)

32.2 (8.8)

35.4 (8.1)

0.005

31.0 (6.6)

 Bronchial hyperresponsivenessk (%, n)

45.2 (38)

42.8 (59)

0.68

5.5 (17)

 Diffusion capacityl (mean, SD)

8.5 (2.2)

7.6 (3.0)

0.016

8.6 (2.2)

  1. p-values are for the comparison between the two diagnostic subgroups. Data of patients with no chronic airways disease as presented in the table serve as a general reference, but were not part of the current analysis.
  2. ECCS European Community of Coal and Steel, GINA global initiative for asthma, GLI global lung function initiative, LLN lower limit of normal based in GLI prediction equations, RV residual volume, SD standard deviation, TLC total lung capacity.
  3. aAllergic to pollen, animals, dust mites or seasonal symptoms.
  4. bFirst degree relatives.
  5. cAs prescribed by the patient’s general practitioner and/or pulmonologist.
  6. dChronic cough in winter.
  7. eWheeze with or without breathlessness (in previous 12 months).
  8. fPhlegm after getting out of bed (in previous 12 months).
  9. gBreathlessness on exertion (in previous 12 months).
  10. hBased on GLI reference equations (http://gli-calculator.ersnet.org/index.html). The % predicted FEV1 values as considered by the two chest physicians in the study were based on the 1993 ECCS reference equations. The GLI-based % predicted FEV1 values were not used by the two chest physicians.
  11. iGINA (2021) states that confidence regarding presence of bronchodilator reversibility is greater if the increase is >15% and >400mls (1).
  12. jFisher’s exact test because one cell had an expected count <5.
  13. kDecrease in FEV1 by >20% at provocative dose histamine of ≤8 mg/ml (PC20).
  14. lDiffusion capacity in mmol/kPa/mi.
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