Table 3 Differentiating abilities of relevant items and overall model performance.

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

  

Scenario 1

Scenario 2

Scenario 3

Subsection

 

Asthma

COPD

pm

Asthma

COPD

pm

Asthma

COPD

pm

Medical history questions

Age

0.97

(0.94, 1.01)

1.03

(1.00, 1.06)

0.096

0.96

(0.92, 0.99)

1.05

(1.01, 1.09)

0.014

0.93

(0.88, 0.97)

1.08

(1.03. 1.13)

0.003

Gender (female)

xl

x

x

Packyearsa

0.97

(0.95, 0.99)

1.03

(1.01, 1.06)

0.015

0.98

(0.96, 1.00)

1.02

(1.00, 1.05)

0.10

x

Wheezeb

2.76

(1.33, 5.57)

0.36

(0.17, 0.75)

0.007

3.62

(1.52, 8.59)

0.28

(0.12, 0.66)

0.004

2.79

(1.15, 6.75)

0.36

(0.15, 0.87)

0.023

Phlegmc

0.33

(0.12, 0.90)

2.99

(1.11, 8.08)

0.030

x

x

Breathlessnessd

x

2.60

(1.05, 6.40)

0.39

(0.16, 0.95)

0.038

2.55

(1.01, 6.46)

0.39

(0.15, 0.99)

0.049

Ever respiratory allergye

6.97

(3.38, 14.35)

0.14

(0.07, 0.30)

<0.001

4.37

(2.01, 9.50)

0.23

(0.11, 0.50)

<0.001

5.47

(2.49, 11.99)

0.18

(0.08, 0.40)

<0.001

Respiratory problemsf

x

x

x

Lung function tests available to primary care

FEV1 % predicted ECCSg

   

1.07

(1.03, 1.10)

0.94

(0.91, 0.97)

<0.001

1.08

(1.04, 1.11)

0.93

(0.90, 0.96)

<0.001

FEV1/FVCh < 0.70

   

0.14

(0.04, 0.52)

7.25

(1.92, 27.45)

0.004

0.11

(0.03, 0.44)

8.81

(2.27, 34.18)

0.002

Lung function tests available to secondary care

RV/TLCa

      

1.06

(0.99, 1.14)

0.94

(0.88, 1.01)

0.096

Diffusion capacityi

      

x

Model performance

Explained variancej

0.41

0.54

0.56

 

AUCk (95%CI)

p-value for difference between AUCs

0.84

(0.78–0.89)

–

0.89

(0.84–0.93)

0.020n

0.89

(0.85–0.94)

0.967o

  1. Odds ratios (95% confidence intervals) for diagnosing asthma or COPD together with corresponding p-values are calculated for the three different scenarios based on the items available.
  2. AUC area under the curve, ECCS European community of coal and steel, FEV1 forced expiratory volume in 1 s, FVC forced vital capacity, ROC receiver operator characteristics, RV residual volume, TLC total lung capacity.
  3. aPackyears were missing in 2 subjects, RV/TLC in 3 subjects; there were no further missings.
  4. bWheeze with or without breathlessness (in previous 12 months).
  5. cPhlegm after getting out of bed (in previous 12 months).
  6. dBreathlessness on exertion (in previous 12 months).
  7. eAllergic to pollen, animals, dust mites or seasonal symptoms.
  8. fRespiratory symptoms triggered by cold air, smoke or (exhaust)fumes.
  9. gPostbronchodilator FEV1 as % of predicted value.
  10. hPostbronchodilator FEV1/FVC.
  11. iDiffusion capacity in mmol/kPa/min.
  12. jNagelkerke R square.
  13. kAUC of ROC curve with COPD as reference group.
  14. l‘x’ refers to variables manually removed from the model as p-values were >0.10.
  15. mFor the difference between asthma and COPD diagnoses within each scenario separately.
  16. nFor the difference between Scenarios 2 and 1.
  17. oFor the difference between Scenarios 3 and 2.
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