Table 2.

Independent diagnostic items combined for COPD defined by panel (a), FEV1/FVC <0.7 (b), and FEV1/FVC < lower limit of normal (c) in 400 patients presenting with persistent cough

Diagnostic item	ORa (95% CI)	P-value	beta
(a) COPD panel diagnosis
Age (per 5 years)	1.3 (1.2 to 1.4)	<0.001	0.2
Male sex	1.9 (1.1 to 3.1)	0.005	0.6
Current smoking	2.7 (1.5 to 4.8)	<0.001	1.0
>20 pack-years smoking	2.1 (1.2 to 3.6)	0.003	0.7
Cardiovascular disease	1.7 (0.9 to 3.2)	0.04	0.6
Wheezing (symptom)	1.9 (1.1 to 3.2)	0.004	0.6
Wheezing on auscultation	2.0 (1.0 to 4.0)	0.02	0.7
Diminished breath sounds	2.0 (1.0 to 4.1)	0.02	0.7
Constant			–5.6
ROC areaa (95% CI)	0.79 (0.74 to 0.83)
(b) COPD FEV1/FVC < 0.7
Age (per 5 years)	1.3 (1.2 to 1.4)	<0.001	0.3
Phlegm	1.7 (1.0 to 2.3)	0.07	0.5
Current smoking	1.7 (1.0 to 2.9)	0.05	0.5
>20 pack-years smoking	2.2 (1.3 to 3.8)	0.003	0.8
Cardiovascular disease	2.0 (1.1 to 3.6)	0.02	0.7
Wheezing (symptom)	1.9 (1.2 to 3.1)	0.004	0.6
Constant			–6.0
ROC areaa (95% CI)	0.71 (0.66 to 0.76)
(c) COPD FEV1/FVC < LLN
Phlegm	2.1 (1.0 to 4.2)	0.03	0.7
Current smoking	1.7 (0.9 to 3.0)	0.08	0.5
>20 pack-years smoking	1.6 (0.9 to 2.8)	0.10	0.5
Cardiovascular disease	2.0 (1.1 to 3.6)	0.02	0.7
Wheezing (symptom)	1.9 (1.1 to 3.2)	0.01	0.7
Constant			–2.7
ROC areaa (95% CI)	0.67 (0.61 to 0.73)

COPD = chronic obstructive pulmonary disease. FEV1 = forced expiratory volume in 1 s. FVC = forced vital capacity. LLN = lower limit of normal. OR = multivariable odds ratio.

^aORs and ROC areas adjusted for over-optimism. Example linear predictor from (a): estimated risk of COPD as panel diagnosis = 1/(1 + exp –(–5.6 + 0.2*every 5 years above 50 + 0.6*male sex + 1.0*current smoking + 0.7*>20 pack-years + 0.6*cardiovascular disease + 0.6*wheezing symptom + 0.7*wheezing on auscultation + 0.7*diminished breath sounds)).