Could symptoms and risk factors diagnose COPD? Development of a Diagnosis Score for COPD

Figures & data

Table 1 Reported chronic symptoms, spirometry, and COPD

Symptoms	Number (total)	Normal spirometry	P value	COPD (%)	Kappa; P value
Chronic cough			<0.001		0.252;
No	1690	77.7%		7.9%	<0.001
Yes	511	45.4%		29.2%
Morning cough			<0.001		0.117;
No	1973	71.9%		11.6%	<0.001
Yes	228	55.1%		24.6%
Evening cough			0.009		0.037;
No	2161	70.5%		12.6%	0.005
Yes	40	51.3%		27.5%
Night cough			<0.001		0.051;
No	2100	71.3%		12.4%	0.005
Yes	100	47.0%		22.0%
Cough all day			<0.001		0.301;
No	2005	74.5%		9.7%	<0.001
Yes	196	26.0%		45.9%
Chronic sputum			<0.001		0.271;
No	1632	77.8%		7.0%	<0.001
Yes	569	48.3%		29.7%
Morning sputum			<0.001		0.146;
No	1905	72.8%		11.0%	<0.001
Yes	296	53.7%		25.3%
Evening sputum			0.043		0.033;
No	2163	70.4%		12.7%	0.024
Yes	38	55.3%		26.3%
Night sputum			<0.001		0.043;
No	2132	71.1%		12.5%	0.008
Yes	68	42.6%		23.5%
Sputum all day			<0.001		0.273;
No	2012	73.6%		10.0%	<0.001
Yes	188	34.0%		43.6%
Any wheezing			<0.001		0.241;
No	1575	78.3%		7.2%	<0.001
Yes	626	49.8%		27.3%
Morning wheezing			<0.001		0.039;
No	2085	71.2%		12.6%	0.041
Yes	115	51.7%		19.1%
Evening wheezing			<0.001		0.059;
No	2131	70.5%		12.4%	<0.001
Yes	70	58.6%		27.1%
Night wheezing			0.031		0.074;
No	2000	71.9%		12.1%	<0.001
Yes	201	52.7%		20.9%
Wheezing all day			<0.001		0.213;
No	2048	72.9%		10.8%	<0.001
Yes	153	33.3%		40.5%
Cold becomes a lung problem			<0.001		0.211;
No	1712	76.3%		8.9%	<0.001
Yes	488	48.6%		26.8%
Any chronic allergy			0.339		0.017;
No	1722	70.7%		12.5%	0.395
Yes	478	68.4%		14.0%
Allergic rhinitis			0.885		0.004;
No	1906	70.1%		12.9%	0.861
Yes	295	70.5%		13.2%
Lung allergy			<0.001		0.068;
No	2094	71.2%		12.3%	<0.001
Yes	106	50.5%		24.5%
At least one symptom			<0.001		0.200;
Yes	1112	54.1%		22.7%	<0.001
No	1088	86.5%		2.8%
MRC dyspnea scale	Number (total)	Normal spirometry	P value	COPD*	OR/kappa
0	1267	80.2%	Reference	7.1%	1.00
1	325	64.6%	<0.001	12.0%	1.78
2	144	66.7%	<0.001	17.2%	2.72
3	149	58.4%	<0.001	10.8%	1.58
4	146	50.7%	<0.001	26.0%	4.60
5	170	35.7%	<0.001	44.7%	10.56
MRC score > 0			<0.001
No	1267	80.2%		7.1%	0.150
Yes	934	56.5%		20.8%

Abbreviations: COPD, chronic obstructive pulmonary disease; MRC, Medical Research Council; OR, odds ratio.

Table 2 Construct validity and reliability of COPD Symptoms Index (scale*)

Scale items	Loading on factor 1	Loading on factor 2	Loading on factor 3
Cough all day	0.909
Sputum production all day	0.898
MRC score	0.420
Morning sputum production		0.888
Morning cough		0.864
Wheezing all day			1.006

Note:

* Reliability Cronbach’s alpha = 0.692.

Abbreviations: COPD, chronic obstructive pulmonary disease; MRC, Medical Research Council.

Table 3 Logistic regression^* for COPD correlates

Factor	aOR	95% CI	P value
Age class	1.49	1.31–1.70	<0.001
Female gender	0.55	0.38–0.80	0.002
Low birth weight	1.27	1.00–1.61	0.053
Heating home by diesel	1.49	1.01–2.20	0.046
Cooking on wood	2.75	1.39–5.46	0.004
Actual cigarette smoking	3.33	2.02–5.49	<0.001
Previous cigarette smoking	2.87	1.75–4.72	<0.001
Previous waterpipe smoking	2.60	1.32–5.13	0.006
MRC score	1.24	1.12–1.38	<0.001
Coughing all day	2.18	1.34–3.56	0.002
Chronic bronchitis	1.62	1.10–2.39	0.015
Wheezing all day	1.61	0.96–2.70	0.072

Notes:

* Nagelkerke R square = 0.339; Hosmer and Lemeshow adequacy test P = 0.406; 91.1% of individuals were correctly classified; dependent variable is COPD, while the independent variables include sociodemographic characteristics (age class, gender, and education), risk factors for COPD (previous and actual cigarette and waterpipe smoking, cooking on wood, heating on diesel, heating on gas, heating on wood, passive smoking, living close to a road with heavy traffic, occupational exposure to gases and fumes, living close to electricity generators), and symptoms (cough all day, sputum production all day, MRC dyspnea score, morning sputum production, morning cough, and wheezing all day).

Abbreviations: aOR, adjusted odds ratio; MRC, Medical Research Council; CI, confidence interval; COPD, chronic obstructive pulmonary disease.

Figure 1 Receiver-operating characteristic curve for threshold selection of Diagnosis Score for Chronic Obstructive Pulmonary Disease score.

Note: Area under the curve = 0.849 (0.826–0.873, P < 0.001).
Abbreviation: ROC, receiver-operating characteristic curve.

Table 4 Coordinates of the receiver-operating characteristics curve

COPD positive if ≥ (a)	Sensitivity	Specificity
1.0000	1.000	1.000
2.1667	1.000	0.997
2.6667	1.000	0.975
3.1667	1.000	0.970
3.6667	1.000	0.888
4.1667	1.000	0.884
4.3333	1.000	0.884
4.6667	0.997	0.828
5.1667	0.997	0.824
5.3333	0.997	0.824
5.6667	0.993	0.753
6.1667	0.993	0.746
6.3333	0.993	0.746
6.6667	0.969	0.661
7.1667	0.965	0.656
7.3333	0.965	0.656
7.6667	0.944	0.568
8.1667	0.934	0.562
8.3333	0.927	0.523
8.6667	0.920	0.473
9.1667	0.906	0.467
9.3333	0.906	0.449
9.6667	0.885	0.380
10.1667	0.882	0.376
10.3333	0.875	0.350
10.6667	0.812	0.280
11.1667	0.808	0.278
11.3333	0.780	0.238
11.6667	0.742	0.214
12.1667	0.735	0.212
12.3333	0.711	0.182
12.6667	0.690	0.164
13.1667	0.690	0.161
13.3333	0.606	0.122
13.6667	0.599	0.114
14.1667	0.596	0.112
14.3333	0.537	0.091
14.6667	0.516	0.083
15.1667	0.512	0.082
15.3333	0.446	0.058
15.6667	0.443	0.057
16.1667	0.439	0.057
16.6667	0.397	0.037
17.1667	0.397	0.036
17.8333	0.314	0.022
18.6667	0.254	0.016
19.1667	0.251	0.016
19.8333	0.195	0.012
20.8333	0.122	0.010
21.6667	0.087	0.006
22.1667	0.080	0.006
22.8333	0.049	0.003
23.8333	0.017	0.002
24.8333	0.014	0.001
25.8333	0.007	0.000
26.8333	0.003	0.000
28.3333	0.000	0.000

Figure 2 Percentages of COPD and of respiratory symptoms (not COPD) by category of Diagnosis Score for COPD in symptomatic individuals.

Abbreviation: COPD, chronic obstructive pulmonary disease.