Which is the Best Screening Strategy for COPD among Smokers in Primary Care?

Figures & data

Table 1. Independent variables for COPD obtained in the prevalence study (n = 1738 individuals) used for developing the EGARPOC questionnaire.

COPD	OR	CI 95%	z	p (z)
Age intervals
<55 year	1
55–70 years	2.65	1.7–4.07	4.43	0.0001
> 70 years	5.94	3.7–9.55	7.35	0.0001
Sex
Women	1
Men	2.74	1.32–5.71	2.71	0.007
Body mass index (BMI)
BMI <25	1
BMI 25–30	0.63	0.42–0.93	−2.33	0.02
BMI >30	0.35	0.23–0.50	−4.99	0.0001
Pack-years
<20	1
20–40	3.11	1.89–5.1	4.48	0.0001
>40	6.19	3.84–9.98	7.48	0.0001
Profession of risk	1.91	1.4–2.59	4.1	0.0001
Do you usually expectorate?	1.61	1.18–2.2	3.01	0.003
Do you get breathless walking on flat areas?	1.72	1.26–2.35	3.42	0.001
When you have a cold, does it go to your chest?	2.25	1.64–3.09	5.03	0.0001
Have you ever needed treatment for an attack of breathlessness?	4.1	2.8–6	7.27	0.0001
Do you have cardiovascular disease?	1.72	1.23–2.4	3.2	0.001

Results of the regression analysis and the odds ratio (OR) values.

OR: odds ratio for presenting COPD. Pseudo R2 = 0.3289. CI 95%: confidence interval of 95%.

Figure 1. Area under the ROC curve for the EGARPOC questionnaire. Footnote: AUC ROC: 0.841 (0.820–0.863).

Table 2. Characteristics of the individuals included in the validation study of the questionnaires and COPD-6.

	Total	Men	Women	p
No patients (%)	407 (100%)	265 (65.2%)	142 (34.8%)
Mean age: years, mean (SD)	57.4 (8.9)	58.8 (9.4)	54.9 (7.5)	<0.0001
BMI, mean (SD)	28.5 (5.1)	29.2 (4.7)	27.1 (5.6)	<0.0001
Level of education				0.003
Low	80 (19.7%)	59 (22.3%)	21 (14.8%)
Medium	216 (53.1%)	148 (55.8%)	68 (47.9%)
High	111 (23.7%)	58 (21.9%)	53 (37.3%)
Smoking				0.104
Smoker	230 (56.5%)	142 (53.6%)	88 (62%)
Ex-smoker	177 (43.5%)	123 (46.4%)	54 (38%)
Pack-years, mean (SD)	31.6 (20.1)	34.7 (20.3)	25.9 (18.2)	<0.0001
Profession with respiratory risk				<0.0001
Yes	289 (71%)	212 (80%)	77 (54.2%)
No	118 (29%)	53 (20%)	65 (45.8%)
Cardiovascular disease				0.053
Yes	35 (8.6%)	28 (10.6%)	7 (4.9%)
No	372 (91.4%)	237 (89.4%)	135 (95.1%)
COPD (fixed ratio)				0.0001
Yes	107 (26.3%)	86 (32.5%)	21 (14.8%)
No	300 (73.7%)	179 (67.5%)	121 (85.2%)
COPD (LLN)
Yes	86 (20.6%)	66 (24.9%)	20 (14.1%)	0.011
No	321 (78.9%)	199 (75.1%)	122 (85.9%)
Degree of COPD severity (fixed ratio)				0.625
I—mild	45 (42.1%)	35 (40.7%)	10 (47.6%)
II—moderate	53 (49.1%)	43 (50%)	10 (47.6%)
III—severe	9 (8.4%)	8 (9.3%)	1 (4.8%)
IV—very severe	0	0	0
Degree of COPD severity (LLN)				0.550
I—mild	36 (41.9%)	26 (39.4%)	10 (50%)
II—moderate	41 (47.7%)	32 (48.5%)	9 (45%)
III—severe	9 (10.5%)	8 (12.1%)	1 (5%)
IV—very severe	0	0	0

BMI, body mass index; COPD, chronic obstructive pulmonary disease; LLN, lower limit of normal; SD, standard deviation.

Table 3. Results of the comparison between individuals with and without COPD in the validation study population.

	COPD (fixed ratio)	NO COPD	p	COPD (LLN)	NO COPD	p
	(n = 107)	(n = 300)		(n = 86)	(n = 321)
Sex n (%)
Men	86 (32.5%)	179 (67.5%)	<0.0001	66 (24.9%)	199 (75.1%)	0.011
Women	21 (14.8%)	121 (85.2%)		20 (14.1%)	122 (85.9%)
Mean age, years, mean (SD)	61.7 (9.1)	55.9 (8.4)	<0.0001	60. 6(9.6)	56.6 (8.6)	<0.0001
BMI, Kg/m2	28.3 (5.4)	28.5 (5)	0.676	27.2 (5)	28.8 (5)	0.011
Level of education n (%)			0.003			0.474
Low	24 (22.4%)	56 (18.7%)		20 (23.3%)	60 (18.7%)
Medium	60 (56.1%)	156 (52%)		47 (54.7%)	169 (52.6%)
High	23 (20.7%)	88 (29.3%)		19 (22.1%)	92 (28.7%)
Smoking			0.303			0.186
Smoker	65 (60.7%)	165 (55%)		54 (62.8%)	176 (54.8%)
Ex-smoker	42 (39.3%)	135 (45%)		32 (37.2%)	145 (45.2%)
Pack-years	40.5 (20.5)	28.4 (18.9)	<0.0001	38.9 (20.5)	29.6 (19.5)	<0.0001
Profession with respiratory risk	80 (74.8%)	209 (69.7%)	0.318	69 (80.2%)	220 (68.5%)	0.034
Cardiovascular disease	14 (13.1%)	21 (7%)	0.054	9 (10.5%)	26 (8.1%)	0.487
Spirometry values, mean (SD)
Pre-bronchodilator spirometry (n = 407)	107	300		86	321
FVC, L	3.69 (1)	3.82 (0.9)	0.195	3.73 (1.04)	3.80 (0.89)	0.567
FVC, %	88.6 (20.3)	95.4 (16.6)	0.002	90.7 (21.7)	94.4 (16.7)	0.094
FEV1, L	2.26 (0.7)	2.97 (1.2)	<0.0001	2.24 (0.8)	2.93 (1.2)	<0.0001
FEV1, %	72.7 (19.4)	95.6 (17.2)	<0.0001	72.6 (21.1)	94.2 (17.7)	<0.0001
FEV1/FVC, %	60.4 (8.2)	77.2 (7)	<0.0001	58.9 (8.7)	76.5 (7.3)	<0.0001
Post-brochodilator spirometry (n = 135)	107	28		86	52
FVC, L	3.83 (0.97)	4.16 (0.92)	0.102	3.88 (1)	3.91 (0.86)	0.567
FVC, %	91.8 (19.7)	103 (15.1)	0.006	94.1 (20.9)	94.3 (16)	0.094
FEV1, L	2.37 (0.7)	3.04 (0.7)	<0.0001	2.35 (0.8)	2.78 (0.7)	<0.0001
FEV1, %	76 (18.4)	97.8 (15.6)	<0.0001	75.5 (19.9)	88.83 (16.6)	<0.0001
FEV1/FVC, %	61.5 (8.1)	71.8 (4.1)	<0.0001	59.9 (8.4)	70.17 (3,03)	<0.0001

BMI, body mass index; COPD, chronic obstructive pulmonary disease; LLN, lower limit of normal; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; SD, standard deviation.

Table 4. Results of the comparison of portable spirometry values and those of the questionnaires in individuals with and without COPD by fixed ratio and LLN.

	COPD (fixed ratio)	NO COPD		COPD (LLI)	NO COPD
	(n = 107)	(n = 300)	p	(n = 86)	(n = 321)	p
Portable spirometry, mean (SD)
FEV6, L	3.09 (0.9)	3.44 (0.8)	<0.0001	3.11 (0.9)	3.42 (0.8)	<0.003
FEV6, %	87.9 (21.3)	101.2 (17.6)	<0.0001	89.3 (22.5)	100 (18.1)	<0.0001
FEV1, L	2.2 (0.7)	2.79 (0.69)	<0.0001	2.19 (0.8)	2.76 (0.67)	<0.0001
FEV1, %	78.8 (20.3)	99.9 (17.3)	<0.0001	78.7 (21.7)	98.6 (17.8)	<0.0001
FEV1/FEV6, %	71 (7.3)	81.2 (6.6)	<0.0001	70.1 (7.8)	80.5 (6.6)	<0.0001
Yellow or red color [n (%)]	46 (43)	24 (7.7)	<0.0001	37 (43)	30 (9.3)	<0.0001
Lung age	76.2 (20.1)	54.9 (16.6)	<0.0001	75.6 (21.9)	56.5 (17.3)	<0.0001
Questionnaires
RHSQ	21.06 (6.4)	15.84 (5.9)	<0.0001	20.76 (6.5)	16.26 (6.08)	<0.0001
COPD-PS	4.8 (1.2)	3.67 (1.2)	<0.0001	4.26 (1.26)	3.72 (1.18)	<0.0001
EGARPOC	13.86 (4.7)	11.1 (3.9)	<0.0001	13.9 (4.5)	11.1 (3.9)	<0.0001
Two questions	0.6 (0.5)	0.48 (0.5)	0.036	0.64 (0.48)	0.48 (0.5)	0.007

COPD, chronic obstructive pulmonary disease; LLN, lower limit of normal; FVC, forced vital capacity; FEV!, forced expiratory volume in 1 second; RHSQ, Respiratory Health Screening Questionnaire; COPD-PS, chronic obstructive pulmonary disease-population screener; EGARPOC, COPD screening questionnaire from Terrassa; SD, standard deviation.

Figure 2. Diagram of the area under the ROC curve of the questionnaires and the FEV₁/FEV₆ of the portable spirometer; p < 0.0001.

Table 5. Evaluation of the properties of each cut-off of FEV₁/FEV₆ of the COPD-6 and those of the different questionnaires tested.

FEV1/FEV6 (%)	S	Sp	PPV	NPV	CC	AUC ROC
74	65.4	91	72.2	88.1	84.3	0.782 (0.724–0.840)
75	74.8	86.3	66.1	90.6	83.3	0.805 (0.752–0.859)
76	78.5	81.3	60	91.4	80.6	0.799 (0.747–0.851)
77	82.2	76.7	55.7	92.4	78.1	0.795 (0.744–0.845)
78	87.9	72.3	53.1	94.3	76.4	0.801 (0.754–0.848)
79	91.5	66.7	52.5	95.1	73.7	0.777 (0.729–0.824)
80	92.8	63.8	57.1	94.5	73.7	0.738 (0.688–0.789)
Questionnaires	S	Sp	PPV	NPV	CC	AUC ROC
RHSQ	73.8	56	37.4	85.7	60.7	0.718 (0.662–0.775)
COPD-PS	80.4	47.7	35.4	87.2	56.3	0.652 (0.596–0.709)
EGARPOC	72.9	58.3	38.4	85.8	62.2	0.678 (0.618–0.738)
Two questions	59.8	51.7	30.8	78.4	54.1	0.559 (0.496–0.622)

COPD diagnosed by fixed ratio.

COPD, chronic obstructive pulmonary disease; FVC, forced vital capacity; FEV₁, forced expìratory volume in 1 second; RHSQ, Respiratory Health Screening Questionnaire; COPD-PS, chronic obstructive pulmonary disease-population screener; EGARPOC, COPD screening questionnaire from Terrassa; S, sensitivity; Sp, specificity; PPV, positive predictive value; NPV, negative predictive value; AUC ROC, area under receiver operating characteristic curve.

Figure 3. Percentage of patients who are not diagnosed with COPD (undiagnosed patients) and the percentage of unnecessary spirometry performed (healthy) for the different cut-offs of the portable spirometer.

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