Validation and reproducibility of the lung function questionnaire (LFQ) for the diagnosis of COPD in Colombia

	Total population, n = 1559	Without COPD, n = 1259	With COPD, n = 340	p-value
Weight, kg, n (SD)	70.6 (13.74)	71.4 (13.86)	67.7 (12.86)	<0.001
Height, cm, n (SD)	159.6 (9.25)	159.6 (9.29)	159.7 (9.10)	0.954
Pulmonary function, L (SD)
FVC reference	3.1 (0.81)	3.1 (0.82)	3.0 (0.8)	0.014
FVC pre-B2	2.9 (0.98)	3.0 (0.99)	2.7 (0.92)	<0.001
FVC pre-B2, % predicted	94.7 (21.33)	96.3 (20.76)	88.8 (22.36)	<0.001
FVC post-B2	3.0 (0.97)	3.1 (0.97)	2.9 (0.97)	0.001
FVC post-B2, % predicted	98.1 (21.02)	98.7 (20.48)	95.8 (22.77)	0.031
FVC, % change	4.2 (7.97)	2.9 (6.75)	9.1 (9.98)	0.001
FEV1 reference	2.4 (0.67)	2.5 (0.67)	2.3 (0.64)	<0.001
FEV1 pre-B2, best	2.2 (0.82)	2.4 (0.77)	1.5 (0.61)	<0.001
FEV1 pre-B2, % predicted	90.6 (25.02)	97.0 (21.69)	66.6 (21.81)	<0.001
FEV1 post-B2, best	2.3 (0.82)	2.5 (0.78)	1.7 (0.64)	<0.001
FEV1 post-B2, % predicted	96.4 (9.96)	102.2 (21.31)	74.9 (22.40)	<0.001
FEV1, % change	7.9 (9.96)	6.0 (7.26)	14.9 (14.5)	<0.001
FEV/FVC reference	78.2 (4.78)	78.9 (3.16)	75.7 (7.90)	<0.001
FEV/FVC pre-B2%, best	74.6 (12.79)	79.4 (7.83)	56.7 (11.73)	<0.001
FEV/FVC pre-B2, % predicted	94.9 (11.45)	100.7 (9.17)	73.7 (73.66)	<0.001
FEV/FVC post-B2%, best	76.8 (12.4)	81.7 (6.86)	58.6 (11.32)	<0.001
FEV/FVC post-B2, % predicted	98.0 (15.41)	103.7 (9.01)	76.5 (15.37)	<0.001

Validity analysis of the LFQ questionnaire with diagnosis of COPD

	S	95% CI	E	95% CI	VPP	95% CI	VPN	95% CI	LR+	95% CI	LR–	95% CI	Index of accuracy	Youden's index	NND	NNMD
Total population	91.18	88.0–94.3	32.41	29.8–35.0	26.70	24.1–29.3	93.15	90.7–95.6	1.34	1.28–1.42	0.27	0.19–0.39	0.44	0.23	4	2
Without symptoms	80.77	63.7–97.8	62.91	56.2–69.6	21.00	12.5–29.5	96.40	92.9–99.9	2.17	1.69–2.81	0.3	0.14–0.68	0.64	0.43	2	3
With symptoms	92.04	88.9–95.2	26.20	23.5–28.9	27.24	24.5–29.9	91.64	88.3–94.9	1.24	1.19–1.31	0.3	0.21–0.45	0.41	0.18	5	2
No smoking	85.00	79.2–90.9	43.20	39.5–46.9	25.33	21.6–29.1	92.71	89.7–95.7	1.49	1.37–1.64	0.34	0.24–0.51	0.5	0.28	4	2
Smoking	96.67	93.7–99.6	18.63	15.3–21.9	27.88	24.3–31.5	94.50	89.8–99.2	1.18	1.13–1.25	0.17	0.08–0.40	0.37	0.15	7	2
No exposure to wood smoke	87.62	80.8–94.4	36.62	32.5–40.7	20.67	16.8–24.6	94.01	90.6–97.4	1.38	1.26–1.52	0.33	0.20–0.57	0.44	0.24	4	2
Exposure to wood smoke	92.77	89.2–96.3	29.06	25.6–32.5	30.45	27.0–33.9	92.31	88.6–96.1	1.3	1.23–1.39	0.24	0.16–0.40	0.45	0.21	5	2
Without smoker in the home	91.35	87.8–94.9	34.62	31.5–37.8	29.00	25.9–32.1	93.20	90.4–96.0	1.39	1.32–1.48	0.24	0.17–0.37	0.47	0.25	4	2
With smoker in the home	90.00	81.6–98.4	28.64	22.2–36.0	26.87	20.5–33.2	90.77	82.9–98.6	1.26	1.12–1.42	0.34	0.16–0.77	0.42	0.18	5	2
Without smoking and without exposure to wood smoke	76.19	62.1–90.3	47.74	41.8–53.7	17.58	11.8–23.4	93.20	88.8–97.6	1.45	1.19–1.78	0.49	0.29–0.87	0.92	0.23	4	14
With smoking and exposure to wood smoke	97.44	94.1 – 100	12.72	8.7–16.8	31.58	26.7–36.5	92.31	82.7–100	1.11	1.06–1.18	0.2	0.06–0.64	0.37	0.1	10	2
Without symptoms	80.77	63.7–97.8	62.91	56.2–69.6	21.00	12.5–29.5	96.40	92.9–99.9	2.17	1.69–2.81	0.3	0.14–0.68	0.64	0.43	2	3
No exposure to wood smoke	87.62	80.8–94.4	36.62	32.5–40.7	20.67	16.8–24.6	94.01	90.6–97.4	1.38	1.26–1.52	0.33	0.20–0.57	0.44	0.24	4	2

Results of the correlation analysis and concordance using LFQ questionnaire

	Correlation coefficient	95% CI	p-value
t-tests for related samples			0.793
Pearson's correlation coefficient	0.884		<0.001
Spearman's correlation coefficient	0.881		<0.001
ICC	0.884	0.863–0.901	<0.001
Cronbach's alpha	0.938
Kappa correlation coefficient	0.797		<0.001
ICC FEV1 pre, L, vs LFQ	0.165	0.117–0.212	<0.001
ICC FEV1 post, L, vs LFQ	0.158	0.110–0.206	<0.001
ICC FEV1/FVC pre, L, vs LFQ	0.179	0.131–0.226	<0.001
ICC FEV1/FVC post, L, vs LFQ	0.183	0.135–0.230	<0.001

Results of the LFQ questionnaire in the general population and in patients with and without COPD

	Total population, n = 1599	Without COPD, n = 1259	With COPD, n = 340	p-value
How often do you have a cough with mucus?
Never, n (SD)	348 (21.76)	298 (23.6)	50 (14.7)	<0.001
Rarely, n (SD)	591 (36.96)	481 (38.2)	110 (32.3)
Sometimes, n (SD)	351 (21.95)	274 (21.7)	77 (22.64)
Frequently, n (SD)	208 (13)	141 (11.1)	67 (19.7)
Very often, n (SD)	101 (6.3)	65 (5.16)	36 (10.58)
How often do you fee sounds in your chest (gasps, whistles or vibrations) when you breathe?
Never, n (SD)	664 (41.5)	583 (46.3)	81 (23.82)	<0.001
Rarely, n (SD)	310 (19.38)	253 (20.1)	57 (16.76)
Sometimes, n (SD)	366 (22.88)	260 (20.6)	106 (31.1)
Frequently, n (SD)	169 (10.56)	111 (8.81)	58 (17.05)
Very often, n (SD)	90 (5.62)	52 (4.13)	38 (11.17)
How often are you short of breath during a physical activity (when climbing stairs or climbing a slope without resting)?
Never, n (SD)	324 (21.6)	272 (21.6)	52 (15.29)	<0.001
Rarely, n (SD)	228 (14.25)	188 (14.9)	40 (11.76)
Sometimes, n (SD)	361 (22.57)	304 (24.1)	57 (17.76)
Frequently, n (SD)	378 (23.63)	291 (23.1)	87 (25.58)
Very often, n (SD)	308 (19.26	203 (16.2)	104 (30.5)
How many years have you smoked?
I have never smoked, n (SD)	872 (54.5)	710 (56.39)	162 (47.6)	<0.001
≤10 years, n (SD)	244 (15.25)	210 (16.67)	34 (10)
11–20 years, n (SD)	149 (9.31)	119 (9.45)	30 (8.82)
21–30 years, n (SD)	107 (6.69)	76 (6.03)	31 (9.11)
>30 years, n (SD)	227 (14.19)	144 (11.43)	83 (24.41)
How old are you?
<40 years, n (SD)	15 (0.93)	15 (1.19)	0 (0)	<0.001
40–49 years, n (SD)	197 (12.32)	176 (13.97)	21 (6.17)
50–59 years, n (SD)	320 (20.01)	285 (822.63)	35 (10.29)
60–69 years, n (SD)	483 (30.2)	387 (30.73)	96 (28.23)
≥70 years, n (SD)	584 (36.52)	396 (31.45)	188 (55.29

Total LFQ score, n (SD)	16.2 (3.52)	16.8 (3.34)	14.1 (3.35)	<0.001
LFQ development time, n (SD)	0.9 (0.82)	0.9 (0.87)	0.8 (0.64)	0.323
LFQ score ≤18, n (SD)	1161 (0.72)	851 (9.67)	310 (0.91)	<0.001
LFQ score ≤18 without respiratory symptoms, n (SD)	100 (0.41)	79 (0.37)	21 (0.80)	<0.001
LFQ score ≤18 with respiratory symptoms, n (SD)	1061 (0.78)	772 (0.73)	289 (0.92)	<0.001
LFQ score ≤18 without smoking, n (SD)	537 (0.62)	401 (0.56)	136 (0.85)	<0.001
LFQ score ≤18 with smoking, n (SD)	624 (0.85)	450 (0.81)	174 (0.96)	<0.001
LFQ score ≤18 no exposure to wood smoke, n (SD)	445 (0.67)	353 (0.63)	92 (0.87)	<0.001
LFQ score ≤18 exposure to wood smoke, n (SD)	716 (0.76)	498 (0.70)	218 (0.92)	<0.001
LFQ score ≤18 no smoker in the house, n (SD)	838 (0.75)	595 (0.65)	243 (0.91)	<0.001
LFQ score ≤18 with smoker in the house, n (SD)	201 (0.75)	147 (0.71)	54 (0.9)	0.003
LFQ score ≤18 no smoking or exposure to wood smoke, n (SD)	182 (055)	150 (0.52)	32 (0.76)	0.004
LFQ score ≤18 with smoking and exposure to wood smoke, n (SD)	361 (0.90)	247 (0.87)	114 (0.97)	0.002

General characteristics of the population

	Total population, n = 1599	Without COPD, n = 1259	With COPD, n = 340	p-value
Age, in years, n (SD)	65.3 (11.9)	64 (11.88)	70 (11.03)	<0.001
Male sex, n (%)	702 (49.9)	518 (41.1)	184 (54.1)	<0.001
Race, n (%)
White	196 (12.2)	153 (12.1)	43 (12.5)	0.354
Half-blood	1381 (86.4)	1086 (86.2)	295 (86.7)
Black	4 (3)	3 (2.3)	1 (0.2)
Other	3 (1)	2 (0.2)	1 (0.2)
Educational level, n (SD)
None	20 (1.2)	15 (1.2)	5 (1.4)	<0.001
Primary	604 (37.7)	425 (33.7)	179 (52.6)
High school	427 (26.7)	356 (28.2)	71 (20.8)
Technologist	12 (0.77)	11 (0.9)	1 (0.2)
Technical	121 (9.3)	29 (9.6)	150 (8.5)
Master's degree	5 (0.3)	2 (0.1)	3 (0.8)
Doctorate	4 (0.2)	4 (0.3)	0 (0)
Years of study, n (SD)	9.3 (5.6)	9.8 (5.56)	7.5 (5.51)	<0.001
Respiratory symptoms, n (%)	1360 (85)	1046 (83)	314 (90)	<0.001
Age at onset of symptoms, n (SD)	57.3 (17.21)	57 (16.11)	57.5 (20.05)	0.856
Smoking, n (%)	733 (45)	553 (43)	180 (52)	0.003
IPA, n (%)	15.2 (23.26)	12.8 (21.25)	22.6 (27.43)	<0.001
Passive smoker, n (%)	266 (16)	206 (16.2)	60 (17.6)	0.982
Exposure to wood smoke, n (%)	937 (58)	702 (55.8)	235 (69.1)	<0.001
Prior diagnosis of COPD, n (%)	409 (25)	246 (19.5)	163 (47.9)	<0.001
Prior diagnosis of asthma, n (%)	215 (13)	149 (11.8))	66 (19.4)	<0.001

AUC of the LFQ questionnaire for COPD diagnosis

	AUC	95% CI	p-value
Total population of the study	0.715	0.685–0.745	<0.001
Population without evidence of respiratory symptoms	0.798	0.706–0.889	<0.001
Population with respiratory symptoms	0.694	0.661–0.727	<0.001
Population without a history of smoking	0.713	0.670–0.757	<0.001
Population with a history of smoking	0.706	0.664–0.748	<0.001
Population without a history of exposure to wood smoke	0.715	0.661–0.770	<0.001
Population with a history of exposure to wood smoke	0.705	0.668–0.742	<0.001
Population without a history of smoking at home	0.73	0.697–0.763	<0.001
Population with a history of smoking at home	0.653	0.581–0.773	<0.001
Population without smoking and without exposure to wood smoke	0.671	0.581–0.760	<0.001
Population with smoking and exposure to wood smoke	0.674	0.617–0.730	<0.001

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Validation and reproducibility of the lung function questionnaire (LFQ) for the diagnosis of COPD in Colombia

Article Category: Original Papers

Publicado en línea: 27 jul 2020

Páginas: 37 - 46

DOI: https://doi.org/10.2478/pneum-2020-0010

Palabras clavechronic obstructive pulmonary disease, spirometry, interview and questionnaires, validity and reproducibility

© 2020 Alirio Rodrigo Bastidas Goyes et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

General lung function characteristics of the population

Validity analysis of the LFQ questionnaire with diagnosis of COPD

Results of the correlation analysis and concordance using LFQ questionnaire

Results of the LFQ questionnaire in the general population and in patients with and without COPD

General characteristics of the population

AUC of the LFQ questionnaire for COPD diagnosis

Palabras clave
chronic obstructive pulmonary disease, spirometry, interview and questionnaires, validity and reproducibility