Interpretation of quality of life scores from the St George's Respiratory Questionnaire

M. Ferrer; C. Villasante; J. Alonso; V. Sobradillo; R. Gabriel; G. Vilagut; J.F. Masa; J.L. Viejo; C.A. Jiménez-Ruiz; M. Miravitlles

doi:10.1183/09031936.02.00213202

Tables

Table 1—

Characteristics of the general population weighted sample

Characteristics	All	M	F
Patients n	862	533	329
Sex
M	48.5
F	51.5
Age yrs
40–49	36.1	35.3	36.8
50–59	32.4	33.2	31.8
60–69	31.5	31.6	31.4
Education
High school or University	42.5	48.8	65.3
Primary school or no education	56.7	51.2	34.7
Social class (occupations)^#
I–II (professional/intermediate)	18.1	23.2	13.1
III (skilled nonmanual)	32.0	30.7	33.2
IV–V (manual)	49.8	40.1	53.7
Smoking behaviour
Never smoker	52.7	25.4	78.3
Former Smoker	24.1	41.5	7.8
Smoker>20 pack-yrs	13.1	24.1	2.9
Smoker⩽20 pack-yrs	10.0	9.0	10.9
Respiratory diseases
COPD	10.2	16.0	4.8
Asthma	3.6	3.8	3.4
Spirometric results
FVC mL	3454.5±877.7	4024.7±795.5	2916.9±552.2
FEV₁ mL	2578.6±726.4	2959.5±762.8	2219.5±459.7
% FVC over pred	90.3±13.8	87.0±13.8	93.5±13.1
% FEV₁ over pred	89.5±16.5	84.9±17.8	93.7±13.8
FEV₁/FVC %	99.2±11.1	96.6±12.0	101.6±9.4

Data are presented as % or mean±sd unless otherwise stated
M: male
F: female
COPD: chronic obstructive pulmonary disease
FVC: forced vital capacity
FEV₁: forced expiratory volume in one second
^#: social class based on an adaptation of the British General's Classification 26

Table 2—

Distribution characteristics and reliability estimates of the St George's Respiratory Questionnaire scales in the general population weighted sample

	Symptoms	Activity	Impacts	Overall
Mean	9.67	13.40	4.73	8.41
sd	13.24	17.63	9.92	11.33
Observed range	0–92.8	0–100	0–79.7	0–83.4
% With worst possible score (floor)	0.0	0.3	0.0	0.0
%With best possible score (ceiling)	41.2	43.5	59.5	21.1
% With missing data^#	2.0	7.6	9.6	13.2
% With missing score^¶	1.2	1.2	1.2	1.2
Cronbach's Alpha⁺
Probable case of COPD	0.77	0.90	0.89	0.95
Nonprobable case of COPD	0.73	0.84	0.87	0.91

Scale success rate %⁺
Probable case of COPD	81.3	84.4	92.3	88.0
Nonprobable case of COPD	87.5	71.9	94.2	86.0

n=862
COPD: chronic obstructive pulmonary disease
sd: standard deviation
COPD: chronic obstructive pulmonary disease
^#: percentage of individuals with at least one missing item
^¶: percentage of individuals with missing score after handling missing data recommended by authors was applied
⁺: calculated separately for probable and nonprobable cases of COPD by using Multitrait Analysis Program because it is not possible to apply weights with this package

Table 3—

Mean St George's Respiratory Questionnaire scale scores by demographical and clinical characteristics in the general population weighted sample

	Symptoms	Activity	Impacts	Overall
Sex
M	11.62	12.17	5.23	8.60
F	7.82	14.58	4.26	8.23
p‐value	<0.001	0.043	0.15	0.63
Age yrs
39–49	7.97	9.33	2.69	5.78
50–59	8.74	13.48	4.55	8.19
60–69	12.54	17.95	7.23	11.61
p‐value	<0.001	<0.001	<0.001	<0.001
Education
High school or more	8.54	9.26	3.10	6.05
Primary school or no education	10.45	16.53	6.02	10.20
p‐value	0.03	<0.001	<0.001	<0.001
Social class (occupations)^#
I‐II (professional/intermediate)	9.55	9.46	2.96	6.23
III (skilled nonmanual)	7.92	10.19	3.14	6.27
IV‐V (manual)	10.29	15.93	5.64	9.79
p‐value	0.07	<0.001	<0.001	<0.001
Smoking behaviour
Never smoker	7.49	13.63	4.16	7.81
Former smoker	9.58	13.19	5.50	8.69
Smoker⩽20 pack-yrs	12.99	11.58	3.38	7.76
Smoker>20 pack-yrs	16.12	14.20	6.59	10.76
p‐value	<0.001	0.74	0.04	0.09
% FEV₁ over pred
% FEV₁≥100	5.39	9.33	2.33	5.14
90⩽ % FEV₁<100	8.23	9.17	2.80	6.01
80⩽ % FEV₁<90	9.12	13.94	4.68	8.47
% FEV₁<80	16.20	21.14	9.27	14.30
p‐value	<0.001	<0.001	<0.001	<0.001

M: male
F: female
FEV₁: forced expiratory volume in one second. n=862
^#: social class based on an adaptation of the British Registrar General's Classification 26

Table 4—

Adjusted associations between St George's Respiratory Questionnaire total score (dependent variable) and respiratory disease-related variables in the general population weighted sample

	B	Beta	p‐value
COPD	1.22	0.03	0.40
Asthma	13.91	0.18	**
% FEV₁ over pred	−0.13	−0.21	**
Interaction of COPD and % FEV₁ over pred	−0.19	−0.11	**
Smoking behaviour
Never smoker
Former smoker	−0.08	0.00	0.91
Smoker≤20 pack-yrs	2.60	0.09	**
Smoker>20 pack-yrs	2.36	0.08	0.02
Sex	1.7	0.10	**
Age^#	0.1	0.11	**
Education	1.4	0.08	0.02
Interaction of age and asthma	1.2	0.13	**
Constant	5.0		**

B: non standardized coefficient
Beta: standardized coefficient
COPD: chronic obstructive pulmonary disease
% FEV₁ over pred: % force expiratory volume in one second over predicted n=862
^#: age-centred
Coefficient of determination: (R²)=0.19 (adjusted R²=0.18)
**: p<0.01

Table 5—

Percentiles (P) and means with standard deviation (sd) of the St George's Respiratory Questionnaire (SGRQ) scale scores by age

	40–49	50–59	60–69
Symptoms
P5	0.0	0.0	0.0
P10	0.0	0.0	0.0
P20	0.0	0.0	0.0
P30	0.0	0.0	4.42
P40	0.0	0.0	6.82
P50/median	4.24	6.88	11.88
P60	9.46	9.55	15.16
P70	12.17	12.71	23.43
P80	16.44	16.44	29.11
P90	25.32	32.48	42.30
P95	32.60	42.79	49.93
Mean±sd	8.83±12.41	10.34±14.35	16.13±16.77
Activity
P5	0.0	0.0	0.0
P10	0.0	0.0	0.0
P20	0.0	0.0	0.0
P30	0.0	0.0	0.0
P40	0.0	0.0	0.0
P50/median	0.0	5.97	11.16
P60	5.96	11.21	16.87
P70	11.21	17.32	22.60
P80	17.12	25.45	35.19
P90	23.13	36.93	47.69
P95	29.31	47.61	60.37
Mean±sd	7.76±11.15	12.69±16.59	16.28±20.41
Impacts
P5	0.0	0.0	0.0
P10	0.0	0.0	0.0
P20	0.0	0.0	0.0
P30	0.0	0.0	0.0
P40	0.0	0.0	0.0
P50/median	0.0	0.0	2.30
P60	0.0	3.55	4.77
P70	0.0	5.47	7.75
P80	5.03	9.22	16.01
P90	9.48	14.60	22.84
P95	15.10	22.27	38.77
Mean±sd	2.82±6.73	4.99±8.90	8.14±4.12
Total
P5	0.0	0.0	0.0
P10	0.0	0.0	0.0
P20	0.0	0.0	1.13
P30	1.65	2.08	2.08
P40	1.95	3.66	4.54
P50/median	2.72	5.48	6.98
P60	3.67	6.60	11.40
P70	6.56	8.75	14.13
P80	9.71	15.93	19.58
P90	11.65	23.34	30.64
P95	22.62	29.97	46.58
Mean±sd	5.49±7.72	8.41±10.74	12.17±14.89

Data are presented as SGRQ scale scores unless otherwise stated
Males from the general population weighted sample (n=533)

Table 6—

Percentiles (P) and means with standard deviation (sd) of the St George's Respiratory Questionnaire (SGRQ) scale scores by age

	40–49	50–59	60–69
Symptoms
P5	0.0	0.0	0.0
P10	0.0	0.0	0.0
P20	0.0	0.0	0.0
P30	0.0	0.0	0.0
P40	0.0	0.0	2.32
P50/median	4.42	4.24	4.42
P60	6.75	8.80	8.13
P70	8.80	9.69	9.54
P80	12.17	14.08	14.29
P90	18.79	19.28	28.18
P95	39.21	23.76	44.79
Mean±sd	7.24±10.85	7.09±8.88	9.24±3.43
Activity
P5	0.0	0.0	0.0
P10	0.0	0.0	0.0
P20	0.0	0.0	0.0
P30	0.0	0.0	0.0
P40	0.0	0.0	5.96
P50/median	5.25	6.21	12.19
P60	11.41	12.27	17.84
P70	17.12	23.28	29.31
P80	20.28	29.31	41.61
P90	35.17	35.47	47.69
P95	41.08	54.42	67.02
Mean±sd	10.81±13.99	14.29±17.43	19.36±22.62
Impacts
P5	0.0	0.0	0.0
P10	0.0	0.0	0.0
P20	0.0	0.0	0.0
P30	0.0	0.0	0.0
P40	0.0	0.0	0.0
P50/median	0.0	0.0	0.0
P60	0.0	3.55	3.55
P70	1.90	3.55	4.06
P80	4.06	7.17	8.35
P90	10.67	10.64	15.43
P95	14.38	20.43	43.03
Mean±sd	2.62±5.63	4.10±7.64	6.38±13.25
Total
P5	0.0	0.0	0.0
P10	0.0	0.0	0.0
P20	0.0	0.0	1.28
P30	0.80	1.78	2.17
P40	2.17	2.82	3.34
P50/median	3.75	4.44	4.26
P60	5.81	8.35	9.37
P70	7.38	10.92	13.28
P80	10.95	13.04	17.76
P90	15.40	17.93	25.96
P95	21.04	31.46	49.99
Mean±sd	6.09±7.41	7.97±9.35	11.05±14.83

Data are presented as SGRQ scale scores unless otherwise stated
Females from the general population weighted sample (n=329)

Table 7—

Distribution characteristics of the St George’s Respiratory Questionnaire (SGRQ) scores according to sex in the subsample of chronic obstructive pulmonary diseas (COPD) patients, participants with history of asthma and healthy group

	Symptoms	Activity	Impacts	Overall
Healthy individuals
M (n=143)	7.63±10.83 (6.28–8.99)	7.10±10.48 (5.78–8.41)	2.36±5.02 (1.73–2.99)	4.84±6.30 (4.05–5.63)
F (n=164)	6.49±9.57 (5.46–7.51)	13.13±15.73 (11.45–4.81)	3.47±7.66 (2.65–4.29)	7.14±8.83 (6.19–8.08)
p‐value^#	0.18	***	*	***
COPD Patients
M (n=275)	22.55±18.01 (18.28–26.82)	24.28±23.24 (18.75–29.81)	12.82±15.94 (9.03–6.60)	18.18±16.68 (14.21–22.15)
F (n=78)	12.43±13.9 (6.59–18.27)	19.52±25.45 (8.83–30.20)	8.05±13.11 (2.54–13.55)	12.55±15.61 (6.00–19.10)
p‐value^#	**	0.42	0.21	0.17
Asthma
M (n=39)	32.82±25.46 (20.34–45.28)	29.24±25.91 (16.56–41.92)	16.45±16.92 (8.16–24.74)	23.15±19.52 (13.6–2.70)
F (n=43)	26.34±20.42 (16.19–36.49)	29.53±26.69 (15.26–43.80)	15.61±19.53 (5.89–25.33)	21.68±20.68 (11.39–1.97)
p‐value^#	0.44	0.98	0.89	0.84

Data are presented as mean±sd (95% confidence interval) unless otherwise stated
M: male
F: female
COPD: chronic obstructive pulmonary disease
^#: comparison between SGRQ score from M and F
*: p<0.05
**: p<0.01
p<0.001