The chronic obstructive pulmonary disease assessment test improves the predictive value of previous exacerbations for poor outcomes in COPD

Figures & data

Figure 1 General outline of the study.

Table 1 Demographic, clinical characteristics and questionnaires’ scores

Variable	Overall population (N=497)	Composite event (no) (n=194)	Composite event (yes) (n=303)	P-value
Sex, male	446 (89.7%)	171 (88.1%)	273 (90.0%)	0.970
Age (years)	68.7 (9.2)	67.4 (9.3)	69.5 (9.1)	0.011
Body mass index (kg/m^2)	27.4 (5.0)	27.3 (5.2)	27.4 (4.9)	0.961
Active smokers	147 (29.6%)	70 (36.1%)	77 (25.4%)	0.061
Smoking habits (packs-years)	52.7 (30.5)	54.3 (27.7)	53.5 (32.1)	0.913
Cardiovascular risk
None	133 (26.7%)	54 (27.8%)	79 (26.1%)	0.581
Increased	127 (25.5%)	48 (24.7%)	79 (26.1%)
High	107 (21.5%)	36 (18.6%)	71 (23.4%)
Very high	124 (24.9%)	52 (28.8%)	72 (23.7%)
Missing data	6 (0.01%)	4 (0.02%)	2 (0.01%)
Diabetes mellitus	132 (26.6%)	63 (32.4%)	69 (22.7%)	0.117
Waist circumference (cm)	99.0 (18.6)	98.3 (19.9)	99.4 (17.7)	0.490
Time walking per day (minutes)	62.8 (88.0)	65.2 (80.4)	61.1 (92.8)	0.621
Time of COPD evolution (years)	10.2 (8.5)	9.7 (9.5)	10.6 (7.7)	0.282
Number of exacerbations in the previous year	2.9 (2.6)	2.3 (1.9)	3.3 (2.9)	<0.001
FVC (mL)	2,245 (1,050)	2,416 (1,064)	2,136 (1,028)	0.004
FVC (%)	67.8 (17.5)	70.6 (16.9)	66.1 (17.7)	0.006
FEV1 (mL)	1,141 (624)	1,282 (662)	1,052 (583)	<0.001
FEV1 (%)	47.1 (17.5)	50.7 (17.3)	45.4 (17.6)	0.001
FEV1/FVC (%)	51.2 (11.6)	52.9 (12.0)	50.8 (12.4)	0.069
CAT (units)	11.0 (8.0–16.0)	10.0 (7.0–15.0)	11.0 (9.0–15.0)	0.028
CCQ (units)	2.0 (1.3–2.8)	1.9 (1.1–2.7)	2.2 (1.5–2.8)	0.013
COPDSS (units)	11.0 (8.0–15.0)	10.9 (8.0–14.0)	12.3 (9.0–16.0)	0.001
AQ20 (units)	8.0 (5.0–11.0)	7.5 (4.0–10.0)	8.3 (5.0–11.0)	0.048

Notes: Values are expressed as mean (SD) and frequency (%). CAT, CCQ, COPDSS, and AQ20 questionnaires are expressed as median (interquartile range). P-value compares patients who suffered combined event with those who did not during the study follow-up.

Abbreviations: AQ20, Airways Questionnaire; CAT, COPD Assessment Test; CCQ, Clinical COPD Questionnaire; COPDSS, COPD Severity Score; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; SD, standard deviation.

Table 2 Incidence of exacerbations, death and combined event during the 1-year follow-up

	No of patients (%)	Annual incidence (95% CI)
Any severity of exacerbation	295 (59.4)	1.008 (0.899–1.126)
Ambulatory-treated exacerbations	210 (42.3)	0.610 (0.533–0.695)
Exacerbations requiring hospitalization	124 (24.9)	0.309 (0.259–0.366)
Exacerbations requiring emergency care	107 (21.5)	0.259 (0.214–0.310)
Mortality	21 (4.2)	0.044 (0.029–0.065)
Combined event	303 (61)	1.035 (0.925–1.155)

Abbreviations: CI, confidence interval; No, number.

Table 3 Univariate analysis of predictive value of CAT, CCQ, COPDSS, and AQ20 scores for composite event according to the best identified cutoffs

Variable	B	HR	95% CI	P-value
CAT ≥13.5	0.357	1.430	1.115–1.833	0.005
CCQ ≥2	0.310	1.364	1.063–1.749	0.015
COPDSS ≥9.5	0.132	1.141	0.877–1.484	0.32
AQ20 ≥8	0.270	1.310	1.020–1.683	0.035

Abbreviations: AQ20, Airways Questionnaire; B, beta coefficient; CAT, COPD Assessment Test; CCQ, Clinical COPD Questionnaire; CI, confidence interval; COPDSS, COPD Severity Score; HR, hazard ratio.

Table 4 Predictive value of CAT, CCQ, COPDSS, and AQ20 scores for composite event, categorized into two categories as indicated

Variable	B	HR	95% CI	P-value
CAT (<13.5 points and ≥13.5 points; n=497)
Age (years)	0.015	1.015	0.999–1.031	0.070
Smoking status (current vs former smoker RC)	−0.254	0.776	0.563–1.068	0.119
FEV1 (%)	−0.005	0.995	0.987–1.003	0.200
Waist circumference	0.001	1.001	0.994–1.008	0.722
Number of exacerbations in the previous year	0.056	1.058	1.018–1.100	0.004
Significant cardiovascular comorbidity	−0.061	0.941	0.682–1.299	0.712
CAT ≥13.5 points	0.334	1.396	1.076–1.812	0.012
CCQ (<2 points and ≥2 points; n=495)
≥Age (years)	0.015	1.015	0.999–1.031	0.072
≥Smoking status (current vs former smoker RC)	−0.232	0.793	0.574–1.095	0.159
FEV1 (%)	−0.005	0.995	0.987–1.003	0.210
Waist circumference	0.000	1.000	0.993–1.003	0.960
Number of exacerbations in the previous year	0.055	1.056	1.015–1.099	0.008
Significant cardiovascular comorbidity	−0.031	0.970	0.702–1.340	0.852
CCQ ≥2 points	0.167	1.182	0.902–1.549	0.226
COPDSS (<9.5 points and ≥9.5 points; n=497)
Age (years)	0.017	1.017	1.001–1.034	0.042
Sex (male vs female RC)	0.272	1.312	0.857–2.010	0.212
Smoking status (current vs former smoker RC)	−0.245	0.782	0.569–1.076	0.131
FEV1 (%)	−0.008	0.992	0.984–1.001	0.077
Number of exacerbations in the previous year	0.068	1.070	1.030–1.113	0.001
COPDSS ≥9.5 points	−0.092	0.912	0.672–1.238	0.555
AQ20 (<8 points and ≥8 points; n=497)
Age (years)	0.013	1.014	0.998–1.029	0.090
Smoking status (current vs former smoker RC)	−0.258	0.772	0.561–1.063	0.113
FEV1 (%)	−0.005	0.995	0.987–1.003	0.198
Waist circumference	0.000	1.000	0.993–1.007	0.952
Number of exacerbations in the previous year	0.058	1.060	1.019–1.102	0.004
AQ20 ≥8 points	0.150	1.161	0.892–1.512	0.267

Notes: Independent variables: age, sex, smoking status, FEV₁ (%), waist circumference, number of exacerbations in the previous year, significant cardiovascular comorbidity, and CAT ≥13.5 points. Dependent variable: combined event.

Abbreviations: AQ20, Airways Questionnaire; B, beta coefficient; CAT, COPD Assessment Test; CCQ, Clinical COPD Questionnaire; CI, confidence interval; COPDSS, COPD Severity Score; FEV₁, forced expiratory volume in 1 second; HR, hazard ratio; RC, reference category.

Figure 2 Kaplan–Meier curves comparing patients with CAT scores ≥13.5 points with those with CAT scores <13.5 points for the composite event.

Abbreviation: CAT, COPD Assessment Test.

Figure 3 ROC analysis derived from the Cox regression model in its capacity to predict combined event. This model includes the number of exacerbations in the previous year and CAT ≥13.5 points (AUC =0.864, P<0.001).

Abbreviations: ROC, receiver operating characteristic; CAT, COPD Assessment Test; AUC, area under the curve.