COPD classification models and mortality prediction capacity

Figures & data

Table 1 General characteristics of the cohort at baseline by mortality

Characteristics	Total (N=543)	Mortality		P-value
		Yes (n=167)	No (n=376)
Gender (male)	522 (96.1)	165 (98.9)	357 (94.9)	0.032
Age (years): $\overline{x}(\text{SD})$	68.3 (8.3)	72.3 (6.4)	66.6 (8.5)	<0.001
BMI (kg/m): $\overline{x}(\text{SD})$	28.3 (4.4)	27.9 (4.6)	28.4 (4.4)	0.252
Dyspnea (mMRC):$\overline{x}(\text{SD})$	24 (0.9)	1.37 (1.0)	2.2 (0.8)	<0.001
1	69 (12.7)	13 (7.8)	56 (14.9)
2	264 (48.6)	60 (37.7)	201 (53.5)
3	166 (30.6)	60 (35.9)	106 (28.2)
4–5	44 (8.1)	31 (18.6)	13 (3.5)
FEV1 (mL): $\overline{x}(\text{SD})$	1,464 (441.3)	1,248 (368)	1,560 (438)	<0.001
FEV1%: $\overline{x}(\text{SD})$	55.0 (13.3)	50.1 (13.7)	57.2 (12.6)	<0.001
Smoking status
Current smoker	114 (21.0)	24 (14.4)	90 (23.9)	0.02
Former smoker	414 (76.2)	140 (83.8)	274 (72.9)
No smoker	15 (2.8)	3 (1.8)	12 (3.2)
Packs/year: $\overline{x}(\text{SD})$	46.8 (27.3)	49.2 (27.5)	45.8 (27.2)	0.175
6-minute walking test (m): $\overline{x}(\text{SD})$	408.9 (92.4)	353.7 (99.8)	433.4 (77.3)	<0.001
Hospital admission for COPD in the 2 previous years
0	402 (74.0)	97 (58.1)	305 (81.1)	<0.001
1	87 (16.0)	40 (24.0)	47 (12.5)
≥2	54 (10.0)	30 (18.0)	24 (6.4)
Charlson comorbidity index: $\overline{x}(\text{SD})$	2.4 (1.4)	3.0 (1.7)	2.1 (1.2)	<0.001
0–1	172 (31.7)	33 (19.8)	139 (37.0)
2–3	264 (48.6)	77 (46.1)	187 (49.7)
>3	107 (19.7)	57 (34.1)	50 (13.3)
SGRQ (total): $\overline{x}(\text{SD})$	39.2 (20.1)	43.5 (19.6)	37.3 (20.0)	<0.001
Coronary artery disease	32 (5.9)	18 (10.8)	14 (3.7)	0.001
Congestive heart failure	79 (14.6)	50 (29.9)	29 (7.7)	<0.001
Angine	40 (7.4)	15 (9.0)	25 (6.6)	0.337
Arrhythmia	73 (13.4)	40 (24.0)	33 (8.8)	<0.001
Valvular heart disease	17 (3.1)	10 (6.0)	7 (1.9)	0.011
Hypertension	211 (38.9)	76 (45.5)	135 (35.9)	0.034
Peripheral artery disease	49 (9.0)	21 (12.6)	28 (7.4)	0.054
Cerebrovascular accident	39 (7.2)	13 (7.8)	26 (6.9)	0.717
Diabetes	88 (16.2)	36 (21.6)	52 (13.8)	0.024
Chronic renal failure	8 (1.5)	6 (3.6)	2 (0.5)	0.006
Liver disease	36 (6.6)	18 (10.8)	18 (4.8)	0.009

Abbreviations: BMI, body mass index; SGRQ, St George’s Respiratory Questionnaire.

Figure 1 Grouping of patients given by cluster classification depending on respiratory conditions (horizontal axes) and systemic conditions (vertical axes) based on multiple correspondence analyses.

Note: Mean and SD were included in the bubbles for age, BMI, FEV₁%, 6-minute WT, dyspnea and CCI, whereas the number of PH was described as the percentage of three or more.
Abbreviations: BMI, body mass index; CCI, Charlson comorbidity index; PH, previous hospitalizations; WT, walking test.

Table 2 Distribution of mortality by classification of patients based on different methods

Classification	Total	Mortality
		No	Yes
GOLD, n (%)
A	230 (42.4)	190 (82.6)	40 (17.4)
B	85 (15.6)	61 (71.8)	24 (28.2)
C	103 (19.0)	67 (65.1)	36 (34.9)
D	125 (23.0)	58 (46.4)	67 (53.6)
	AUC	0.678
GOLD2017, n (%)
A	298 (54.8)	237 (79.5)	61 (20.5)
B	154 (28.4)	97 (63.0)	57 (37.0)
C	35 (6.5)	20 (57.1)	15 (42.9)
D	56 (10.3)	22 (39.3)	34 (60.7)
	AUC	0.654
Cluster, n (%)
A	164 (30.2)	150 (91.5)	14 (8.5)
B	195 (35.9)	137 (70.3)	58 (29.7)
C	89 (16.4)	44 (49.4)	45 (50.6)
D	95 (17.5)	45 (47.4)	50 (52.6)
	AUC	0.722
BODE,a n (%)
0–2	260 (47.9)	213 (81.9)	47 (18.1)
3–4	193 (35.55)	130 (67.4)	63 (32.6)
5–6	71 (13.1)	31 (43.7)	40 (56.3)
7–10	19 (3.5)	2 (10.5)	17 (89.5)
	AUC	0.689

Note:

a BODE score was categorized as proposed by Celli et al (2004).³

Abbreviations: AUC, area under the curve; BODE, body mass index, obstruction, dyspnea and exercise.

Figure 2 ROC curves for various mortality prediction rules: cluster classification, GOLD_ABCD, GOLD₂₀₁₇ and BODE.

Notes: GOLD_ABCD, GOLD₂₀₁₇ and cluster classification were included in the original four categories, and BODE score was categorized into four categories as proposed by Celli et al.³ AUC and 95% CI were included for each of the classification rules.
Abbreviations: AUC, area under the curve; BODE, body mass index, obstruction, dyspnea and exercise; ROC, receiver operating characteristic.

Table 3 OR and its 95% CI obtained from a multiple logistic regression model including 5-year mortality as the outcome and various mortality prediction rules plus comorbidities as predictors

Scores and comorbidities	OR	95% CI	P-value
GOLD + comorbidities
GOLD
A	–	–
B	1.33	0.71, 2.48	0.37
C	1.95	1.11, 3.43	0.02
D	4.56	2.72, 7.62	<0.001
Coronary artery disease
No	–	–
Yes	2.70	1.23, 5.95	0.014
Congestive heart failure
No	–	–
Yes	2.82	1.58, 5.03	<0.001
Arrhythmia
No	–	–
Yes	2.10	1.16, 3.82	0.014
Chronic renal failure
No	–	–
Yes	7.29	1.23, 43.15	0.029
BODE + comorbidities
BODEa	1.59	1.40, 1.81	<0.001
Coronary artery disease
No	–	–
Yes	2.39	1.07, 5.37	0.034
Congestive heart failure
No	–	–
Yes	2.41	1.33, 4.37	0.004
Arrhythmia
No	–	–
Yes	2.32	1.27, 4.24	0.006
Chronic renal failure
No	–	–
Yes	5.649	1.06, 43.99	0.042

Notes:

a Raw BODE score, without any categorization. Only statistically significant comorbidities were maintained in the model.

Abbreviation: BODE, body mass index, obstruction, dyspnea and exercise.

Figure 3 ROC curves for various mortality prediction rules plus comorbidities: (A) GOLD; (B) BODE.

Notes: BODE index was included as continuous, without any categorization. AUC and 95% CI were included for each of the classification rules, with and without including comorbidities. The comorbidities included were cardiac arrest, cardiac congestive disease, arrhythmias and kidney disease.
Abbreviations: AUC, area under the curve; BODE, body mass index, obstruction, dyspnea and exercise; ROC, receiver operating characteristic.

CelliBRCoteCGMarinJMThe body-mass index, airflow obstruction, dyspnea, and exercise capacity index in chronic obstructive pulmonary diseaseN Engl J Med2004350101005101214999112

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