Characteristics of 12-Month Readmission for Hospitalized Patients with COPD: A Propensity Score Matched Analysis of Prospective Multicenter Study

Figures & data

Figure 1 Flowchart of cohort selection.

Note: Severe exacerbation indicates patients experienced readmission for exacerbations.

Abbreviation: COPD, chronic obstructive pulmonary disease.

Figure 2 The number of recruited patients over time.

Abbreviation: COVID-19, coronavirus disease 2019.

Figure 3 Number of patients from 27 study centers in China.

Table 1 Demographic and Clinical Data of Cohort Patients

Variable	Missing	Full Cohort
Number		465
Age -yr		70.1±9.3
Male sex -no. (%)		409(88)
Body-mass index -kg/m^2	1	22.81±3.67
Smoking status -no. (%)
Non-smoker		131(28.3)
Current smoker		101(21.7)
Ex-smoker		233(50.0)
Pack-years of smoking		40.92±23.77
Time since COPD diagnosis - yr		9.27±9.36
Severe exacerbations in the following 12 months -no. (%)		193(41.5)
Symptoms -no. (%)
Dyspnea		310(66.7)
Wheezing		220(47.3)
Cough		280(60.2)
Sputum Production		259(55.7)
COPD Assessment Test score	13	18±6.9
FEV1/FVC		53.15±12.16
FEV1 -% predicted		44.14±17.31
FVC -% predicted		63.28±18.64
Blood eosinophil percentage -median (IQR)	6	1.71(3.07)
Comorbidities -no. (%)	45
Cor pulmonale		25(5.38)
Osteoporosis		7(1.51)
Depression		2(0.43)
Hypertension		183(39.4)
Diabetes		46(9.9)
COPD inhaled treatment -no. (%)	28
LAMA		46(9.9)
LABA plus LAMA		12(2.6)
LABA plus ICS		112(24.1)
LABA plus LAMA plus ICS		137(29.5)
Others		7(1.5)
Non-pharmacological treatments
Flu, pneumonia vaccine		23(4.9)
Long-term oxygen therapy		27(5.8)
Contracted lips or abdominal breathing		7(1.5)

Notes: The body-mass index is the weight in kilograms divided by the square of the height in meters. The blood eosinophil percentage is of total leukocyte count. Scores on the COPD Assessment Test range from 0 to 40, with higher scores indicating more symptoms.

Abbreviations: yr, the year; no, number; COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in one second; FVC, forced vital capacity ratio; FEV1 -% predicted, FEV1 of the predicted normal value; FVC -% predicted, FVC of the predicted normal value; IQR, interquartile range; LAMA, long-acting antimuscarinic antagonist; LABA, long-acting beta₂-agonists; ICS, inhaled corticosteroids.

Table 2 Characteristics of Patients with or Without Severe Exacerbations, Before and After 1:1 Propensity Score Matching

Variable	Unmatched Patients			Propensity-Score-Matched Patients
	Severe Exacerbations	Non-Severe Exacerbations	P-value	Severe Exacerbations	Non-Severe Exacerbations	P-value
Number	193(41.5)	272(58.5)		172	172
Age - yr	71.53±8.93	69.13±9.38	0.006	71.1±9.09	70.8±7.92	0.738
Male sex - no. (%)	167(86.5)	242(89.0)	0.425	147(85.5)	147(85.5)	1.000
Body-mass index- kg/m2	22.88±4.08	22.77±3.36	0.760	22.97±3.8	22.95±3.55	0.481
Residence			0.009			0.887
Urban	81(42.4)	144(54.8)		79(45.9)	77(44.8)
Rural	110(57.6)	119(45.2)		91(52.9)	92(53.5)
Smoking status - no. (%)			<0.001			0.969
Non-smoker	55(28.5)	76(27.9)		51(29.7)	53(30.8)
Current smoker	26(13.5)	75(27.6)		26(15.1)	25(14.5)
Ex-smoker	112(58.0)	121(44.5)		95(55.2)	94(54.7)
Pack-years of smoking	42.79±22.24	39.59±24.77	0.230	41.74±21.13	40.31±26.83	0.649
Time since COPD diagnosis - yr	13.16±11.52	7.11±8.33	<0.001	13.06±11.12	7.75±7.32	<0.001
Symptoms - no. (%)
Dyspnea	112(58.0)	108(39.7)	<0.001	100(58.1)	72(41.3)	<0.001
Cough	132(68.4)	148(54.4)	<0.001	117(68.0)	54(31.4)	<0.001
Sputum production	121(62.7)	138(50.7)	<0.001	107(62.2)	89(51.7)	<0.001
COPD Assessment Test score	20.3±6.5	16.3±6.7	<0.001	20.23±6.48	16.8±6.9	<0.001
FEV1- % predicted	41.45±17.00	46.05±17.32	0.005	43.07±17.09	43.27±16.47	0.911
Severity (% pre FEV1) - no. (%)			0.034			0.994
Mild (≥80%)	6(3.1)	13(4.8)		6(3.5)	7(4.1)
Moderate (≥50% and <80%)	43(22.3)	84(30.9)		43(25.1)	43(25.1)
Severe (≥30%s and <50%)	88(46.6)	127(46.7)		83(48.5)	83(48.5)
Very severe (<30%)	54(28)	46(16.9)		39(22.8)	39(22.8)
FVC- % predicted	61.24±18.98	64.73±18.30	0.048	63.01±18.45	61.89±16.83	0.558
Blood eosinophil percentage-median (IQR)	1.51(3.16)	2.08(3.29)	0.002	1.5(3.18)	2.03(3.78)	0.047
Eos≥2% - no. (%)	74(38.5)	138(51.7)	0.005	68(29.8)	86(50.9)	0.039
Eos<2% - no. (%)	118(61.5)	129(48.3)		103(60.2)	83(49.1)
Comorbidities - no. (%)
Cor pulmonale	18(11.3)	7(3.6)	0.005	15(10.6)	6(4.6)	0.064
Osteoporosis	4(2.5)	3(1.5)	0.781	4(2.8)	2(1.5)	0.754
Depression	1(0.6)	1(0.5)	0.696	1(0.7)	1(0.7)	0.954
Hypertension	85(53.8)	97(49.2)	0.396	77(54.2)	68(51.9)	0.702
Diabetes	21(13.1)	25(12.7)	0.903	17(12.0)	19(14.5)	0.537
Cardiovascular disease	19(11.9)	16(8.1)	0.236	17(12.0)	8(6.1)	0.093
Cerebrovascular disease	18(11.3)	15(7.6)	0.238	16(11.3)	9(6.9)	0.208
Regular inhaler - no. (%)	128(66.3)	118(43.4)	<0.001	114(66.3)	83(48.3)	<0.001
COPD inhaled treatment - no. (%)
LAMA	19(9.8)	27(9.9)	0.977	19(11.0)	16(9.3)	0.593
LABA+LAMA	2(1.0)	10(3.7)	0.141	1(0.6)	2(1.2)	0.562
ICS+LABA	59(30.6)	55(20.2)	0.011	54(31.4)	38(22.1)	0.051
ICS+LABA+LAMA	69(35.8)	68(25.0)	0.012	60(34.9)	42(24.4)	0.034
Others	3(1.6)	4(1.5)	1.000	2(1.2)	2(1.2)	1.000

Note: Severity (% pre FEV1) indicates the classification of airflow limitation of severity in COPD based on GLOD 2019 document.

Abbreviations: yr, the year; no, number; COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in one second; FVC, forced vital capacity ratio; FEV1- % predicted, FEV1 of the predicted normal value; FVC- % predicted, FVC of the predicted normal value; IQR, interquartile range; Eos, eosinophil; LAMA, long-acting antimuscarinic antagonist; LABA, long-acting beta2-agonists; ICS, inhaled corticosteroids.

Table 3 Multivariate Regression Analysis of Associations with Severe Exacerbation (Group A)

Variable	Unmatched			Propensity Score Matched
	OR	95% CI	P-value	OR	95% CI	P-value
Time since COPD diagnosis (reference: <9yr)	2.91	1.96–4.31	<0.001	2.16	1.38–3.39	<0.001
CAT score (reference: <10)	4.36	1.96–9.72	<0.001	3.40	1.36–8.51	0.009
Blood eosinophil percentage (reference: ≥2%)	1.72	1.15–2.56	0.008	1.68	1.07–2.64	0.025
Cor pulmonale (reference: no)	2.56	1.00–6.56	0.05			NS

Abbreviations: yr, the year; no, number; COPD, chronic obstructive pulmonary disease; CAT, the COPD Assessment Test; OR, odds ratio; CI, confidence internal; NS, not significant.

Table 4 The Goodness of Fit and Accuracy of the Model

	AUC	95% CI	P-value	Sensitivity	Specificity	H-L Test	Omnibus
Unmatched	0.727	0.681–0.773	<0.001	77.2	59.93	0.728	<0.001
Matched	0.662	0.605–0.720	<0.001	55.81	68.02	0.837	<0.001

Abbreviations: AUC, area under the curve; CI, confidence interval; H-L, Hosmer-Lemeshow test.

Figure 4 Receiver operating characteristic (ROC) curve for 12-month readmission of severe exacerbations using data from logistic model before propensity-score matching.

Abbreviation: AUC, area under the curve.

Figure 5 Receiver operating characteristic (ROC) curve for 12-month readmission of severe exacerbations using data from logistic model after propensity-score matching.

Abbreviation: AUC, area under the curve.