Table 2 Comparisons of characteristics of patients between readmission group and non-readmission group

Gender, n (%)

χ² = 2.208

 Male

425 (66.82)

292 (65.03)

133 (71.12)

 Female

211 (33.18)

157 (34.97)

54 (28.88)

Age, mean ± SD

70.82 ± 9.88

70.24 ± 9.73

72.21 ± 10.09

t =  − 2.295

BMI, mean ± SD

23.48 ± 2.95

23.50 ± 2.93

23.41 ± 2.99

t = 0.375

Acute exacerbation in previous 1 year, n (%)

χ² = 56.542

 No

430 (67.61)

344 (76.61)

86 (45.99)

 Yes

206 (32.39)

105 (23.39)

101 (54.01)

Smoking status, n(%)

Z =  − 1.393

 Never smoked

321 (50.47)

220 (49.00)

101 (54.01)

 Smoked before

93 (14.62)

64 (14.25)

29 (15.51)

 Smoker at present

222 (34.91)

165 (36.75)

57 (30.48)

  Daily amount of smoking, M (Q₁, Q₃)

0.00 (0.00, 15.00)

0.00 (0.00, 15.00)

0.00 (0.00, 10.00)

Z =  − 1.499

  Duration of smoking, M (Q₁, Q₃)

0.00 (0.00, 30.00)

0.00 (0.00, 30.00)

0.00 (0.00, 30.00)

Z =  − 1.496

  Number of years of smoking packets, M (Q₁, Q₃)

0.00 (0.00, 21.00)

0.00 (0.00, 25.00)

0.00 (0.00, 20.00)

Z =  − 1.597

LAMA, n(%)

χ² = 7.802

 No

479 (75.31)

352 (78.40)

127 (67.91)

  Yes

157 (24.69)

97 (21.60)

60 (32.09)

SAMA, n(%)

χ² = 0.410

 No

634 (99.69)

448 (99.78)

186 (99.47)

 Yes

2 (0.31)

1 (0.22)

1 (0.53)

LABA, n(%)

χ² = 16.741

 No

413 (64.94)

314 (69.93)

99 (52.94)

 Yes

223 (35.06)

135 (30.07)

88 (47.06)

SABA, n(%)

χ² = 0.993

 No

555 (87.26)

388 (86.41)

167 (89.30)

 Yes

81 (12.74)

61 (13.59)

20 (10.70)

PDE4I, n(%)

χ² = 0.045

 No

617 (97.01)

436 (97.10)

181 (96.79)

 Yes

19 (2.99)

13 (2.90)

6 (3.21)

ICS, n(%)

χ² = 11.089

 No

422 (66.35)

316 (70.38)

106 (56.68)

 Yes

214 (33.65)

133 (29.62)

81 (43.32)

Congestive heart-failure, n (%)

χ² = 0.399

 No

572 (89.94)

406 (90.42)

166 (88.77)

 Yes

64 (10.06)

43 (9.58)

21 (11.23)

Diabetes, n (%)

χ² = 0.008

 No

498 (78.30)

352 (78.40)

146 (78.07)

 Yes

138 (21.70)

97 (21.60)

41 (21.93)

Hypertension, n (%)

χ² = 1.650

 No

280 (44.03)

205 (45.66)

75 (40.11)

 Yes

356 (55.97)

244 (54.34)

112 (59.89)

Atrial fibrillation, n (%)

χ² = 0.197

 No

596 (93.71)

422 (93.99)

174 (93.05)

 Yes

40 (6.29)

27 (6.01)

13 (6.95)

Combined with other diseases, n (%)

χ² = 0.034

 No

432 (67.92)

304 (67.71)

128 (68.45)

 Yes

204 (32.08)

145 (32.29)

59 (31.55)

Systolic blood pressure, mean ± SD

133.46 ± 17.34

133.57 ± 17.48

133.18 ± 17.01

t = 0.258

Diastolic blood pressure, mean ± SD

78.73 ± 10.82

78.87 ± 10.99

78.40 ± 10.40

t = 0.496

Respiratory rate, mean ± SD

19.28 ± 2.53

19.20 ± 2.52

19.47 ± 2.53

t =  − 1.203

Temperature, mean ± SD

36.86 ± 0.56

36.87 ± 0.59

36.84 ± 0.46

t = 0.783

Heart rate, mean ± SD

81.65 ± 11.35

81.83 ± 11.85

81.22 ± 10.06

t = 0.616

Hb, mean ± SD

132.51 ± 17.26

132.80 ± 17.22

131.79 ± 17.32

t = 0.678

RBC, mean ± SD

4.33 ± 0.55

4.35 ± 0.56

4.28 ± 0.51

t = 1.386

WBC, M (Q₁, Q₃)

6.90 (5.53, 8.93)

6.89 (5.50, 8.83)

7.01 (5.71, 9.07)

Z = 0.922

PLT, M (Q₁, Q₃)

188.50 (151.75, 235.00)

190.00 (152.00, 234.00)

183.00 (149.50, 240.00)

Z =  − 0.627

NEUT, M (Q₁, Q₃)

4.68 (3.53, 6.65)

4.64 (3.43, 6.65)

4.96 (3.82, 6.62)

Z = 1.334

Percentage of neutrophils, mean ± SD

70.54 ± 11.65

70.20 ± 11.65

71.37 ± 11.60

t =  − 1.152

LYM, M (Q₁, Q₃)

1.29 (0.91, 1.80)

1.33 (0.92, 1.81)

1.23 (0.85, 1.67)

Z =  − 1.389

Percentage of lymphocytes, M (Q₁, Q₃)

19.42 (12.47, 27.13)

19.80 (13.30, 27.80)

17.60 (11.25, 25.25)

Z =  − 2.031

MONO, M (Q₁, Q₃)

0.44 (0.33, 0.60)

0.43 (0.33, 0.58)

0.48 (0.34, 0.67)

Z = 2.438

Percentage of monocytes, M (Q₁, Q₃)

6.30 (4.90, 8.00)

6.20 (4.90, 7.90)

6.50 (5.30, 8.30)

Z = 1.451

EOS, M (Q₁, Q₃)

0.10 (0.03, 0.19)

0.10 (0.03, 0.19)

0.10 (0.03, 0.19)

Z = 0.048

Percentage of eosinophils, M(Q₁, Q₃)

1.46 (0.40, 2.90)

1.47 (0.40, 2.90)

1.45 (0.40, 3.05)

Z = 0.007

RDW, Mean ± SD

13.20 ± 1.05

13.16 ± 1.03

13.29 ± 1.08

t =  − 1.342

ALT, M (Q₁, Q₃)

15.50 (11.00, 23.00)

16.22 (11.10, 25.00)

13.30 (9.80, 19.95)

Z =  − 3.176

AST, M (Q₁, Q₃)

18.00 (14.00, 23.10)

19.00 (14.70, 23.80)

16.50 (13.40, 21.30)

Z =  − 2.896

TBIL, M (Q₁, Q₃)

9.35 (6.70, 13.30)

9.60 (6.90, 13.60)

8.70 (6.35, 12.30)

Z =  − 1.947

ALB, Mean ± SD

39.89 ± 4.67

40.03 ± 4.73

39.55 ± 4.50

t = 1.198

BUN, M (Q₁, Q₃)

5.44 (4.45, 6.68)

5.45 (4.48, 6.66)

5.43 (4.39, 6.81)

Z = 0.053

Cr, M (Q₁, Q₃)

76.20 (64.40, 93.75)

75.40 (64.80, 90.90)

78.80 (63.70, 98.15)

Z = 1.099

Uric acid, M (Q₁, Q₃)

288.50 (226.00, 352.00)

292.00 (229.00, 351.00)

280.00 (224.50, 352.00)

Z =  − 0.121

Hypersensitive C-reactive protein, M (Q₁, Q₃)

8.40 (2.00, 36.67)

7.20 (2.00, 38.00)

9.70 (2.15, 33.20)

Z = 0.429

mMRC grade, n (%)

Z = 5.763

 0

1 (0.16)

0 (0.00)

1 (0.22)

 1

138 (21.70)

22 (11.76)

116 (25.84)

 2

279 (43.87)

73 (39.04)

206 (45.88)

 3

189 (29.72)

75 (40.11)

114 (25.39)

 4

29 (4.56)

17 (9.09)

12 (2.67)

CAT score, Mean ± SD

20.28 ± 5.34

19.55 ± 5.02

22.04 ± 5.67

t =  − 5.475

FEV₁, M (Q₁, Q₃)

1.60 (1.10, 2.21)

1.62 (1.12, 2.21)

1.60 (1.05, 2.19)

Z =  − 0.504

FVC, M (Q₁, Q₃)

2.26 (1.66, 3.64)

2.20 (1.65, 3.45)

2.34 (1.70, 3.83)

Z = 1.379

FEV1/FVC, Mean ± SD

67.25 ± 13.27

68.87 ± 13.48

63.36 ± 11.88

t = 4.845

FEV₁ in predicted value FEV₁, mean ± SD

56.81 (42.65, 67.80)

58.40 (43.70, 68.42)

52.60 (38.80, 65.70)

Z =  − 3.076

Use of systemic glucocorticoid, n (%)

χ² = 6.465

 No

472 (74.21)

346 (77.06)

126 (67.38)

 Yes

164 (25.79)

103 (22.94)

61 (32.62)

Antibacterial agents, n (%)

χ² = 0.012

 No

13 (2.04)

9 (2.00)

4 (2.14)

 Yes

623 (97.96)

440 (98.00)

183 (97.86)

Oxygen therapy, n (%)

χ² = 3.903

 No

126 (19.81)

98 (21.83)

28 (14.97)

 Yes

510 (80.19)

351 (78.17)

159 (85.03)

Mechanical ventilation, n (%)

χ² = 4.276

 No

628 (98.74)

446 (99.33)

182 (97.33)

 Noninvasive ventilation

8 (1.26)

3 (0.67)

5 (2.67)