Table 4 The equilibrium test of training set and testing set

Gender, n (%)

χ² = 0.383

 Male

425 (66.82)

294 (66.07)

131 (68.59)

 Female

211 (33.18)

151 (33.93)

60 (31.41)

Age, Mean ± SD

70.82 ± 9.88

70.62 ± 9.91

71.27 ± 9.80

t =  − 0.757

BMI, Mean ± SD

23.48 ± 2.95

23.42 ± 3.01

23.61 ± 2.79

t =  − 0.750

Acute exacerbation in previous 1 year, n (%)

χ² = 1.740

 No

430 (67.61)

308 (69.21)

122 (63.87)

 Yes

206 (32.39)

137 (30.79)

69 (36.13)

Smoking status, n(%)

Z = 0.336

 Never smoked

321 (50.47)

229 (51.46)

92 (48.17)

 Smoked before

93 (14.62)

59 (13.26)

34 (17.80)

 Smoker at present

222 (34.91)

157 (35.28)

65 (34.03)

  Daily amount of smoking, M (Q₁, Q₃)

0.00 (0.00, 15.00)

0.00 (0.00, 12.00)

0.00 (0.00, 15.00)

Z =  − 0.135

  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 =  − 0.243

 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 =  − 0.133

LAMA, n(%)

χ² = 1.067

 No

479 (75.31)

330 (74.16)

149 (78.01)

 Yes

157 (24.69)

115 (25.84)

42 (21.99)

SAMA, n(%)

χ² = 0.861

 No

634 (99.69)

443 (99.55)

191 (100.00)

 Yes

2 (0.31)

2 (0.45)

0 (0.00)

LABA, n(%)

χ² = 0.035

 No

413 (64.94)

290 (65.17)

123 (64.40)

 Yes

223 (35.06)

155 (34.83)

68 (35.60)

SABA, n(%)

χ² = 0.189

 No

555 (87.26)

390 (87.64)

165 (86.39)

 Yes

81 (12.74)

55 (12.36)

26 (13.61)

PDE4I, n(%)

χ² = 0.129

 No

617 (97.01)

431 (96.85)

186 (97.38)

 Yes

19 (2.99)

14 (3.15)

5 (2.62)

ICS, n(%)

χ² = 0.101

 No

422 (66.35)

297 (66.74)

125 (65.45)

 Yes

214 (33.65)

148 (33.26)

66 (34.55)

Congestive heart-failure, n (%)

χ² = 0.004

 No

572 (89.94)

400 (89.89)

172 (90.05)

 Yes

64 (10.06)

45 (10.11)

19 (9.95)

Diabetes, n (%)

χ² = 2.515

 No

498 (78.30)

356 (80.00)

142 (74.35)

 Yes

138 (21.70)

89 (20.00)

49 (25.65)

Hypertension, n (%)

χ² = 0.507

 No

280 (44.03)

200 (44.94)

80 (41.88)

 Yes

356 (55.97)

245 (55.06)

111 (58.12)

Atrial fibrillation, n (%)

χ² = 0.124

 No

596 (93.71)

418 (93.93)

178 (93.19)

 Yes

40 (6.29)

27 (6.07)

13 (6.81)

Combined with other diseases, n (%)

χ² = 1.130

 No

432 (67.92)

308 (69.21)

124 (64.92)

 Yes

204 (32.08)

137 (30.79)

67 (35.08)

Systolic blood pressure, Mean ± SD

133.46 ± 17.34

132.66 ± 16.44

135.31 ± 19.16

t =  − 1.665

Diastolic blood pressure, Mean ± SD

78.73 ± 10.82

78.21 ± 10.42

79.95 ± 11.62

t =  − 1.859

Respiratory rate, Mean ± SD

19.28 ± 2.53

19.17 ± 2.41

19.52 ± 2.77

t =  − 1.604

Temperature, Mean ± SD

36.86 ± 0.56

36.85 ± 0.54

36.90 ± 0.60

t =  − 1.055

Heart rate, Mean ± SD

81.65 ± 11.35

81.40 ± 11.24

82.24 ± 11.60

t =  − 0.860

Hb, Mean ± SD

132.51 ± 17.26

132.36 ± 17.41

132.85 ± 16.88

t =  − 0.328

RBC, Mean ± SD

4.33 ± 0.55

4.32 ± 0.55

4.35 ± 0.54

t =  − 0.654

WBC, M (Q₁, Q₃)

6.90 (5.53, 8.93)

6.85 (5.53, 8.68)

7.18 (5.50, 9.64)

Z = 1.141

PLT, M (Q₁, Q₃)

188.50 (151.75, 235.00)

189.00 (155.00, 234.00)

187.00 (144.50, 239.00)

Z =  − 0.845

NEUT, M (Q₁, Q₃)

4.68 (3.53, 6.65)

4.54 (3.52, 6.41)

5.13 (3.54, 7.11)

Z = 1.663

Percentage of neutrophils, Mean ± SD

70.54 ± 11.65

69.96 ± 11.43

71.90 ± 12.03

t =  − 1.926

LYM, M (Q₁, Q₃)

1.29 (0.91, 1.80)

1.28 (0.93, 1.80)

1.31 (0.85, 1.79)

Z =  − 0.681

Percentage of lymphocytes, M (Q₁, Q₃)

19.42 (12.47, 27.13)

19.60 (12.80, 27.50)

18.90 (11.25, 26.30)

Z =  − 1.593

MONO, M (Q₁, Q₃)

0.44 (0.33, 0.60)

0.44 (0.34, 0.60)

0.44 (0.33, 0.61)

Z =  − 0.826

Percentage of monocytes, M (Q₁, Q₃)

6.30 (4.90, 8.00)

6.40 (5.00, 8.20)

6.10 (4.80, 7.80)

Z =  − 1.907

EOS, M (Q₁, Q₃)

0.10 (0.03, 0.19)

0.10 (0.03, 0.19)

0.08 (0.03, 0.16)

Z =  − 0.577

Percentage of eosinophils, M(Q₁, Q₃)

1.46 (0.40, 2.90)

1.50 (0.40, 3.00)

1.40 (0.40, 2.55)

Z =  − 0.830

RDW, Mean ± SD

13.20 ± 1.05

13.20 ± 1.04

13.20 ± 1.06

t = 0.053

ALT, M (Q₁, Q₃)

15.50 (11.00, 23.00)

15.40 (11.00, 23.00)

15.60 (10.00, 23.35)

Z =  − 0.244

AST, M (Q₁, Q₃)

18.00 (14.00, 23.10)

18.00 (14.30, 23.70)

17.30 (13.25, 22.20)

Z =  − 1.658

TBIL, M (Q₁, Q₃)

9.35 (6.70, 13.30)

9.60 (6.80, 13.40)

9.00 (6.60, 12.45)

Z =  − 0.492

ALB, Mean ± SD

39.89 ± 4.67

39.95 ± 4.78

39.74 ± 4.38

t = 0.521

BUN, M (Q₁, Q₃)

5.44 (4.45, 6.68)

5.47 (4.43, 6.77)

5.36 (4.51, 6.64)

Z =  − 0.221

Cr, M (Q₁, Q₃)

76.20 (64.40, 93.75)

75.80 (64.00, 92.50)

78.70 (65.20, 93.95)

Z = 1.035

Uric acid, M (Q₁, Q₃)

288.50 (226.00, 352.00)

289.00 (232.00, 355.00)

287.00 (215.50, 347.00)

Z =  − 0.829

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

8.40 (2.00, 36.67)

8.00 (2.20, 34.40)

9.30 (1.75, 43.15)

Z = 0.697

mMRC grade, n (%)

Z = 1.634

 0

1 (0.16)

0 (0.00)

1 (0.52)

 1

138 (21.70)

103 (23.15)

35 (18.32)

 2

279 (43.87)

196 (44.04)

83 (43.46)

 3

189 (29.72)

131 (29.44)

58 (30.37)

 4

29 (4.56)

15 (3.37)

14 (7.33)

CAT score, Mean ± SD

20.28 ± 5.34

20.16 ± 5.19

20.58 ± 5.67

t =  − 0.917

FEV₁, M (Q₁, Q₃)

1.60 (1.10, 2.21)

1.60 (1.09, 2.21)

1.64 (1.12, 2.20)

Z = 0.081

FVC, M (Q₁, Q₃)

2.26 (1.66, 3.64)

2.23 (1.65, 3.60)

2.30 (1.67, 3.67)

Z = 0.381

FEV1/FVC, Mean ± SD

67.25 ± 13.27

67.23 ± 13.17

67.30 ± 13.50

t =  − 0.060

FEV₁ in predicted value FEV₁, Mean ± SD

55.33 ± 17.82

55.81 ± 17.73

54.19 ± 17.97

t = 1.048

Use of systemic glucocorticoid, n (%)

χ² = 2.348

 No

472 (74.21)

338 (75.96)

134 (70.16)

 Yes

164 (25.79)

107 (24.04)

57 (29.84)

Antibacterial agents, n (%)

χ² = 1.642

 No

13 (2.04)

7 (1.57)

6 (3.14)

 Yes

623 (97.96)

438 (98.43)

185 (96.86)

Oxygen therapy, n (%)

χ² = 0.220

 No

126 (19.81)

86 (19.33)

40 (20.94)

 Yes

510 (80.19)

359 (80.67)

151 (79.06)

Mechanical ventilation, n (%)

χ² = 0.098

 No

628 (98.74)

439 (98.65)

189 (98.95)

 Noninvasive ventilation

8 (1.26)

6 (1.35)

2 (1.05)

Group, n (%)

χ² = 1.687

 Non-readmission group

449 (70.60)

321 (72.13)

128 (67.02)

 Readmission group

187 (29.40)

124 (27.87)

63 (32.98)