# Table 1 Sensitivity analysis of the data before and after interpolation

Variable Before interpolation (n = 636) After interpolation (n = 636) Statistical magnitude P
Gender, n (%)    χ2 = 0.000 1.000
Male 425 (66.82) 425 (66.82)
Female 211 (33.18) 211 (33.18)
Age, mean ± SD 70.82 ± 9.88 70.82 ± 9.88 t = 0.000 1.000
Height, mean ± SD 1.67 ± 0.07 1.67 ± 0.07 t = 0.000 1.000
Weight, mean ± SD 65.50 ± 8.44 65.50 ± 8.44 t = 0.000 1.000
Acute exacerbation in previous 1 year, n (%)    χ2 = 0.000 1.000
No 430 (67.61) 430 (67.61)
Yes 206 (32.39) 206 (32.39)
Smoking status, n(%)    χ2 = 0.000 1.000
Never smoked 321 (50.47) 321 (50.47)
Smoked before 93 (14.62) 93 (14.62)
Smoker at present 222 (34.91) 222 (34.91)
Daily amount of smoking, M (Q1, Q3) 0.00 (0.00, 15.00) 0.00 (0.00, 15.00) Z = 0.000 1.000
Duration of smoking, M (Q1, Q3) 0.00 (0.00, 30.00) 0.00 (0.00, 30.00) Z = 0.000 1.000
LAMA, n (%)    χ2 = 0.000 1.000
No 479 (75.31) 479 (75.31)
Yes 157 (24.69) 157 (24.69)
SAMA, n (%)    χ2 = 0.000 1.000
No 634 (99.69) 634 (99.69)
Yes 2 (0.31) 2 (0.31)
LABA, n (%)    χ2 = 0.000 1.000
No 413 (64.94) 413 (64.94)
Yes 223 (35.06) 223 (35.06)
SABA, n (%)    χ2 = 0.000 1.000
No 555 (87.26) 555 (87.26)
Yes 81 (12.74) 81 (12.74)
PDE4I, n (%)    χ2 = 0.000 1.000
No 617 (97.01) 617 (97.01)
Yes 19 (2.99) 19 (2.99)
ICS, n (%)    χ2 = 0.000 1.000
No 422 (66.35) 422 (66.35)
Yes 214 (33.65) 214 (33.65)
Congestive heart-failure, n (%)    χ2 = 0.000 1.000
No 572 (89.94) 572 (89.94)
Yes 64 (10.06) 64 (10.06)
Diabetes, n (%)    χ2 = 0.000 1.000
No 498 (78.30) 498 (78.30)
Yes 138 (21.70) 138 (21.70)
Hypertension, n (%)    χ2 = 0.000 1.000
No 280 (44.03) 280 (44.03)
Yes 356 (55.97) 356 (55.97)
Atrial fibrillation, n (%)    χ2 = 0.000 1.000
No 596 (93.71) 596 (93.71)
Yes 40 (6.29) 40 (6.29)
Combined with other diseases, n (%)    χ2 = 0.000 1.000
No 432 (67.92) 432 (67.92)
Yes 204 (32.08) 204 (32.08)
Systolic blood pressure, Mean ± SD 133.46 ± 17.34 133.46 ± 17.34 t = 0.000 1.000
Diastolic blood pressure, Mean ± SD 78.73 ± 10.82 78.73 ± 10.82 t = 0.000 1.000
Respiratory rate, Mean ± SD 19.28 ± 2.53 19.28 ± 2.53 t = 0.000 1.000
Temperature, mean ± SD 36.86 ± 0.56 36.86 ± 0.56 t = 0.000 1.000
Heart rate, mean ± SD 81.65 ± 11.35 81.65 ± 11.35 t = 0.000 1.000
Hb, mean ± SD 132.50 ± 17.34 132.51 ± 17.26 t =  − 0.002 0.998
RBC, mean ± SD 4.33 ± 0.55 4.33 ± 0.55 t = 0.046 0.963
WBC, M (Q1, Q3) 6.89 (5.51, 8.97) 6.90 (5.53, 8.93) Z =  − 0.027 0.979
PLT, M (Q1, Q3) 188.00 (151.00, 235.75) 188.50 (151.75, 235.00) Z =  − 0.043 0.966
NEUT, M (Q1, Q3) 4.67 (3.52, 6.65) 4.68 (3.53, 6.65) Z =  − 0.044 0.965
Percentage of neutrophils, mean ± SD 70.51 ± 11.70 70.54 ± 11.65 t =  − 0.052 0.959
LYM, M (Q1, Q3) 1.28 (0.90, 1.80) 1.29 (0.91, 1.80) Z =  − 0.079 0.937
Percentage of lymphocytes, M (Q1, Q3) 19.40 (12.40, 27.30) 19.43 (12.47, 27.13) Z = 0.019 0.985
MONO, M (Q1, Q3) 0.44 (0.33, 0.60) 0.44 (0.33, 0.60) Z =  − 0.066 0.947
Percentage of monocytes, M (Q1, Q3) 6.30 (4.90, 8.10) 6.30 (4.90, 8.00) Z = 0.045 0.964
EOS, M (Q1, Q3) 0.10 (0.03, 0.19) 0.10 (0.03, 0.19) Z =  − 0.036 0.971
Percentage of eosinophils, M(Q1, Q3) 1.50 (0.40, 2.90) 1.46 (0.40, 2.90) Z = 0.018 0.986
RDW, mean ± SD 13.20 ± 1.07 13.20 ± 1.05 t =  − 0.020 0.984
ALT, M (Q1, Q3) 15.45 (10.93, 23.00) 15.50 (11.00, 23.00) Z =  − 0.027 0.978
AST, M (Q1, Q3) 18.00 (14.00, 23.17) 18.00 (14.00, 23.10) Z =  − 0.026 0.979
TBIL, M (Q1, Q3) 9.30 (6.65, 13.35) 9.35 (6.70, 13.30) Z =  − 0.013 0.989
ALB, mean ± SD 39.88 ± 4.68 39.89 ± 4.67 t =  − 0.035 0.972
BUN, M (Q1, Q3) 5.44 (4.44, 6.68) 5.44 (4.45, 6.68) Z =  − 0.014 0.989
Cr, M (Q1, Q3) 76.00 (64.10, 93.90) 76.20 (64.40, 93.75) Z =  − 0.037 0.971
Uric acid, M (Q1, Q3) 288.00 (226.00, 352.00) 288.50 (226.00, 352.00) Z =  − 0.009 0.993
Hypersensitive C-reactive protein, M (Q1, Q3) 8.30 (2.00, 38.00) 8.40 (2.00, 36.67) Z =  − 0.655 0.512
mMRC grade, n (%)    Z = 0.000 1.000
0 1 (0.16) 1 (0.16)
1 138 (21.70) 138 (21.70)
2 279 (43.87) 279 (43.87)
3 189 (29.72) 189 (29.72)
4 29 (4.56) 29 (4.56)
FEV1, M (Q1, Q3) 1.60 (1.10, 2.21) 1.60 (1.10, 2.21) Z = 0.000 1.000
FVC, M (Q1, Q3) 2.26 (1.66, 3.64) 2.26 (1.66, 3.64) Z = 0.000 1.000
FEV1/FVC, mean ± SD 67.25 ± 13.27 67.25 ± 13.27 t = 0.000 1.000
FEV1 in predicted value FEV1, mean ± SD 55.33 ± 17.82 55.33 ± 17.82 t = 0.000 1.000
Use of systemic glucocorticoid, n (%)    χ2 = 0.000 1.000
No 472 (74.21) 472 (74.21)
Yes 164 (25.79) 164 (25.79)
Antibacterial agents, n (%)    χ2 = 0.000 1.000
No 13 (2.04) 13 (2.04)
Yes 623 (97.96) 623 (97.96)
Oxygen therapy, n (%)    χ2 = 0.000 1.000
No 126 (19.81) 126 (19.81)
Yes 510 (80.19) 510 (80.19)
Mechanical ventilation, n (%)    χ2 = 0.000 1.000
No 628 (98.74) 628 (98.74)
Noninvasive ventilation 8 (1.26) 8 (1.26)
Group, n (%)    χ2 = 0.000 1.000
Non-readmission group 449 (70.60) 449 (70.60)
Readmission group 187 (29.40) 187 (29.40)
BMI, mean ± SD 23.48 ± 2.95 23.48 ± 2.95 t = 0.000 1.000
CAT score, mean ± SD 20.28 ± 5.34 20.28 ± 5.34 t = 0.000 1.000
1. LAMA long-acting muscarinic antagonist, LABA long-acting β agonist, SAMA short-acting muscarinic antagonist, SABA short-acting β agonist, PDE4I phosphodiesterase 4 inhibitor, ICS inhaled corticosteroids, Hb hemoglobin, RBC red blood cells, WBC white blood cells, PLT platelets, NEUT neutrophil count, LYM lymphocyte count, MONO monocytes count, EOS eosinophil count, RDW red blood cell distribution width, ALT glutamic-pyruvic transaminase, AST glutamic oxalacetic transaminase, TBIL total bilirubin, ALB albumin, BUN blood urea nitrogen, Cr creatinine, mMRC modified Medical Research Council, CAT COPD assessment test, FEV1 forced expiratory volume in 1 s, FVC forced vital capacity