Table 1 Baseline characteristics of participants in the modeling and validation groups.

n = 1241

n = 868

n = 373

Sex

 Male

639

446

193

0.986

 Female

602

422

180

Age

40.18 ± 14.97

40.57 ± 15.07

39.27 ± 14.74

0.156

Clinical features

 Duration from onset to admission (hour)

32.76 ± 124.73

34.025 ± 147.98

29.80 ± 28.43

0.420

 Right lower abdominal shift pain

824 (66.40%)

568 (65.43%)

256 (68.63%)

0.223

 Nausea

680 (54.79%)

469 (54.03%)

211 (56.56%)

0.447

 Vomiting

470 (37.87%)

333 (38.36%)

137 (36.72%)

0.631

 Diarrhea

70 (5.64%)

55 (6.34%)

15 (4.02%)

0.137

 History of appendicitis (month)

1.13 ± 0.34

1.12 ± 0.33

1.15 ± 0.36

0.238

 Preoperative temperature ℃

37.16 ± 0.80

37.18 ± 0.81

37.11 ± 0.19

0.146

 Peritonitis

849 (68.41%)

599 (69.01%)

250 (67.02%)

0.532

Laboratory parameters

 Preoperative CRP mg/L

37.73 ± 55.98

39.52 ± 57.84

33.58 ± 51.22

0.072

 Preoperative WBC 10⁹/L

13.66 ± 3.94

13.73 ± 4.03

13.50 ± 3.74

0.332

 Preoperative Lymphocyte

1.49 ± 0.81

1.50 ± 0.83

1.48 ± 0.78

0.833

 Preoperative Neutrophil

11.50 ± 4.35

11.60 ± 4.52

11.30 ± 3.93

0.282

 Preoperative L%

11.96 ± 7.67

11.89 ± 7.60

12.12 ± 7.83

0.635

 Preoperative N%

82.57 ± 8.88

82.62 ± 8.60

82.45 ± 9.49

0.769

 NLR

10.90 ± 10.95

10.95 ± 11.64

10.80 ± 9.14

0.805

Radiography feature

 Appendicolith

487 (39.24%)

343 (39.51%)

144 (38.60%)

0.812

 APE

426 (34.32%)

304 (35.02%)

122 (32.71%)

0.47

 Periappendiceal fat stranding

687 (55.35%)

471 (54.26%)

216 (57.91%)

0.261

 Appendix diameter (mm)

11.23 ± 3.28

11.3 ± 3.30

11.08 ± 3.26

0.265

 Complex appendicitis

356(27.88%)

248(28.57)

98(26.27%)

0.448