Table 2 Sensitivity analyses of the associations between childhood infections and a later diagnosis of ankylosing spondylitis

Including only cases matched at an age of 27 years or older

Cases (n = 1757)

Controls (n = 7305)

OR

95 % CI

 All infections^a

258 (14.7)

964 (13.2)

1.13

0.97–1.32

 Enteric^b

74 (4.2)

333 (4.6)

0.91

0.70–1.19

 Appendicitis

30 (1.7)

169 (2.3)

0.72

0.49–1.07

 Appendectomy

46 (2.6)

234 (3.2)

0.82

0.59–1.13

 Respiratory tract^c

159 (9.0)

529 (7.2)

1.27

1.05–1.54

 Tonsillitis

49 (2.8)

169 (2.3)

1.16

0.83–1.61

 Tonsillectomy^d

43 (2.4)

151 (2.1)

1.12

0.79–1.59

 Skin

15 (0.9)

66 (0.9)

0.93

0.53–1.64

 Urogenital tract

6 (0.3)

24 (0.3)

1.02

0.41–2.50

 Other

35 (2.0)

113 (1.5)

1.34

0.91–1.97

Including only cases treated with methotrexate, sulphasalazine, and/or TNFi

Cases (n = 794)

Controls (n = 3288)

OR

95 % CI

 All infections^a

141 (17.8)

553 (16.8)

1.06

0.86–1.31

 Enteric^b

40 (5.0)

185 (5.6)

0.87

0.61–1.25

 Appendicitis

12 (1.5)

85 (2.6)

0.58

0.31–1.06

 Appendectomy

20 (2.5)

116 (3.5)

0.71

0.44–1.16

 Respiratory tract^c

93 (11.7)

329 (10.0)

1.20

0.93–1.54

 Tonsillitis

34 (4.3)

96 (2.9)

1.48

0.98–2.24

 Tonsillectomy^d

27 (3.4)

78 (2.4)

1.42

0.90–2.24

 Skin

12 (1.5)

38 (1.2)

1.37

0.71–2.66

 Urogenital tract

1 (0.1)

16 (0.5)

0.28

0.037–2.10

 Other

14 (1.8)

59 (1.8)

0.991

0.54–1.81

Including only cases matched 2007–2011 and excluding all with immunosuppressive or cytostatic treatment, as well as specific treatment for inflammatory bowel disease, 1 year prior to match

Cases (n = 471)

Controls (n = 1836)

OR

95 % CI

 All infections^a

96 (20.4)

329 (17.9)

1.16

0.89–1.52

 Enteric^b

26 (5.5)

102 (5.6)

0.92

0.59–1.45

 Appendicitis

6 (1.3)

38 (2.1)

0.57

0.24–1.36

 Appendectomy

11 (2.3)

48 (2.6)

0.84

0.43–1.63

 Respiratory tract^c

63 (13.4)

191 (10.4)

1.33

0.97–1.81

 Tonsillitis

27 (5.7)

67 (3.6)

1.58

0.99–2.53

 Tonsillectomy^d

20 (4.2)

54 (2.9)

1.40

0.82–2.38

 Skin

3 (0.6)

21 (1.1)

0.56

0.16–1.90

 Urogenital tract

4 (0.8)

8 (0.4)

2.03

0.61–6.78

 Other

14 (3.0)

45 (2.5)

1.29

0.70–2.40

Prescription of antibiotics 1 year prior to match

131 (27.8)

478 (26.0)

Excluding inflammatory bowel disease^e

Cases (n = 2307)

Controls (n = 9584)

OR

95 % CI

 All infections^a

405 (17.6)

1555 (16.2)

1.10

0.97–1.25

 Enteric^b

108 (4.7)

528 (5.5)

0.84

0.67–1.04

 Appendicitis

35 (1.5)

244 (2.5)

0.59

0.41–0.84

 Appendectomy

56 (2.4)

312 (3.3)

0.74

0.55–0.98

 Respiratory tract^c

258 (11.2)

873 (9.1)

1.25

1.08–1.46

 Tonsillitis

87 (3.8)

257 (2.7)

1.37

1.07–1.77

 Tonsillectomy^d

78 (3.4)

219 (2.3)

1.42

1.09–1.85

 Skin

23 (1.0)

102 (1.1)

0.94

0.59–1.49

 Urogenital tract

9 (0.4)

40 (0.4)

0.90

0.44–1.86

 Other

53 (2.3)

192 (2.0)

1.18

0.87–1.62