Table 2 Clinical and radiological characteristics of ERA patients

HLA-B27, n (%)

39 (95)

Family history in 1^st degree relative of HLA-B27 associated disease, n (%)

6 (15)

Disease onset in years, median (IQR)

11 (10–14)

Age of diagnosis in years, median (IQR)

12 (10.3–15)

Imaging modalities of SIJ, n (%)

40 (98)

 Radiograph, n (%)

36 (88)

 MRI, n (%)

29 (71)

 CT, n (%)

1 (2)

Sacroiliitis, n (%)

32 (78)

Duration from disease onset to sacroiliitis in months, median (IQR)

17 (4–62)

Sacroiliac joint structural changes, n (%)

30 (73)

Duration from disease onset to SIJ structural changes in months, median (IQR)

25 (14–64)

Duration from diagnosis of sacroiliitis to SIJ structural changes in months, median (IQR)

0 (0–12)

 Erosions, n (%)

22 (54)

 Sclerosis, n (%)

19 (46)

 Joint space narrowing, n (%)

7 (17)

 Ankylosis, n (%)

2 (5)

 Fatty change, n (%)

1 (2)