Table 2.

Summary of patients' ages at examination two and interval between examinations one and two for patients with no interval changes, minor CT changes within the same scoring grade, progression into sacroiliitis, and progression of already established sacroiliitis. Age and examination interval in years.

	No changes between examinations	New sacroiliitis	Progression of sacroiliitis	Minor changes	All patients
Number	282	9	34	9	334
Median patient age	38	39	34.5	32	38
Patient age range	19–72	29–58	21–66	27–45	19–72
Median interval between examinations	3	5	4	3	4
Range of interval between examinations	<1–21	1–21	<1–16	<1–17	<1–21