Table 4.

Comparison of radiographic measures for new bone formation in ankylosing spondylitis, or radiographic axial spondyloarthritis.^**

	mSASSS	CTSS	Quantitative Syndesmophyte height volume
Imaging modality	spine radiograph	low dose CT	full dose CT
Spine segments	cervical and lumbar spine	cervical, thoracic and lumbar spine	thoracic and lumbar spine
Number of scored intervertebral disk spaces (IDS)	12 (C2/C3 to C7/T1, T12/L1 to L5/S1)	23 (C2/C3 to L5/S1)	13 (T3/T4 to L3/L4)
Number of scoring sites per IDS	2	8	circumferential
Total score	0 – 72	0 – 552	not applicable
Training human readers	needed	needed	not needed
Sensitivity to change (in 2 years)	mSASSS increase in 30 – 40% patients	any net change in 61 –76% patients; the SDC in 37 – 43% patients	volume increase in more than 70% patients
Inter-reader ICC of change scores	0.17 – 0.67	whole spine: 0.77 spine segments: 0.32–0.75	Not applicable: measured by computer algorithm, no human readers involved.
Radiation	1.5mSV*	4 mSV	8 mSV

mSASSS: modified Stoke AS Spine Score; CTSS: computed tomography syndesmophyte score; CT: computed tomography; SDC: smallest detectable change; ICC: Intraclass correlation coefficient; mSV: millisievert.

^*2 views.

^**MRI scoring method is not included here because it does not measure new bone formation.