Background/Purpose: Radiographic damage is one of the core outcomes in axial SpA and it is usually assessed with the modified Stoke Ankylosing Spondylitis (AS) Spine Score (mSASSS). The recently proposed Radiographic AS Spinal Score (RASSS)[1] includes an assessment of the lower thoracic vertebrae, under the hypothesis that most progression occurred in these segments. We aimed to compare the mSASSS and RASSS with regard to efficiency and added value.

Methods: Two-yearly spinal radiographs from patients followed in the Outcome in AS International Study (OASIS) were used. Two readers independently scored the x-rays, and averaged scores per vertebral corner (VC) were used. Only radiographs with ≤3 missing VCs per segment (cervical and lumbar, the latter with 4 thoracic VCs included as described for the RASSS) were included, so that both scores could be calculated. Status- and 2-year progression scores of both scoring methods were compared, first in terms of their availability. To assess the potential additional value of including the thoracic segment in the score, the relative contribution (in %) to the 2-year total RASSS progression of each spinal segment (cervical, thoracic and lumbar) was determined, and compared to the expected contribution, assuming a balanced segmental progression and proportional to the number of sites (12 cervical VCs, 4 thoracic VCs and 12 lumbar VCs).

Results: The mSASSS could be scored in a total of 809 radiographs. The RASSS could be calculated in 78% of these radiographs. In 58% of those, the RASSS was calculated based on 1 or 2 present thoracic VC scores (of the 4 possible thoracic VC scores), and the remaining 2-3 had to be imputed because they were missing (these imputed VCs were therefore uninformative). There were 520 two-year mSASSS interval progression scores available, and in 63% of them a 2-year RASSS interval progression score could be determined.  

Of all the radiographs in which both scores could be determined (n=629), the mean (SD) status- score was 15.5 (17.9) units for the mSASSS and 18.0 (20.9) units for the RASSS. The mean (SD) 2-year interval progression scores (in 330 two-year intervals) were 2.0 (3.6) for the mSASSS and 2.4 (4.4) for the RASSS. Exclusive progression of the thoracic segment occurred in only 5% of the cases. There were no significant differences between the observed and expected contributions of the thoracic segment to progression (Table), whilst progression was more frequently than expected observed in the cervical spine, and less frequently in the lumbar spine.

Conclusion: The determination of a RASSS for status or progression of radiographic abnormalities in the spine is frequently impossible or strongly influenced by non-contributory imputation. In comparison to the conventional mSASSS method, the contribution of thoracic VCs in the RASSS-method is negligible, and does not justify the additional scoring efforts.  

References:A&R:61,764-71

Table – Ratio of 2-year progression in each of the spinal segments of the RASSS
	Relative contribution to total RASSS progression (in %)
	Expected	Observed	P-value for the difference
Cervical segment (12 VCs)	43	55	0.09
Lumbar segment (12 VCs)	43	29	0.04
Thoracic segment (4 VCs)	14	16	0.70
Total (28 VCs)	100	100

---

« Back to 2012 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/scoring-radiographic-progression-in-axial-spa-should-we-use-the-modified-stoke-in-ankylosing-spondylitis-spine-score-or-the-radiographic-ankylosing-spondylitis-spinal-score/