Background/Purpose: For assessing structural damage in AS on spinal X-rays the Bath Ankylosing Spondylitis Radiology Index (BASRI) and modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) scoring systems can be used. No comparison of the results of those 2 scores is available at an early stage of the disease. The purpose of this study is to present the prevalence of abnormalities based on the BASRI and mSASSS in patients with recent inflammatory back pain (IBP) and to compare these 2 scores.

Methods: Patients aged 18-50 with recent IBP (≥3 months, ≤3 years) from 25 participating centres in France were included in the DESIR (Devenir des Spondylarthropathies Indifferenciées Récentes)-cohort (n=708). All available baseline spinal X-rays (cervical and lumbar) were scored by 2 well-calibrated central readers independently, blinded for clinical data. When readers disagreed, an experienced radiologist served as adjudicator. BASRI and mSASSS were calculated from the mean of the scores of the 2 readers (and adjudicator if applicable).

Patients were classified according to the ASAS axial SpondyloArthritis (ASAS axSpA) criteria into patients fulfilling the imaging arm, either fulfilling or not fulfilling the modified New York (mNY) criteria, fulfilling the clinical arm and not fulfilling (no-axSpA patients) the criteria.

Results: Patients with complete X-ray data (n=637) were included in these analyses. Overall, 87.8% of the patients had no definite abnormalities assessed by mSASSS <2, and 88.5% by BASRI <2 (see table); those values were 88.5% and 89.0% within the ASAS axSpA patient group, respectively. A BASRI of ≥2 was scored more frequently in the imaging arm compared to the clinical arm of the ASAS criteria and the no-axSpA patient group (table). When comparing mSASSS and BASRI readings, using a cut-off of ≥2 (definite abnormalities) for both scoring methods, we found a very high percentage of agreement in all the different patient groups: range 95.4% to 98.2%.

Only in few patients syndesmophytes were found, and these were present in all patients groups (see table). More syndesmophytes were present in the cervical spine than in the lumbar spine. The number of syndesmophytes in the cervical vs the lumbar spine was 6 vs 3 in the no-axSpA group, 6 vs 1 in the clinical arm, 5 vs 1 in the imaging mNY-group, and  8 vs 1 in the imaging mNY+ group.

Conclusion: The agreement between mSASSS and BASRI ≥2 is very high in all patient groups. Abnormalities typical for AS such as syndesmophytes are generally infrequent in this early cohort, but if observed, syndesmophytes are more frequent in the cervical spine compared to the lumbar spine. An mSASSS and BASRI of ≥2 is more often seen in patients fulfilling the ASAS classification criteria compared to no-SpA patients. 

	ASAS axSpA, n=453			No-SpA, n=184
	Imaging arm		Clinical arm n=199
	mNY+ n=135	mNY- n=119
mSASSS <2	123 (91.9%)	100 (84.0%)	178 (89.4%)	158 (85.9%)
mSASSS ≥2 & <5	4 (3.0%)	8 (6.7%)	9 (4.5%)	7 (3.8%)
mSASSS ≥5 & <10	3 (2.2%)	2 (1.7%)	1 (0.5%)	0
mSASSS ≥10 & ≤15	1 (0.7%)	0	2 (1.0%)	3 (1.6%)
Total BASRI <2	117 (86.7%)	104 (87.4%)	182 (91.5%)	161 (87.5%)
Total BASRI = 2	10 (7.4%)	4 (3.4%)	7 (3.5%)	5 (2.7%)
Total BASRI = 3	2 (1.5%)	2 (1.7%)	0	1 (0.5%)
Total BASRI = 4	2 (1.5%)	0	1 (0.5%)	0
Total BASRI = 5	0	0	0	1 (0.5%)
No syndesmophytes	125 (92.6%)	105 (88.2%)	182 (91.5%)	161 (87.5%)
≥1 & <5 syndesmophytes	6 (4.4%)	3 (2.5%)	8 (4.0%)	5 (2.7%)
≥5 & <10 syndesmophytes	0	2 (1.7%)	0	2 (1.1%)
Missings	4 (3.0%)	9 (7.6%)	9 (4.5%)	16 (8.7%)

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comparison-of-the-performance-of-the-basri-and-msasss-in-patients-with-early-inflammatory-back-pain-from-the-desir-cohort/