Background/Purpose: Radiography of the sacroiliac joints (SIJ) in spondyloarthritis (SpA) is a valuable diagnostic tool but is unreliable and unresponsive for assessment of treatment effects. There is an unmet need for imaging tools to assess the potential disease-modifying effects of therapeutic agents early in SpA when disease is still confined to the SIJ. There has been limited assessment of MRI-based scores for structural lesions in the SIJ, which indicate that scoring fat metaplasia may discriminate between therapies. But the significance of this for structural damage is unclear. The SPARCC MRI SIJ Structural Score (SSS) assesses a broader spectrum of structural lesions and its potential to discriminate between therapies requires evaluation.

Methods: The SSS method assesses fat metaplasia (FAT), erosion (ER), backfill (BF), and ankylosis (ANK) according to standardized and validated definitions (Morpho). It scores 5 consecutive coronal slices anteriorly through the cartilaginous portion of the joint from the transitional slice, defined as the first slice in the cartilaginous portion that has a visible portion of the ligamentous joint. Lesions are scored dichotomously (present/absent) in SIJ quadrants (fat, erosion) or halves (backfill, ankylosis) using a direct online data entry system based on schematics of the SIJ. Scoring ranges are: FAT (0-40), ER (0-40), BF (0-20), ANK (0-20). After a calibration exercise, two readers independently scored 147 pairs of scans conducted at baseline and 2 years from a prospective cohort of patients with SpA who received either standard (n=69) or anti-TNF (n=78) therapies. Baseline status and change scores were assessed by intraclass correlation coefficient (ICC3,1), and smallest detectable change (SDC) was calculated using ANOVA and expressed as an absolute value and as a percentage of the maximum score. Discrimination was assessed using Guyatt’s effect size and treatment group differences using the Mann-Whitney test.

Results:

Baseline clinical characteristics were similar except for significantly higher CRP and BASDAI in the anti-TNF treated group. Baseline SSS ANK and BF scores were also significantly higher in the anti-TNF treated group (p=0.014 and 0.022, respectively). The number (%) of patients with new and resolved erosions at 2 years was 6 (7.6%) and 32 (40.5%) in the anti-TNF group versus 16 (23.5%) and 21 (30.9%) in the standard group (χ²=7.4, p=0.02). Significantly greater increase in SSS Fat and decrease in SSS ER scores was evident in the anti-TNF treated group (Table).

	Baseline ICC [95%CI]	Change ICC [95%CI]	SDC (% maximum range)	Mean BL Score (SD)		Mean change score (SD)		Guyatt’s ES	P value
				Anti-TNF	Standard	Anti-TNF	Standard
FAT	0.72 [0.47-0.84]	0.40 [0.25-0.53]	3.4 (8.5%)	3.6 (5.1)	4.0(6.6)	0.7(2.2)	0.2(1.5)	0.46	0.017
BACKFILL	0.48 [0.24-0.64]	0.49 [0.35-0.61]	4.2 (21.2%)	3.7 (4.5)	2.2(3.1)	0.1(2.9)	0.4(1.9)	0.03	NS
EROSION	0.56 [0.30-0.72]	0.51 [0.38-0.62]	4.7 (11.7%)	2.7 (3.2)	3.6(4.4)	-1.5(2.8)	-0.5(2.7)	0.55	0.017
ANKYLOSIS	0.97 [0.96-0.98]	0.63 [0.52-0.72]	2.1 (10.6%)	7.3 (8.5)	4.1(7.0)	0.4 (1.6)	0.3 (1.2)	0.33	NS

Conclusion: The SPARCC SSS method for assessment of structural lesions has discriminative capacity in demonstrating significantly greater reduction in erosion in patients receiving anti-TNF.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/anti-tumor-necrosis-fator-therapy-is-associated-with-resolution-of-erosion-in-the-sacroiliac-joints-of-patients-with-spondyloarthritis/