Background/Purpose:   With increasing focus on effective treatment intervention in early spondyloarthritis, there is an unmet need for reliable assessment of structural progression in the sacroiliac joints (SIJ) but radiography is unreliable for detecting change and lacks responsiveness. There has been limited validation of MRI-based scores for structural lesions in the SIJ, primarily based on cross-sectional data and recording fat metaplasia, but it is unclear whether change in structural progression can be reliably detected and change in which specific MRI lesions is most consistently detected over time.

Methods:   The SPARCC SIJ Structural Score (SSS) method for assessment of structural lesions on T1WSE MRI scans is based on: 1. Standardized and validated definitions (MORPHO) for fat metaplasia, erosion, backfill, and ankylosis, 2. Anatomical matching of all time points according to the transitional semi-coronal SIJ slice, defined as the first slice in the cartilaginous portion that has a visible portion of the ligamentous joint when viewed from anterior to posterior, 3. Dichotomous scoring (present/absent) of lesions in SIJ quadrants (fat, erosion) or halves (backfill, ankylosis) using a direct online data entry system based on schematics of the SIJ, 4. Assessment of 5 consecutive slices from the transitional slice anteriorly through the cartilaginous portion of the joint. Scoring ranges are: fat metaplasia (0-40), erosion (0-40), backfill (0-20), ankylosis (0-20). Four readers independently assessed 20 pairs of MRI scans from 20 cases (baseline, 2 years) blinded to time point (exercise 1). In exercise 2, 15 pairs of scans from exercise 1 were randomly scored with an additional 30 new pairs of scans from 30 cases (baseline, 2 years) to assess consistency of change in reliability data. This nested study design addresses the limitation for assessment of reliability posed by differences in progression rates between different study samples since changes in progression are typically small. Inter-observer reliability was assessed by intra-class correlation coefficient (ICC3,1).

Results:   Mean (SD) for baseline scores were 3.4(4.0), 3.1(3.4), 3.7(4.3), and 5.3(7.9) for fat, erosion, backfill and ankylosis, respectively. Corresponding mean (SD) change scores were 0.2 (1.4), -1.3 (2.1), 0.5 (2.5), and 0.1(1.1). Consistently very good reliability was observed for detection of 2-year progression in ankylosis. Consistently good reliability was also evident for detection of change in backfill. Reliability was least consistent for detection of change in erosion.

 

Table. ICC [95% CI] values

		Fat  metaplasia		Erosion		Backfill		Ankylosis
	Readers	Status	Change	Status	Change	Status	Change	Status	Change
Exercise 1 (n = 20)	All	0.72 [0.54-0.86]	0.68 [0.49-0.84]	0.60 [0.39-0.79]	0.59 [0.38-0.78]	0.86 [0.74-0.93]	0.55 [0.34-0.76]	0.98 [0.96-0.99]	0.79 [0.65-0.90]
	N = 15*	0.71 [0.49-0.87]	0.59 [0.34-0.81]	0.67 [0.43-0.85]	0.61 [0.37-0.82]	0.90 [0.79-0.86]	0.72 [0.51-0.88]	0.98 [0.95-0.99]	0.84 [0.70-0.94]
Exercise 2 (n = 45)	All	0.78 [0.69-0.86]	0.44 [0.29-0.60]	0.62 [0.49-0.75]	0.39 [0.24-0.56]	0.66 [0.53-0.77]	0.56 [0.41-0.69]	0.98 [0.97-0.99]	0.64 [0.51-0.76]
	N = 15*	0.80 [0.62-0.92]	0.42 [0.16-0.70]	0.53 [0.28-0.78]	0.32 [0.07-0.63]	0.76 [0.57-0.90]	0.58 [0.33-0.80]	0.97 [0.94-0.99]	0.84 [0.70-0.94]

* Cases read in both exercises

Conclusion: The SPARCC MRI SSS method is a reliable scoring method for detecting structural progression, especially ankylosis, even though progression is small.

---

« Back to 2013 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-spondyloarthritis-research-consortium-of-canada-mri-sacroiliac-joint-structural-score-a-method-for-reliable-detection-of-structural-progression/