What amount of structural damage defines sacroiliitis: a CT study

Area of Science:

• Radiology
• Rheumatology
• Medical Imaging

Background:

• Axial spondyloarthritis (axSpA) is a chronic inflammatory disease affecting the sacroiliac (SI) joints.
• Accurate imaging definitions are crucial for diagnosing axSpA, particularly using computed tomography (CT).

Purpose of the Study:

• To establish a data-driven definition for structural SI joint changes in axSpA using CT imaging.
• To evaluate the diagnostic performance of various imaging findings in axSpA.

Main Methods:

• A large cohort of 546 individuals, including axSpA patients, non-axSpA low back pain patients, and controls, underwent SI joint CT scans.
• Erosions, sclerosis, and ankylosis were assessed using a structured scoring system, with clinical diagnosis as the reference standard.

Main Results:

• Ankylosis and/or erosions in the middle and dorsal SI joint portions demonstrated high diagnostic performance (Sensitivity 67.6%, Specificity 96.3%).
• Including ventral erosions or sclerosis reduced overall diagnostic performance.

Conclusions:

• Ankylosis and/or erosions in the middle and dorsal SI joint portions are reliable CT markers for axSpA.
• Sclerosis and ventral erosions have lower specificity for axSpA in SI joint CT imaging.