Low-Dose CT Scans Detect Bone Proliferation in Ankylosing Spondylitis

Low-dose computed tomography detects more bone proliferation in patients with ankylosing spondylitis compared with conventional radiography.

Low-dose computed tomography (CT), which scans the entire vertebral column, detects more bone proliferation in patients with ankylosing spondylitis (AS) compared with conventional radiography (CR), which is limited to the cervical and lumbar spine, according to the results of a recent observational cohort study published in the Annals of the Rheumatic Diseases.

The objective of the study was to compare the CT Syndesmophyte Score for low-dose CT with the modified Stoke Ankylosing Spondylitis Spine Score for CR in patients with AS. Data from the Sensitive Imaging in Ankylosing Spondylitis (SIAS) cohort were used for this analysis. Patients with ankylosing spondylitis in the SIAS cohort had lateral cervical and lumbar spine CR and whole-spine low-dose CT at baseline and at 2 years. Two readers scored the CR and low-dose CT images, which were paired by patient, blinded to time order, per imaging modality used. The total score analysis used the average scores of readers per corner on CR or quadrant on the low-dose CT scan. The syndesmophyte analysis used individual reader and consensus scores with respect to new or growing syndesmophyte at the same corner or quadrant.

A total of 50 patients were included in the syndesmophyte analysis, and 37 were included in the total score analysis. The mean status scores for modified Stoke Ankylosing Spondylitis Spine Score and CT Syndesmophyte Score at baseline were 17.9±13.8 and 161.6±126.6, respectively; mean progression was 2.4±3.8 and 17.9±22.1. Overall, 3 times as many patients exhibited new or growing syndesmophytes at ≥3 quadrants on low-dose CT compared with ≥3 corners on CR for individual readers. In 50 patients, 36 new or growing syndesmophytes were detected on CR vs 151 on low-dose CT, with most detected in the thoracic spine.

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The investigators concluded that the greatest benefits of low-dose CT were its ability to analyze the thoracic spine and the opportunity to analyze the growth of syndesmophytes in greater detail. With the use of this scoring system, it is now feasible to use low-dose CT scans, with a relatively low radiation dose, in research, including medication trials.

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de Koning A, de Bruin F, van den Berg R, et al. Low-dose CT detects more progression of bone formation in comparison to conventional radiography in patients with ankylosing spondylitis: results from the SIAS cohort [published online November 10, 2017]. Ann Rheum Dis. doi:10.1136/annrheumdis-2017-211989