Low-dose CT Can Improve Assessment of Ankylosing Spondylitis Progression, Study Suggests

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by Alice Melao |

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Low-radiation dose computed tomography (ldCT) scans are more sensitive in detecting the progression of ankylosing spondylitis (AS) than commonly used radiographs, a study suggests.

Published in the journal Annals of the Rheumatic Diseases, the study showed that ldCTs combined with a specific scoring measure can provide more detailed and accurate information over more structures of the vertebral column, which can improve the diagnosis and assessment of patients with AS.

Ankylosing spondylitis is a progressive disease characterized by structural damage to the spine. It is common for patients to develop new bone formations in the spine that will affect mobility, and consequently lead to functional disability.

Currently, spinal damage is determined based on conventional radiographs and evaluation using the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). This score combines information on new bone formation with data on spinal deformation, such as erosions, sclerosis, and squaring, to provide a measure of disease progression.

Advances in radiograph imaging technologies have made possible the use of ldCT scans to evaluate the entire vertebral column. This new method has the potential to provide additional imaging data of the spine structures compared to conventional radiographs.

To facilitate the assessment of ankylosing spondylitis based on low-dose CT images, a new score was created — the CT Syndesmophyte Score (CTSS) — which provides a measure of bone proliferation.

In the study, “Low-dose CT detects more progression of bone formation in comparison to conventional radiography in patients with ankylosing spondylitis: results from the SIAS cohort,” a team led by researchers at Leiden University Medical Center in the Netherlands compared the accuracy of mSASSS and CTSS to assess ankylosing spondylitis progression.

The team collected data from 51 patients with AS who had previously participated in the Sensitive Imaging in Ankylosing Spondylitis (SIAS) study. All patients had been evaluated via conventional radiographs and ldCTs, both at the beginning of the study and after two years.

Researchers found that low-dose CTs could detect more bone proliferation than conventional radiographs, particularly in the region of the thoracic spine. Indeed, ldCTs were found to detect almost five times more new or growing spinal bones compared to radiographs.

Although the scales of the mSASSS and CTSS scoring methods are different, the researchers found that progression scores were higher for CTSS. In addition, comparison of any net change revealed that 84% of patients showed positive change on ldCTs vs. 46% in conventional radiographs.

Overall, these results show that low-dose CT can identify more bone growth in patients with ankylosing spondylitis, with a greater potential for detecting disease progression.

“The biggest advantages of ldCT were the ability to analyze the thoracic spine and the opportunity to analyze growth of syndesmophytes [spinal bone growth] in more detail,” the researchers wrote.

The team believes the CTSS method can allow the use of low-dose CTs to accurately assess disease progression in the clinic and research settings.

However, the use of ldCTs also has some disadvantages, such as the total radiation exposure. Although in low-dose CT the radiation dose is approximately 10 times lower than in regular CTs, it is still 10 times higher than that used in common radiographs.

Nonetheless, the team believes that “with further technical advances, it may be expected that additional reduction in dosing will become possible.”