Different Types of Axial Spondyloarthritis Share the Same Other Diseases, Study Says

People with non-radiographic axial spondyloarthritis share the same disease comorbidities as those affected by ankylosing spondylitis, which may hold implications regarding treatment management, a study finds.

The findings, “Comparison of comorbidities and treatment between ankylosing spondylitis and non-radiographic axial spondyloarthritis in the United States,” were published in Rheumatology.

Axial spondyloarthritis (axSpA) is a type of arthritis that mainly affects the joints of the spine, causing chronic pain and lifelong physical disability. The disease can be divided into ankylosing spondylitis (AS), when joint damage is visible through imaging techniques called radiographs, or non-radiographic axial spondyloarthritis (nr-axSpA), when joint damage is not visible on plain-film radiographs.

AS and nr-axSpA share many clinical features, including disease burden, symptoms, and response to certain types of medications, including tumor necrosis factor (TNF) inhibitors. Treatment with these inhibitors block the activity of TNF, a signaling molecule involved in immune and inflammatory responses that is produced in excessive amounts in AS patients.

No biologic disease-modifying anti-rheumatic drugs (bDMARDS) targeting TNF are currently licensed in the U.S. for people with nr-axSpA. However, it recently has been reported that the use of bDMARDS by patients with AS and nr-axSpA is identical.

“Prescription of some bDMARDs may be directly influenced by the presence of certain comorbidities (e.g. cancer) and indirectly through inability to use NSAIDs (e.g. renal disease). Whether comorbidities are associated with bDMARD prescribing has not been examined,” the investigators said. NSAIDs are nonsteroidal anti-inflammatory drugs, such as ibuprofen.

In this study, researchers from the University of Liverpool, in collaboration with investigators from Harvard Medical School set out to compare the type and incidence of comorbidities, as well as bDMARDS use, in a large group of AS and nr-axSpA patients living in the U.S.

The cross-sectional study, based on information from electronic medical records stored at two academic hospitals in the U.S., identified 965 eligible patients.

A total 775 (80%) were considered to have axSpA; the remaining 190 (20%) were excluded. Among the 775 axSpA patients included in the study, 641 (83%) were classified as having AS and 137 (17%) as having nr-axSpA, based on radiographic information.

Demographic and clinical data showed the people with AS tended to be older (mean of 54 years versus 46), were mostly male (77% versus 64%), and had higher levels of inflammatory markers in their serum (median C-reactive protein levels of 3.4 versus 2.2 mg/dl), compared with the nr-axSpA patients.

Half of the 775 patients enrolled in the study were affected by at least one comorbidity, or other simultaneous disease. No differences were found in the average number of comorbidities between those with AS (1.5) and the nr-axSpA patients (1.3).

The most common comorbidities observed in both groups included anxiety (11%), heart disease (11%), cancer (11%), high blood pressure (9%), depression (8%), and diabetes (7%).

Similarly, no differences were found between the two groups regarding the percentage of patients using bDMARDS (55% of AS versus 52% of nr-axSpA patients). The most commonly used bDMARDS were adalimumab (31%, sold under the trade name Humira among others) and etanercept (29%, sold under the brand name Enbrel).

“Despite their younger age, nr-axSpA patients had similar comorbidity burdens as those with AS. We also found that AS and nr-axSpA patients received comparable treatment using bDMARDs, and that bDMARD use was not associated with comorbidities,” the researchers said.

“These findings highlight the importance of identifying and managing comorbidities in these patients and support a unified management approach for the full spectrum of axSpA,” they concluded.