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17-06-2017 | Rheumatology | News | Article

EULAR 2017

Spondyloarthritis subtypes share comorbidities

medwireNews: Spondyloarthritis (SpA)-related comorbidities are associated with ankylosing spondylitis (AS), undifferentiated spondyloarthritis (uSpA), and psoriatic arthritis (PsA) subtypes of the disease, show study findings.

This suggests a substantial shared etiology among these rheumatic diseases, said presenting researcher Karin Bengtsson, from the University of Gothenburg in Sweden.

However, the strengths of these associations with SpA-related comorbidities differed, she added, being strongest for AS, closely followed by uSpA, whereas only a weak association was found among patients with PsA.

“And these differences in strengths point also toward a diverse etiology and especially for patients given a diagnosis of PsA in comparison to AS and uSpA.” Bengtsson explained.

The comorbidities studied were anterior uveitis, inflammatory bowel disease (IBD), psoriasis, and the cardiac manifestations aortic regurgitation and atrioventricular (AV) block I–III.

A total of 3884 AS patients, 8706 PsA patients, and 2655 uSpA patients were identified between 2001 and 2005 from the Swedish National Patient Register and comorbidities up to 2006 were assessed. Diagnoses were made according to registered ICD-10 criteria and patients who had more than one of the SpA subtypes were not included.

Each patient was matched for gender, year of birth, and county or residence with controls from the Swedish Total Population Register.

There were more men than women among the patients and the mean age was highest for patients with PsA (53.9 years) and lowest for those with uSpA (46.1 years). The PsA group had the highest percentage of patients taking disease-modifying anti-rheumatic drugs (DMARDs), primarily methotrexate, at 37.1%, compared with 21.8% of AS patients, but otherwise the proportions of patients taking non-steroidal anti-inflammatory drugs (NSAIDs) and corticosteroids were comparable, at 40 to 50% and 10%, respectively.

Anterior uvetis was the most common comorbidity, occurring in 21% of AS patients and 13% of those with uSpA. This was followed by IBD, which occurred in 9% and 5% of patients, respectively. Among PsA patients, each of these comorbidities occurred in approximately 2% of patients. Psoriasis occurred in 2% of patients with AS and 3% of those with uSpA, and as expected was close to 100% for patients with PsA.

“According to the registered ICD-10 codes, the cardiac manifestations occurred infrequently in all of the [SpA] subtypes, but they were still more infrequent in the matched controls. And the highest occurrence was noted in the patients with AS,” Bengtsson told delegates at the Annual European Rheumatology Congress (EULAR) 2017 in Madrid, Spain. 

The findings were more or less similar when the patients were stratified by sex, with only anterior uvetis occurring more frequently in male patients with uSpA than female patients, at 17% and 10%, respectively. And for the cardiac manifestations, the main finding was that they occurred particularly in male patients with AS.

Prevalence ratios for the comorbidities, most notably anterior uvetis, were significantly elevated in all the SpAsubtypes compared with the matched controls.

“Overall, the prevalence ratios were especially elevated in patients with AS, intermediately elevated in uSpA, whereas only slightly to moderately elevated in PsA,” said Bengtsson.

She concluded: “More or less as expected all the studied SpA-related comorbidities were associated with a diagnosis of AS, PsA and uSpA, and these results are compatible with a shared etiology between these [SpA] subtypes, which seems particularly substantial for patients given a diagnosis of AS or uSpA.”

By Lucy Piper

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