Comparison of comorbidities and treatment between ankylosing spondylitis and non-radiographic axial spondyloarthritis in the United States.

Objectives: This study aimed to compare comorbidities and biologic DMARD (bDMARD) use between AS and non-radiographic axial SpA (nr-axSpA) patients, using a large cohort of patients from routine clinical practice in the United States.
Methods: We performed a cross-sectional study using electronic medical records from two academic hospitals in the United States. Data were extracted using automated searches (⩾3 ICD codes combined with text searches) and supplemented with manual chart review. Patients were categorized into AS or nr-axSpA according to classification criteria. Disease features, comorbidities (from a list of 39 chronic conditions) and history of bDMARD prescription were compared using descriptive statistics.
Results: Among 965 patients identified, 775 (80%) were classified as having axSpA. The cohort was predominantly male (74%) with a mean age of 52.5 years (s.d. 16.8). AS patients were significantly older (54 vs 46 years), more frequently male (77% vs 64%) and had higher serum inflammatory markers than those with nr-axSpA (median CRP 3.4 vs 2.2 mg/dl). Half of all patients had at least one comorbidity. The mean number of comorbidities was 1.5 (s.d. 2.2) and similar between AS and nr-axSpA groups. A history of bDMARD-use was seen in 55% of patients with no difference between groups. The most commonly prescribed bDMARDs were adalimumab (31%) and etanercept (29%). Ever-prescriptions of individual bDMARDs were similar between AS and nr-axSpA.
Conclusion: Despite age differences, nr-axSpA patients had similar comorbidity burdens as those with AS. Both groups received comparable bDMARD treatment in this United States clinic-based cohort.
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