Background The overall work disability in AS patients benefit from anti-TNF treatment.1 Patients with nr-axSpA have comparable clinical phenotypes and burden of disease, requiring treatment irrespective of the presence of radiographic damage.2 It could be hypothesized that the two conditions reflect different aspects of one disease progression.
Objectives To compare baseline characteristics and work disability before and after anti-TNF treatment start between patients with AS and nr-axSpA.
Methods Within the South Swedish Arthritis Treatment Group register we identified 103 AS and 75 nr-axSpA patients (the latter fulfilling the ASAS criteria for axial spondyloarthritis without radiographic sacroiliitis on plain x-ray) aged 17-62 years starting anti-TNF treatment 2004-2011. Patients were linked by personal identification numbers to Swedish social insurance agency registry data on work disability. Total work disability (sick leave plus disability pension), sick leave, and disability pension are presented one year before to two years after anti-TNF initiation (by quarters of a year). Population references are included to exclude potential secular trends in work disability.
Results Patients with nr-axSpA were younger (median 35 vs 40y p=0.014), had shorter disease duration (median 5.8 vs. 10.2y p=0.003), and less concomitant DMARDs (76 vs 47% p<0.001) at anti-TNF initiation. No statistically significant baseline differences were observed regarding sex (p=0.547) or VAS pain (p=0.907). The year before anti-TNF initiation the AS group displayed more work disability than the patients with nr-axSpA (mean 50.5 vs 37.4 days p<0.007), primarily due to a greater proportion of patients with AS having some level of disability pension (29 vs. 9%, p=0.001). After treatment start mean work disability decreased more for patients with nr-axSpA than AS, again mostly explained by a greater proportion within the AS group receiving disability pension, and hence less likely to decrease their work disability. Conversely, mean disability pension days increased more among AS patients after treatment initiation (p<0.001). The observed between-group differences after treatment start remained when adjusting for age, sex, and year of anti-TNF initiation.
Conclusions Patients with nr-axSpA had less disability pension, indicating less permanently reduced work disability, than their AS counterparts. Whether this is related to the hypothesis that nr-axSpA and AS represent different phases of a disease progression remains to be further explored.
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Rudwaleit M, Haibel H, Baraliakos X, et al. The early disease stage in axial spondylarthritis: results from the German Spondyloarthritis Inception Cohort. Arthritis Rheum 2009;60:717–27.
Disclosure of Interest A. Jöud Paid instructor for: Pfizer, T. Olofsson: None declared, L. Jacobsson Paid instructor for: Pfizer, UCB, and Abbvie, J. A. Karlsson: None declared, H. Bliddal Paid instructor for: Pfizer, UCB, Abbvie, Celgene, Bristol-Myers Squibb, and MSD, L. E. Kristensen Paid instructor for: Pfizer, UCB, Abbvie, Celgene, Bristol-Myers Squibb, and MSD