Page 30 - Recognizing axial spondyloarthritis - Janneke de Winter

CHAPTER TWO
axial SpA but did not lead to a higher use of highly effective targeted therapies such as TNF inhibition, suggesting that treatment was not completely tailored to disease activity. For the sake of clarity, it needs to be specified there are no major restrictions to access to TNF inhibition in the Netherlands and that other targeted therapies, such as IL-17 inhibition, were not available at the time of this cross- sectional cohort study.
A striking finding in this axial vs. peripheral SpA analysis was the fact that 21% of the patient with peripheral SpA had a history of back pain. The back pain can be explained by the fact that the criteria for axial SpA require present inflammatory back pain; therefore, a patient with peripheral SpA and a history of or non-inflammatory back pain will still be classified as peripheral SpA and it remains unknown if this back pain is related to SpA or to other, concomitant conditions such as degenerative disc disease. This question could be addressed by MRI imaging of the axial skeleton in these patients, an approach which was not systematically applied in the current study.
The main finding of the study, however, is that half of the patients with axial SpA have also signs of peripheral disease. Further analysis of ‘pure axial SpA’ versus combined axial and peripheral SpA revealed that, albeit both subgroups were very similar in terms of demographics, HLA-B27 positivity, family history, and presence of extra-articular manifestations, the combined SpA had significantly higher disease activity despite increased use of csDMARDs. Moreover, a comparison with peripheral SpA revealed that combined SpA patients used less csDMARDs despite higher disease activity (data not shown). Interestingly, we noted that the higher disease activity in combined SpA did not translate in higher use of TNF inhibition in this patient subset. Whereas cDMARDs are not effective for axial disease (24–26) and may have limited efficacy for peripheral disease (24,26–28), it is well established that TNF inhibition is effective for both axial and peripheral disease (29–38). In the setting of the current study, patients with combined axial and peripheral SpA are eligible for targeted therapies and access to TNF inhibition was not restricted. Collectively, these data therefore indicate that patients with combined axial and peripheral disease form an important subgroup of patients with axial SpA as defined by the ASAS criteria as they represent half of the axial SpA patients and have a higher disease burden. However, they do not appear to be treated ‘to target’ based on disease activity, suggesting that the additional disease burden related to concomitant peripheral disease is underestimated in axial SpA.
Whereas the design of this cross-sectional observational cohort study did not allow to formally test the potential benefit of treatment intensification in the subset of SpA patients with combined axial and peripheral disease, different approaches may be considered in follow-up studies to increase recognition and appropriate treatment of peripheral disease in patients classified as axial SpA. For example, several previous studies used the ASAS criteria differently than proposed - that is classifying patients with combined axial and peripheral disease exclusively according to the axial arm of the criteria- in order to better reflect
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