Page 146 - Recognizing axial spondyloarthritis - Janneke de Winter

CHAPTER NINE
without peripheral disease manifestations and 117 (51%) had combined axial and peripheral disease. The group with combined axial and peripheral disease had the highest disease activity.
These results are of importance, since the treatment of axial disease in patients classified as ‘axial SpA’ by the ASAS criteria might prevail over the treatment of peripheral disease, while we showed that the latter contributes significantly to the disease activity. Clinical research programs on axial SpA should systemically include a careful evaluation of peripheral disease symptoms. Future research will have to show if indeed the current classification of patients with both axial and peripheral disease as axial SpA leads to worse treatment outcomes. In order to solve this issue, patients might be classified according to their prevailing symptom, as several recent studies pragmatically already did (1–5).
AS and non-radiographic axial SpA are phenotypically largely equal
In Chapter 3, we compared the prevalence of peripheral and extra-articular (uveitis, psoriasis, inflammatory bowel disease (IBD)) disease manifestations in the radiographic (ankylosing spondylitis, AS) and non-radiographic phenotype of axial SpA (nr-axial SpA) by performing a systematic literature search to identify publications describing the prevalence of peripheral and extra-articular disease manifestations in patients with AS and nr-axial SpA. We calculated the pooled prevalence and difference in prevalence.
Our study data show that peripheral and extra-articular disease manifestations are, with the exception of uveitis, frequent and equally prevalent in AS and nr- axial SpA. These data further support the concept of axial SpA being one disease continuum irrespective of the presence and extent of radiographic changes (6–8). Importantly, we should emphasize that phenotypic similarities do not logically imply that different forms of axial SpA are indeed identical, although family studies (9–15), studies after the immunopathologic basis of SpA (16–19), and clinical studies do provide evidence that justify handling them as one disease (20).
Recognizing the diagnosis of axial spondyloarthritis
To date, there are no biomarkers that yield sufficient specificity and sensitivity to identify axial SpA with a high level of certainty. The development of robust diagnostic biomarkers might shorten the current significant time to diagnosis of 5 to 11 years (21–24). Part II therefore focused on the identification and validation of promising biomarkers in the axial SpA field, predominantly those biomarkers suggested to serve a role in the diagnostic process.
There is no role for anti-CD74 antibodies in the diagnostic process of early axial SpA
Anti-CD74 IgG antibodies are reported to be elevated in axial SpA patients (25,26) In Chapter 4, we aimed to show the diagnostic value of anti-CD74 antibodies in axial SpA, particularly in early axial SpA. The results of Chapter 4 suggest that anti-CD74 antibodies have limited diagnostic value in patients with early back
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