Page 52 - Recognizing axial spondyloarthritis - Janneke de Winter

CHAPTER THREE
developed search strategy and other methods to increase finding accuracy (such as citation pearl growing). Within-study selection bias might be caused by different approaches of including patients: early spondyloarthritis-cohorts (such as DESIR, SPACE) possibly select different patients with shorter disease duration than do large observational SpA cohorts.
Furthermore, by applying the ASAS criteria for axial SpA, the prevalence of disease manifestations and characteristics might be artificially raised in nr-axSpA, because they are part of those classification criteria. The higher prevalence of uveitis in AS patients, however, does not support this hypothesis. On the other hand, the longer mean duration of symptoms in AS patients when compared to nr-axSpA in 5 of the 8 included studies might confound the interpretation of the ‘ever’ present results, this gives AS patients more time to accumulate disease manifestations, and might increase the prevalence of the ‘ever’ present manifestations. However, when we left out the studies with substantial differences in symptom duration, the results remained unchanged, except for uveitis, whose difference disappeared (data not shown).
Conclusions
This meta-analysis summarized the prevalence of peripheral or extra-articular disease in patients with AS and nr-axSpA. Awareness of the prevalent nature of these disease manifestations is important in the diagnostic process, both for treatment choices and for health-related quality of life. This meta-analysis provides evidence for the largely equal nature of disease manifestations in nr-axSpA and AS, which should have consequences for research and treatment strategies.
Acknowledgements: We acknowledge Sanne Jansen of Lorkeers, MD PhD at the University Medical Center Utrecht, for her assistance with the study design of the meta-analysis. We acknowledge René Spijker, information retrieval specialist at the Academic Medical Center/University of Amsterdam for assistance with the development of the search strategy. We acknowledge Zineb Ez-Zaitouni, PhD student at the Leiden University Medical Center, for collecting the data of the SPACE cohort. We acknowledge Maxime Dougados and Anna Moltó (DESIR), Martin Rudwaleit (GESPIC), Adrian Ciurea (SCQM), Eva Tomero (Esperanza), Salih Ozgocmen (ESPAC) and Uta Kiltz (Kiltz et al) for providing additional data. DB was supported by a VICI grant from The Netherlands Organization for Scientific Research (NWO), by an ERC grant and by a grant from the Dutch Arthritis Foundation (Reumafonds).
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