Prevalence of axial spondyloarthritis in Poland.

The prevalence of axial spondyloarthritis (axSpA) in the published data varies significantly. Two types of axSpA can be distinguished depending upon the presence of abnormalities consistent with sacroiliitis on plain radiography: ankylosing spondylitis (AS) and nonradiographic axial SpA (nr-axSpA). The aim of this study is to perform a retrospective analysis of axSpA prevalence in Poland in the years 2008-2017. The National Health Fund (NHF) database for the period 2008-2017 was analysed. Data of all patients with the ICD-10 codes M46 (M46.1, M46.8, M46.9) or M45 (further named other inflammatory spondylopathies-OIS and AS, respectively) as the main or co-existing diagnosis were extracted and analysed. The AS prevalence was stable during the period under examination amounting to approximately 0.083%, while the OIS prevalence increased from 0.036 to 0.059%. For both men and women, the AS prevalence increased with age, reaching a maximum around the age of 70; however, in men, a marked increase in prevalence was observed earlier as compared to women (20-24 vs. 40-44 years, respectively). The OIS prevalence also increased with age; however, the maximum was reached earlier as in case of AS. Moreover, a sharp increase in OIS prevalence occurred earlier than in AS (15-19 years) with no difference between sexes. In Poland, approximately 0.1% of the population suffers from AS-the prevalence remained stable over the last decade. The prevalence of OIS increased markedly over the studied period which presumably reflects an increasing prevalence of nr-axSpA as the effect of the introduction of ASAS classification criteria for axSpA.