The incidence of spondyloarthritis in Slovenia

Epidemiological studies of spondyloarthritides (SpA) are rare and data for our country are lacking. We aimed to determine the incidence of SpA in a well-defined region in Slovenia. We performed a retrospective chart review of adults diagnosed with SpA between January 2014 and December 2016 at an integrated secondary/tertiary medical center, which provides rheumatology services to almost a half of the adult national population, that is, 700,000 adults. Potential cases were ascertained by searching the electronic medical records for ICD-10 codes M02(∗), M07(∗), M13(∗), M45(∗), M 46.1, K50(∗), K51(∗), and L40(∗). SpA cases were stratified as axial and peripheral SpA and then the annual incidence rates of SpA overall and both subsets were estimated. During the 3-year period we identified 302 SpA cases (55.0% males, median [interquartile range] age 46.7 [35.0–57.5] years). 98 (32.5%) of them had predominantly axial SpA and the remainder peripheral SpA. The estimated annual incidence rate per 100,000 adults in our region was 14.3 (95% confidence interval [CI] 12.8–16.0) for SpA overall, 4.6 (95% CI 3.8–5.6) for axial SpA, and 9.6 (95% CI 8.4–11.1) for peripheral SpA. The estimated annual incidence rate of 14.3 cases per 100,000 adults in SpA overall was comparable to that of rheumatoid arthritis in our population. The peripheral SpA was twice as common as axial SpA.