Prevalence of Sjögren's syndrome in the general adult population in Spain: estimating the proportion of undiagnosed cases

Abstract

To estimate the prevalence of Sjögren's syndrome (SS) in the adult Spanish population we performed a population-based multicenter cross-sectional study. Cases were defined by the American-European Consensus Group criteria proposed in 2002. A total of 4,916 subjects aged 20 years or over were included. The estimated prevalence of SS (including primary and secondary forms) in the adult population in Spain was 0.33% (95% CI 0.21-0.53). Extrapolating to the total population of the country aged ≥ 20 years (around 37.7 million persons), there would be around 125,000 cases of SS in Spain. Considering only primary SS, the estimated prevalence was 0.25% (95% CI 0.15-0.43) or 1 person in 400. The prevalence of primary SS in Spain is comparable to that reported in other European studies with a similar design and diagnostic criteria. Based on these results, primary SS could not be considered a rare (orphan) disease. Only 50% of cases had already been diagnosed with SS prior EPISER 2016 study, confirming the existence of a non-negligible proportion of undiagnosed cases in the general population.

Figure 1

Flowchart showing participants in the study. ^a27,892 refused in the very beginning of the phone call. ^bMainly after removal of duplicated interviews or excess numbers in certain sample strata. ^cNone of the 70 missing subjects had reported a previous diagnosis of SS or Sicca syndrome. ^dOnly 50% (10/20) of these cases had already been diagnosed with SS prior to the EPISER2016 study.

Figure 2

Flowchart showing article identification, inclusion and exclusion.