Prevalence of gout in the adult general population in Spain: Estimating the proportion of undiagnosed cases

Abstract Objective To estimate the prevalence of gout in Spain. Methods Cross-sectional, population-based study of people aged 20 years or older. First, randomly selected individuals were contacted by telephone and rheumatic disease screening questionnaires were conducted. If the first screening was positive, medical records were then reviewed and/or a phone questionnaire was conducted by a rheumatologist, followed by an appointment if necessary. Newly diagnosed cases had to fulfil the ACR/EULAR 2015 criteria. To calculate the prevalence and its 95% CI, the sample design was taken into account and weighing was calculated according to age, sex and geographic origin. Results In all, 4916 individuals were included, 1361 had a positive screening result for gout (59 of them reported a prior diagnosis). Of these, 51 were classified as missing and 95 were classified as gout cases. An additional case was detected through a positive screening for fibromyalgia and Sjogren's syndrome, although a previous gout diagnosis was confirmed by a review of the medical records. Of the 96 gout cases, 31 (32%) were de novo diagnoses. The estimated weighted prevalence of gout was 2.4% (95% CI 1.95–2.95), with a higher prevalence in men (4.55% [95%CI 3.65–5.65]) than women (0.38% [95%CI 0.19–0.76]). Conclusion EPISER2016 is the first population-based study to estimate the prevalence of gout in Spain. Undiagnosed patients accounted for a substantial proportion of cases, highlighting the need for population-approaches when estimating the prevalence of infra-diagnosed diseases. Reliable national approaches are key to obtaining accurate estimates of diseases to better aid healthcare and workforce planning.