The Cretan Lupus Registry “Leto”: incidence and prevalence over a 15-year period, clinical features and environmental factors in a homogeneous, south European population Gergianaki I.1,2, Repa A.1, Tzanakakis M.1, Fanouriakis A1, Adamichou C1., Pompieri A1., Spyrou G. 1, Kabouraki E.1, Mamoulaki M.3, Tzanakis I.4, Chatzi L.5, Sidiropoulos P.1,2, Boumpas D.2,6, Bertsias G.1,2 1Rheumatology, Clinical Immunology and Allergy, University of Crete, Heraklion, Greece; 2Institute of Molecular Biology-Biotechnology, FORTH, Greece; 3Rheumatologist, 4Department of Nephrology, Chania General Hospital, 5Department of Social Medicine, University of Crete, Greece,6University of Athens, Athens, Greece Introduction Epidemiological description of SLE occurrence at the population level is challenging due to the rarity and multisystem nature of the disease that maybe is diagnosed and managed at different levels of healthcare. The island of Crete provides suitable settings for this task due to its stable, genetically homogeneous and geographically isolated population of ~0.6M inhabitants. Aim i) to estimate the prevalence and incidence of SLE in Crete over the period of 1999-2013, including temporal trends, variation with age, gender and residency; ii) to describe the clinical burden at the community level. Patients and Methods A database for surveillance was employed with multisource case finding and comprehensive data synthesis, which included medical records, patients questionnaires and administrative databases. SLE cases fulfilling the ACR 1997 classification criteria (primary definition), with physician-based diagnosis (secondary definition), or fulfilling the SLICC 2012 criteria (third definition), aged ≥15years and residing in Crete were included. Direct standardization was performed using the European Standard Population for the estimation of age-adjusted and sex-adjusted rates. Validated scores (SLICC/ACR damage index, SELENA-SLEDAI2K) were also used for the clinical description of the cohort. Results The adjusted and crude prevalence (December 2013), was 123 (CI 95% 114 to 133) and 143 (CI 95% 133 to 154) per 100,000 people. Prevalence was higher in urban (165/105) versus rural population (122.6 /105). (p<0.001) The age- and sex-adjusted and crude incidence rate of SLE in Crete was 7.4 (CI 95% 6.8 to 7.9) and 8.6 (CI 95% 8.0 to 9.0) per 100,000 persons/year, respectively (Fig.1). Following increasing trends during the previous decade, SLE occurrence rates have plateaued, with physician-based diagnosis yielding slightly higher rates compared to classification-based diagnosis (Fig.2). The average age at the time of diagnosis is 43 (±15) years (range 9-81) with a female: male ratio of 13:1. One third of patients were active smokers. SLE manifestations were classified as mild, moderate and severe in 50%, 33% and 17%, respectively with men leading more severe disease. Ninety patients had biopsy-proven lupus nephritis (LN) corresponding to an adjusted prevalence 14.5 (11-17.6) per 100,000 inhabitants. LN incidence remained stable during the 15-year period (Fig.3). The adjusted prevalence of primary neuropsychiatric lupus was estimated to 9.7 (7-12) /100,000. After a mean disease duration of 7.2 (±6.6) years, 30.5% of SLE patients have accrued organ damage (SDI >0) and 4.4% of LN patients have progressed into end-stage renal disease. Figure 1. Age- and Sex- Adjusted Incidence of SLE cases (ACR-1997 based definition) per 100,000 person/years 1999-2013 Fig 2. Incidence of SLE cases (ACR-1997 based definition) per 100,000 person/years in 3y-bands, comparing 3 case definitions Conclusions: By employing a comprehensive surveillance/population-based methodology we found that SLE occurrence in Crete, Greece may be higher than previously reported in northern European regions. Further, an increased ratio of mild versus severe forms of SLE in the community is reported as opposed to tertiary settings. This context may help in optimization of public health surveillance and policies. Figure 3. Age- and Sex- Adjusted Incidence of SLE nephritis cases (biopsy-based) per 100,000 person/years 1999-2013