title: Prevalence and clinical characteristics of ankylosing spondylitis in Iceland - a nationwide study.
abstract: OBJECTIVE
  To determine the prevalence and clinical characteristics of ankylosing spondylitis (AS) in the Icelandic population, which carries a high prevalence of HLA-B27.
  
  
  METHODS
  A nationwide search was performed by screening hospital records and private rheumatology services for cases of AS in association with an on-going genetic study. Individuals diagnosed with AS according to the modified New York criteria were asked to participate in the study by answering a standardised questionnaire and to undergo an interview and clinical evaluation.
  
  
  RESULTS
  A total of 256 individuals fulfilled the modified New York classification criteria for AS (169 male, 87 female); 84% of these individuals were HLA-B27 positive vs. 15% in the population (p<10-16). Of those contacted 223 patients (87.1%) answered the standardised questionnaire and were included in the study. The prevalence of AS in Iceland was 0.13% (CI 0.11-0.14%). A highly conservative prevalence number, based only on clinically evaluated patients, gave prevalence of 0.10% (CI 0.09-0.11%). Mean age at onset of symptoms was 24+/-8 years and at diagnosis 32.1+/-10.2 for male and 34.2+/-10.1 for female patients (not significant). Female patients more often had arthritis in peripheral joints and male patients were more often diagnosed with iritis. Prostatitis was experienced by 27% of male patients.
  
  
  CONCLUSIONS
  AS is less common in the Icelandic population than reported in various Caucasian populations with a similar prevalence of HLA-B27.
authors.affiliation: Department of Rheumatology, The National Hospital of Iceland, Reykjavik, Iceland.
authors.forename: Arni Jon
authors.initials: AJ
authors.lastname: Geirsson
authors.forename: Helga
authors.initials: H
authors.lastname: Eyjolfsdottir
authors.forename: Gyda
authors.initials: G
authors.lastname: Bjornsdottir
authors.forename: Kristleifur
authors.initials: K
authors.lastname: Kristjansson
authors.forename: Bjorn
authors.initials: B
authors.lastname: Gudbjornsson
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D005260:Female; D015796:HLA-B27 Antigen / Q000235:genetics*; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D015994:Incidence; D008297:Male; D015995:Prevalence; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000453:epidemiology* / Q000235:genetics* / Q000503:physiopathology; D011795:Surveys and Questionnaires; D044465:White People / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D015796:HLA-B27 Antigen