title: Prevalence of antibodies against Chlamydia trachomatis and incidence of C. trachomatis-induced reactive arthritis in an early arthritis series in Finland in 2000.
abstract: OBJECTIVE
  To study the prevalence of different serotypes of Chlamydia trachomatis antibodies and the incidence of C. trachomatis-induced reactive arthritis (ReA) among patients with early arthritis in a defined population.
  
  
  METHODS
  Serum samples were collected from a cohort of 122 adult patients in the age group 18-65 years included in the Kuopio 2000 Arthritis Survey. Antibodies against C. trachomatis serotypes C, E, and G were studied using enzyme immunoassay (EIA) tests among patients and in a control cohort of 78 adults without any joint symptoms. The incidence assessment for Chlamydia-induced ReA was based on a ligase chain reaction (LCR) test in urine and clinical symptoms and signs appropriate for ReA.
  
  
  RESULTS
  Of 122 patients, with the baseline diagnosis of rheumatoid arthritis (RA) in 11, spondyloarthropathy (SpA) in 28, and undifferentiated arthritis (UA) in 83 cases, 42 (34%) showed immunoglobulin (Ig)G or IgA antibodies against at least one serotype C, E, or G. Among the patients with UA the prevalence was significantly increased compared with the controls (p = 0.010). C. trachomatis-induced ReA arthritis was diagnosed in only three patients with the LCR test. On this basis the incidence of C. trachomatis-induced arthritis was 5.4/100 000 [95% confidence interval (CI) 1.1-15.7] in the age group 18-65 years.
  
  
  CONCLUSIONS
  Antibodies against C. trachomatis were most common in patients with UA reflecting the fact that cases with chlamydia-induced ReA are included in this subgroup.
authors.affiliation: Kuopio Municipal Hospital, Kuopio, Finland. elina.savolainen@fimnet.fi
authors.forename: E
authors.initials: E
authors.lastname: Savolainen
authors.forename: A
authors.initials: A
authors.lastname: Kettunen
authors.forename: A
authors.initials: A
authors.lastname: Närvänen
authors.forename: H
authors.initials: H
authors.lastname: Kautiainen
authors.forename: U
authors.initials: U
authors.lastname: Kärkkäinen
authors.forename: R
authors.initials: R
authors.lastname: Luosujärvi
authors.forename: O
authors.initials: O
authors.lastname: Kaipiainen-Seppänen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016918:Arthritis, Reactive / Q000453:epidemiology* / Q000276:immunology; D016009:Chi-Square Distribution; D002690:Chlamydia Infections / Q000453:epidemiology* / Q000276:immunology; D002692:Chlamydia trachomatis / Q000276:immunology*; D015331:Cohort Studies; D005260:Female; D005387:Finland / Q000453:epidemiology; D006306:Health Surveys; D006801:Humans; D007124:Immunoenzyme Techniques; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D015995:Prevalence; D000091402:Prohibitins; D012044:Regression Analysis
chemical_list: D007070:Immunoglobulin A; D007074:Immunoglobulin G; C000717331:PHB2 protein, human; D000091402:Prohibitins