title: Risk of Infections Among 2100 Individuals with IgA Deficiency: a Nationwide Cohort Study.
abstract: OBJECTIVE
  To explore the risk of infections in individuals with IgA deficiency compared to general population controls.
  
  
  METHODS
  In this nationwide prospective population-based cohort study, we used data on IgA levels (<0.07 g/L) from six university hospitals in Sweden to identify 2100 individuals with IgA deficiency. Individuals were diagnosed between 1980 and 2010. For each patient with IgA deficiency we identified 10 controls from the general population, matched on age, sex, and place of residence (n = 18,653). Data on infections were obtained from the Swedish National Patient Register (including inpatient and hospital-based outpatient care) between 2001 and 2010. We defined infections as having a record of a relevant international classification of disease (ICD) code. Prevalences and prevalence ratios (PRs) were calculated.
  
  
  RESULTS
  Individuals with IgA deficiency were more likely to have a record of any infection (36.1 vs. 18.8% in controls) corresponding to a PR of 2.4 (95%CI 2.2-2.6). We also noted statistically significant associations with IgA deficiency (all P-values <0.05) and respiratory tract infections (17.8 vs. 6.3% in controls; PR = 3.2), gastrointestinal infections (6.0 vs. 1.8% in controls; PR = 3.5), skin infections (4.1 vs. 2.2% in controls; PR = 1.9), joint infections (0.48 vs. 0.24% in controls; PR = 2.0; P = 0.052), sepsis (1.5 vs. 0.45% in controls; PR = 3.4), meningitis (0.38 vs. 0.12%, PR = 3.2), mastoiditis/otitis (2.1 vs. 1.1% in controls; PR = 2.0), and urinary tract infections (6.1 vs. 3.4% in controls; PR = 1.8).
  
  
  CONCLUSIONS
  Individuals with IgA deficiency are at an increased risk of infections requiring hospital care.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. jonasludvigsson@yahoo.com.|Department of Paediatrics, Örebro University Hospital, Örebro University, Örebro, Sweden. jonasludvigsson@yahoo.com.|Division of Epidemiology and Public Health, School of Medicine, University of Nottingham, Nottingham, UK. jonasludvigsson@yahoo.com.
authors.forename: Jonas F
authors.initials: JF
authors.lastname: Ludvigsson
authors.affiliation: Clinical Epidemiology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Neovius
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Lennart
authors.initials: L
authors.lastname: Hammarström
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002648:Child; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D006801:Humans; D017098:IgA Deficiency / Q000150:complications* / Q000453:epidemiology*; D007239:Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011159:Population Surveillance; D015995:Prevalence; D012306:Risk; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
keywords: IgA deficiency; Immunoglobulin; Infections