title: Serum Concentrations of IgG4 in the Spanish Adult Population: Relationship with Age, Gender, and Atopy.
abstract: OBJECTIVE
  Serum IgG4 concentrations are commonly measured in clinical practice. The aim of this study was to investigate serum IgG4 concentrations in adults and their potential relationship with demographic, lifestyle, metabolic, and allergy-related factors.
  
  
  METHODS
  Serum IgG4 concentrations were measured with a commercial assay in 413 individuals (median age 55 years, 45% males) who were randomly selected from a general adult population.
  
  
  RESULTS
  Median IgG4 concentration was 26.8 mg/dL. Five out of the 413 individuals (1.2%) exhibited IgG4 concentrations >135 mg/dL, and 17 out of 411 (4.1%) exhibited an IgG4/total IgG ratio >8%. Serum IgG4 concentrations were significantly higher in males than in females and decreased with age. After adjusting for age and sex, serum IgG4 concentrations were not significantly influenced by alcohol consumption, smoking or common metabolic abnormalities (obesity and the related metabolic syndrome). Serum IgG4 concentrations were not significantly correlated with serum concentrations of proinflammatory cytokines and inflammation markers. Serum IgG4 concentrations were significantly correlated with IgE concentrations. Serum IgG4 concentrations tended to be higher in atopics (individuals with IgE-mediated sensitization to aeroallergens) than in non-atopics, particularly among atopics without respiratory symptoms. Serum IgG4 concentrations were not significantly correlated with total eosinophil blood count. Cases of IgG4-related disease were neither present at baseline nor detected after a median of 11 years of follow-up.
  
  
  CONCLUSIONS
  Studies aimed at defining reference IgG4 values should consider partitioning by age and sex. Further studies are needed to confirm the potential influence of atopy status on serum IgG4 concentrations.
authors.affiliation: Department of Internal Medicine, Complejo Hospitalario Universitario, Santiago de Compostela, Spain.
authors.forename: Iago
authors.initials: I
authors.lastname: Carballo
authors.affiliation: Department of Internal Medicine, Complejo Hospitalario Universitario, Santiago de Compostela, Spain.
authors.forename: Lucía
authors.initials: L
authors.lastname: Alvela
authors.affiliation: Department of Clinical Biochemistry, Complejo Hospitalario Universitario, Santiago de Compostela, Spain.
authors.forename: Luis-Fernando
authors.initials: LF
authors.lastname: Pérez
authors.affiliation: Department of Clinical Epidemiology, Complejo Hospitalario Universitario, Santiago de Compostela, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Gude
authors.affiliation: Department of Allergy, Complejo Hospitalario Universitario, Santiago de Compostela, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Vidal
authors.affiliation: Department of Internal Medicine, Complejo Hospitalario Universitario, Santiago de Compostela, Spain.|Department of Clinical Epidemiology, Complejo Hospitalario Universitario, Santiago de Compostela, Spain.
authors.forename: Manuela
authors.initials: M
authors.lastname: Alonso
authors.affiliation: Department of Internal Medicine, Complejo Hospitalario Universitario, Santiago de Compostela, Spain.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Sopeña
authors.affiliation: Department of Internal Medicine, Complejo Hospitalario Universitario, Santiago de Compostela, Spain.
authors.forename: Arturo
authors.initials: A
authors.lastname: Gonzalez-Quintela
mesh_terms: D000328:Adult; D000375:Aging / Q000097:blood*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006967:Hypersensitivity / Q000097:blood*; D007074:Immunoglobulin G / Q000097:blood*; D008297:Male; D008875:Middle Aged; D012727:Sex Characteristics; D013030:Spain
chemical_list: D007074:Immunoglobulin G