title: Interferon-gamma and immunoglobulins in latent tuberculosis infection.
abstract: OBJECTIVE
  The aim of the present study was to investigate the occupational risk of tuberculosis in health care workers (HCW) at a children's hospital in a middle-income country with an intermediate prevalence of tuberculosis and compulsory bacille Calmette-Guérin vaccination and to assess the association of latent tuberculosis infection (LTBI) with the concentration of immunoglobulins (IgG, IgA, IgM), C-reactive protein and hematological changes.
  
  
  METHODS
  Fifty four HCW were divided into groups according to their exposure to tuberculous patients and interferon (IFN-gamma) findings. IFN-gamma determination and tuberculin skin test (RT23) were performed in parallel.
  
  
  RESULTS
  Positive IFN-gamma results were recorded in 31% of study HCW. Higher exposure to tuberculous patients did not lead to a statistically significant increase in the rate of positive IFN-gamma findings but did increase the number of hyperreactors. HCW with positive IFN-gamma findings were 5 years older than IFN-gamma negative subjects. The median IgA concentration was 29% higher (p = 0.0233) in IFN-gamma positive subjects (2.44 g/L) as compared with IFN-gamma negative subjects (1.89 g/L).
  
  
  CONCLUSIONS
  Study results showed the prevalence of LTBI in HCW at a children's hospital to be comparable to the prevalence recorded in the general population. IFN-gamma proved to be a more reliable test to determine LTBI in a population of bacille Calmette-Guérin-vaccinated HCW. The new diagnostic approach will hopefully contribute to more rational use of x-rays and prevent unnecessary administration of chemoprophylaxis. The higher concentration of IgA in IFN-gamma-positive HCW pointed to the possible protective role of IgA antibodies in LTBI.
authors.affiliation: Department of Clinical Laboratory Diagnosis, Srebrnjak Children's Hospital, Reference Center for Clinical Pediatric Allergology of the Ministry of Health and Welfare, Zagreb, Croatia. renata.zrinski-topic@zg.t-com.hr
authors.forename: Renata Zrinski
authors.initials: RZ
authors.lastname: Topić
authors.forename: Slavica
authors.initials: S
authors.lastname: Dodig
authors.forename: Ivka
authors.initials: I
authors.lastname: Zoricić-Letoja
mesh_terms: D000328:Adult; D002097:C-Reactive Protein / Q000032:analysis; D017523:Croatia / Q000453:epidemiology; D005260:Female; D006282:Health Personnel; D006801:Humans; D007136:Immunoglobulins / Q000097:blood*; D017758:Infectious Disease Transmission, Patient-to-Professional; D007371:Interferon-gamma / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D015995:Prevalence; D014374:Tuberculin Test; D014376:Tuberculosis / Q000453:epidemiology* / Q000276:immunology* / Q000635:transmission
chemical_list: D007136:Immunoglobulins; D007371:Interferon-gamma; D002097:C-Reactive Protein