Interferon-gamma and immunoglobulins in latent tuberculosis infection.
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.
Topić
Renata Zrinski
RZ
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
Dodig
Slavica
S
Zoricić-Letoja
Ivka
I
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
D007136:Immunoglobulins; D007371:Interferon-gamma; D002097:C-Reactive Protein