QuantiFERON-TB Gold test in the identification of latent tuberculosis infection in immigrants.
BACKGROUND
The identification and treatment of latent tuberculosis infection (LTBI) among immigrants are an effective strategy for TB control in developed countries. A new test for LTBI identification that uses more specific antigens of Mycobacterium tuberculosis is now commercially available under the brand name of QuantiFERON-TB Gold test.


OBJECTIVE
To compare QuantiFERON-TB Gold test to tuberculin skin testing (TST) for the detection of LTBI among immigrants from high endemic TB areas.


METHODS
Undocumented immigrants attending a district medical center were enrolled if they originated from high endemic TB areas, the time of arrival in Italy was < or = 5 years, had neither active TB disease nor known immunodeficiency status. The TST was applied according to standards and QuantiFERON-TB Gold test was performed following the manufacturer's instructions.


RESULTS
Hundred subjects were included in the comparative analysis. TST was positive in 44% of subjects; 15% had a positive QuantiFERON-TB Gold test result. The total agreement between TST and QuantiFERON-TB Gold test was 71%, for a kappa statistics of 0.37; agreement was 100% for TST negative results, but only 34% for TST positive ones. In the multivariate logistic regression analysis, previous BCG vaccination was independently associated with a lower chance of disagreement between the tests.


CONCLUSIONS
The prevalence of LTBI among immigrants was lower when determined by QuantiFERON-TB Gold; this may be a consequence of more specific MTB antigens used. Our results suggest that QuantiFERON-TB Gold may be used as confirmatory test for TST positive immigrants candidate to preventive therapy.
Carvalho
Anna C C
AC
Institute of Infectious and Tropical Diseases, University of Brescia, Piazza Spedali Civili 1, 25125 Brescia, Italy. a.carvalho@libero.it
Pezzoli
Maria Chiara
MC
El-Hamad
Issa
I
Arce
Patricia
P
Bigoni
Sara
S
Scarcella
Carmelo
C
Indelicato
Anna Maria
AM
Scolari
Carla
C
Carosi
Giampiero
G
Matteelli
Alberto
A
D000328:Adult; D004641:Emigration and Immigration / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007558:Italy / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011933:Reagent Kits, Diagnostic; D012882:Skin Tests; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology
D011933:Reagent Kits, Diagnostic