A comparative study of two different methods for the detection of latent tuberculosis in HIV-positive individuals in Chile.
OBJECTIVE
To compare the performance of two tests for diagnosing latent tuberculosis (TB) infection in the HIV-positive population in Chile, in order to better identify the subjects who might benefit from TB chemoprophylaxis.


METHODS
This was a cross-sectional study among individuals attending three HIV outpatient clinics in Santiago, tested with a 2-TU purified protein derivative, QuantiFERON((R))-TB Gold 'in-tube' (QFT-G), and a chest X-ray.


RESULTS
A total of 116 subjects were enrolled in the study, having a mean CD4 count of 393cells/microl (range 100-977). The tuberculin skin text (TST; 5mm cutoff) and QFT-G results were positive in 10.9% and 14.8% of the individuals, respectively, with moderate agreement between both tests (kappa=0.59). A history of both known TB exposure (odds ratio (OR) 3.46, 95% confidence interval (CI) 1.02-11.22) and past TB (OR 4.31, 95% CI 1.13-15.5) were associated with a positive QFT-G result. Only past TB was significantly associated with a positive TST result (OR 6.63, 95% CI 1.62-26.3). Among the subjects with TST<5mm, 8.2% were positive by QFT-G test. These individuals had a lower mean CD4 cell count than those detected positive by both tests (328cells/microl and 560cells/microl, respectively, p=0.03).


CONCLUSIONS
In this population of HIV-infected individuals, QFT-G and TST showed an acceptable level of agreement, although QFT-G appears less affected by more advanced immunosuppression.
School of Medicine, Pontificia Universidad Católica de Chile, Lira 44, Santiago, Chile. balcells@med.puc.cl
María Elvira
ME
Balcells
Carlos M
CM
Pérez
Leonardo
L
Chanqueo
Martín
M
Lasso
Marcela
M
Villanueva
Mónica
M
Espinoza
Luis
L
Villarroel
Patricia
P
García
D017088:AIDS-Related Opportunistic Infections / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology; D000328:Adult; D000368:Aged; D018791:CD4 Lymphocyte Count; D002677:Chile / Q000453:epidemiology; D005260:Female; D015658:HIV Infections / Q000150:complications* / Q000276:immunology; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology; D055815:Young Adult
D011933:Reagent Kits, Diagnostic; D007371:Interferon-gamma