954 • CID 2009:48 (1 April) • HIV/AIDS
H I V / A I D S M A J O R A R T I C L E
Detection and Prediction of Active Tuberculosis
Disease by a Whole-Blood Interferon-g Release
Assay in HIV-1–Infected Individuals
Maximilian C. Aichelburg,1Armin Rieger,1Florian Breitenecker,1Katharina Pfistershammer,1Julia Tittes,1
Stephanie Eltz,1Alexander C. Aichelburg,3Georg Stingl,1Athanasios Makristathis,2and Norbert Kohrgruber1,4
1Department of Dermatology, Division of Immunology, Allergy, and Infectious Diseases, and
Division of Clinical Microbiology, Vienna General Hospital, Medical University of Vienna,
Baumgartner Ho ¨he, Otto Wagner Hospital, and
2Department of Hygiene and Medical Microbiology,
3Medical Department Pulmological Centre SMZ
4Department of Dermatology and Venerology, Wilhelminen Hospital, Vienna, Austria
in individuals infected with human immunodeficiency virus type 1 (HIV-1) has as yet not been determined.
In this prospective, longitudinal, single-center study, 830 HIV-1–infected patients underwent testing
with the QuantiFERON-TB Gold In-Tube (QFT-GIT) assay. Clinicalscreeningforactivetuberculosiswasperformed
at least every 3 months for a median follow-up time of 19 months.
At baseline, the QFT-GIT assay yielded positive or indeterminate results in 44 (5.3%) and 47 (5.7%)
of the 830 patients, respectively. A positive QFT-GIT assay result occurred at significantly higher frequenciesamong
black individuals than among white individuals (odds ratio, 4.84; 95% confidence interval, 2.25–9.97;
among patients from Africa than among patients from Austria (odds ratio, 6.57; 95% confidence interval, 2.99–
14.25; ), and among patients from high-prevalence countries than among patients from low-prevalenceP ! .001
countries (odds ratio, 5.86; 95% confidence interval, 2.41–13.44;
GIT assay results, both median actual and nadir CD4+T cell counts were significantly lower than in patients with
interpretable QFT-GIT assay results ( ). At the time of baseline QFT-GIT screening, active tuberculosis wasP ! .001
found in 7 (15.9%) of 44 individuals with a positive result and in 1 (0.1%) of 739 patients with a negative result.
During the follow-up period, however, progression to active tuberculosis occurred exclusively in patients with a
positive QFT-GIT assay result, at a rate of 8.1% (3 of 37 patients;
QFT-GIT assay for active tuberculosis was 90.9% (95% confidence interval, 62.3%–98.4%).
Our results suggest that the QFT-GIT assay may be a sensitivetoolforthedetectionandprediction
of active tuberculosis in HIV-1–infected individuals.
The sensitivity of whole-blood interferon-g release assays to detect or predict active tuberculosis
),P ! .001
). In patients with indeterminate QFT-P ! .001
). Collectively, the sensitivity of theP ! .001
Tuberculosis is the most prevalentopportunisticdisease
in HIV-1–infected individuals [1, 2]. The rate of pro-
gression from latent Mycobacterium tuberculosis infec-
tion to active tuberculosis disease is increased and the
course of active tuberculosis is more aggressive in HIV-
Received 30 July 2008; accepted 15 November 2008; electronically published
26 February 2009.
Presented in part: 4th International AIDS Society Conference on HIV
Pathogenesis, Treatment, and Prevention, Sydney, Australia, 22–25 July 2007
Reprints or correspondence: Dr. Norbert Kohrgruber, Dept. of Dermatology, Div.
of Immunology, Allergy, and Infectious Diseases, Vienna General Hospital, Medical
University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria
Clinical Infectious Diseases 2009;48:954–62
? 2009 by the Infectious Diseases Society of America. All rights reserved.
1–infected patients, even if they are receiving effective
antiretroviral therapy [3, 4]. Conversely, active tuber-
culosis accelerates the course of HIV-1 disease .
Thus, effective screening for tuberculosis in HIV-1–
infected patients is mandatory. Individuals with latent
M. tuberculosis infection may benefit from chemopre-
vention, which mitigates the risk of subsequent active
tuberculosis development .
Traditionally, the tuberculin skin test has been the
method of choice for the diagnosis of latent M. tuber-
culosis infection . The tuberculin skin test is based
on an in vivo delayed-type hypersensitivity response to
tuberculin purified protein derivative.However,thetest
is of limited clinical value because of cross-reactivity
with nontuberculous mycobacteria and bacille Cal-
mette-Gue ´rin , sensitization and boostering on re-
petitive testing , and low sensitivity among HIV-1–
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HIV/AIDS • CID 2009:48 (1 April) • 955
infected patients [10, 11]. In addition, the test criticallydepends
on the cooperation of the patients  and on interpretation
of the results by health care professionals.
The identification of M. tuberculosis–specific antigens has led
to the development of promising alternative tools for the de-
tection of latent M. tuberculosis infection and active tubercu-
losis. These rapid whole-blood tests use ELISAs or enzyme-
linked immunosorbent spot assays tomeasuretheIFN-grelease
of sensitized T lymphocytes in response to previously encoun-
tered mycobacterial antigens . Cross-reactivity has been
reported for Mycobacterium marinum and Mycobacterium kan-
sasii  but not for Mycobacterium avium and bacille Cal-
mette-Gue ´rin. The recent introduction of the IFN-g release
assays QuantiFERON-TB Gold In-Tube (QFT-GIT; Cellestis)
 and T-Spot TB (Oxford Immunotec) offers the advantage
of increased specificity [16, 17] and easier handling, which may
eventually translate into improved screening efficacy.
It has been shown that IFN-g release assays are more useful
diagnostic tools for tuberculous infection than tuberculin skin
test in immunocompromised patients with suspected active tu-
berculosis . Nevertheless, currently available IFN-g release
assays are not sensitive enough to exclude active tuberculosis
[19–21]. Studies comparing the sensitivity of IFN-g release as-
says and the tuberculin skin test to detect active tuberculosis
in HIV-1–infected individuals have demonstrated a better per-
formance of IFN-g release assays [22, 23]. However, the value
of IFN-g release assays for the detectionandpredictionofactive
tuberculosis in HIV-1–infected individuals has not yet been
The objectives of this prospective, longitudinal cohort study
were to determine (1) clinical and epidemiological risk factors
for positive results of the QFT-GIT assay, (2) the sensitivity to
detect active tuberculosis cases by QFT-GIT assay, and (3) the
predictive value of the QFT-GIT assay for the development of
subsequent active tuberculosis in a multiethnic cohort of HIV-
1–infected individuals in a low-incidence country.
MATERIAL AND METHODS
versity of Vienna Research Ethics Committee in accordance
with the Helsinki Declaration . From May 2006 through
October 2007, HIV-1–infected patients attending the HIV Unit
of the Vienna General Hospital were asked to participate in
this study and wereprospectivelyenrolled.Afterprovidingwrit-
ten informed consent, all included patients underwent testing
with 1 QFT-GIT assay, completed a questionnaire, and were
clinically monitored for tuberculosis-related clinical symptoms
at baseline and at least every 3 months thereafter. This mon-
itoring included the assessment of pulmonary symptoms, such
as productive or nonproductive cough, hemoptysis, dyspnea
and chest pain, recent weight loss, night sweats, fever, and/or
This study was approved by the Medical Uni-
loss of appetite. During the quarterly checkup, HIV-1 disease
and treatment-related parameters, such as CD4+T cell count,
viral load, and comorbidities, were assessed. In addition, the
history of latent M. tuberculosis infection–related risk factors
was collected, including previous active tuberculosis episodes,
contact with an index case with active tuberculosis, and origin
from or travel of ?1-week duration within the past year before
inclusion to a country with an indicated tuberculosis burden
of 125 cases per 100,000 inhabitants according to World Health
Organization classification .
In the case of a positive QFT-GIT assay result, chest radi-
ography examination and/or computed tomography of the
chest and abdomen were performed. Sputum samples collected
in the morning of 3 different days and blood, stool, and urine
samples were obtained for M. tuberculosis culture and PCR.
Sputum and/or bronchial alveolar lavage samples were stained
using the Ziehl-Neelsen method for acid-fast bacteria. In ad-
dition, a tuberculin skin test was administered using the Man-
toux method with 0.1 mL (2 tuberculin units) of purified pro-
tein derivative RT23 (Statens Serum Institute). Tuberculin
reactivity was interpreted at 48 and 72 h after placement by
trained and experienced nurses. A positive tuberculin skin test
result was defined as an induration of ?5 mm, in accordance
with American Thoracic Societyguidelinesandirrespective
of bacille Calmette-Gue ´rin vaccination status.
The cohort was observed until 1 May 2008, with a focus on
active tuberculosis development. Patients with positive QFT-
GIT assay results without evidence of active tuberculosis at
baseline were informed about tuberculosis-specific symptoms
and the option of prophylactic tuberculosis treatment. All pa-
tients declined treatment and were instructed on symptom-
specific self-monitoring and reporting.
Blood samples were collected in3QFT-
GIT evacuated tubes and precoated with M. tuberculosis–spe-
cific antigens (ESAT-6, CFP-10, and TB7.7) for the test, phy-
tohemagglutinin for the positive control, or no antigen for the
negative control. Within 4 h of collection, specimens were pro-
cessed according to the manufacturer’s instructions . The
result was considered to be positive when the level of IFN-g
in the tuberculosis antigen–exposed sample minus the level in
the negative control was ?0.35 IU/mL and ?25% of the IFN-
g concentration in the negative-control plasma. Indeterminate
results were defined as either (1) an unprovoked IFN-g level
of ?8.0 IU/mL in the negative-control plasma or (2) a IFN-g
response of ?0.5 IU/mL on phytohemagglutinin stimulation
with a level of IFN-g in the tuberculosis antigen–exposed sam-
ple minus the level in the negative control of either !0.35 IU/
mL or !25% of the IFN-g concentrationinthenegative-control
HIV-related data were collected and
retrieved from the Austrian HIV Cohort Data Management
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962 • CID 2009:48 (1 April) • HIV/AIDS
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