Comparison of an interferon-gamma release assay with tuberculin skin testing in HIV-infected individuals.
BACKGROUND
Although interferon (IFN)-gamma release assays are approved for the diagnosis of latent tuberculosis infection (LTBI), limited data exist regarding their performance in HIV infection.


OBJECTIVE
To compare tuberculin skin test (TST) results to the commercial IFN-gamma release assay QuantiFERON-TB Gold In-Tube (QFT) for the diagnosis of LTBI in HIV-infected adults.


METHODS
A total of 294 HIV-infected subjects sampled from two San Francisco cohorts underwent TST, using 5 TU of purified protein derivative, and QFT, measuring IFN-gamma response to Mycobacterium tuberculosis-specific RD-1 antigens.


RESULTS
Of 294 participants, 205 (70%) returned for an evaluable TST. Concordance between QFT and TST was 89.3% (kappa=0.37, p=0.007). However, in subjects with positive test results by either TST or QFT, only 28% (8/29) had positive test results by both modalities. TST-positive/QFT-negative discordant results were found in 5.1% of subjects and TST-negative/QFT-positive discordance in 5.6%. Indeterminate QFT results occurred in 5.1%, all due to a failure to respond to the phytohemagglutinin-positive control. Subjects with a CD4(+) count of less than 100 cells/mm(3) had a relative risk of an indeterminate result of 4.24 (95% confidence interval, 1.55-11.61; p=0.003) compared with those with a CD4(+) count of 100 or more.


CONCLUSIONS
Overall concordance between QFT and TST in HIV infection was high, but agreement among subjects with positive tests by either modality was low.
Luetkemeyer
Annie F
AF
HIV/AIDS Division, San Francisco General Hospital, University of California at San Fracisco, San Francisco, Box 0874, Building 80, 995 Potrero Avenue, San Francisco, CA 94110, USA. aluetkemeyer@php.ucsf.edu
Charlebois
Edwin D
ED
Flores
Laura L
LL
Bangsberg
David R
DR
Deeks
Steven G
SG
Martin
Jeffrey N
JN
Havlir
Diane V
DV
D000328:Adult; D002353:Carrier State; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D015658:HIV Infections / Q000097:blood* / Q000150:complications; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D014374:Tuberculin Test; D014376:Tuberculosis / Q000097:blood* / Q000150:complications / Q000175:diagnosis*; D014504:Urban Health
D007371:Interferon-gamma