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JAIDS Journal of Acquired Immune Deficiency Syndromes:
doi: 10.1097/QAI.0000000000000109
Clinical Science

Latent Tuberculosis Screening Using Interferon-Gamma Release Assays in an Australian HIV-Infected Cohort: Is Routine Testing Worthwhile?

Doyle, Joseph S. MBBS, MSc, FRACP*,†,‡; Bissessor, Melanie MBChB, FRACGP§; Denholm, Justin T. BMed, MBioeth, FRACP; Ryan, Norbert BAgrSc, PhD*; Fairley, Christopher K. MBBS, FRACP, PhD§,‖; Leslie, David E. MBBS, FRCPA*

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Abstract

Background: There are limited data from high-income countries on the performance of interferon-gamma release assays in screening for latent tuberculosis infection (LTBI). We analyzed the routine application of the Quantiferon-TB Gold (QFT-G) assay to detect and predict latent and active TB among HIV-infected patients in Australia.

Methods: A retrospective cohort study included all HIV-infected patients attending the Melbourne Sexual Health Service between March 2003 and February 2011 who were screened for LTBI using QFT-G. Clinical data were analyzed in multivariable models to determine predictors for QFT-G positivity using logistic regression and active TB development using Cox proportional hazards.

Results: Nine hundred seventeen HIV-infected patients had ≥1 QFT-G performed, of whom 884 (96.4%) were negative, 29 (3.2%) positive, and 4 (0.4%) indeterminate. The mean age was 40.9 years and 88% were male, with median follow-up of 26.4 (interquartile range 15.4–30.7) months. Five hundred fifty (63%) were Australian born, whereas 198 (23%) were born in Asia or Africa. QFT-G was positive in 2.0% of Australian-born, 5.3% of overseas-born [odds ratio: 2.6, 95% confidence interval (CI): 1.2 to 5.6, P = 0.017], and 12.7% of African-born patients (odds ratio 7.1, 95% CI: 2.9 to 17.3, P < 0.001). Two cases of culture-positive TB occurred after QFT-G screening in 3.4% of QFT-G–positive and 0.1% of QFT-G–negative patients (adjusted hazard ratio: 42.4, 95% CI: 2.2 to 827, P = 0.013), a rate of 111 (95% CI: 27.8 to 445) per 100,000 person-years.

Conclusions: In this context, QFT-G has a high negative predictive (99.9%) value with few indeterminate results. A risk stratification approach to LTBI screening, where HIV-infected patients with epidemiological risk factors for TB infection undergo QFT-G testing, might be clinically appropriate and potentially cost effective in similar settings.

© 2014 by Lippincott Williams & Wilkins

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