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Open Access Highly Accessed Research article

Poor concordance between interferon-γ release assays and tuberculin skin tests in diagnosis of latent tuberculosis infection among HIV-infected individuals

Naasha J Talati1*, Ulrich Seybold12, Bianca Humphrey1, Abiola Aina1, Jane Tapia1, Paul Weinfurter3, Rachel Albalak3 and Henry M Blumberg14

Author Affiliations

1 Division of Infectious Diseases, Emory University, School of Medicine, Atlanta, GA, USA

2 Division of Infectious Diseases, Medical Policlinic, Ludwig Maximilians – University, Munich, Germany

3 Division of Tuberculosis Elimination, Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA

4 Division of Infectious Diseases, Grady Memorial Hospital, Atlanta, GA, USA

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BMC Infectious Diseases 2009, 9:15  doi:10.1186/1471-2334-9-15

Published: 10 February 2009

Abstract

Background

A new generation of diagnostic tests, the interferon-γ release assays (IGRAs), have been developed for the detection of latent tuberculosis infection (LTBI). Limited data are available on their use in HIV-infected persons.

Methods

A cross-sectional study was carried out at 2 HIV clinics in Atlanta to assess the utility of two IGRA tests (T-SPOT.TB [TSPOT] and QuantiFERON-TB Gold in Tube [QFT-3G]) compared to the tuberculin skin test (TST).

Results

336 HIV-infected persons were enrolled. Median CD4 count was 335 cells/μl and median HIV viral load was 400 copies/ml. Overall, 27 patients (8.0%) had at least 1 positive diagnostic test for LTBI: 7 (2.1%) had a positive TST; 9 (2.7%) a positive QFT-3G; and 14 (4.2%) a positive TSPOT. Agreement between the 3 diagnostic tests was poor: TST and TSPOT, [κ = 0.16, 95% CI (-0.06, 0.39)], TST and QFT-3G [κ = 0.23, 95% CI (-0.05, 0.51)], QFT-3G and TSPOT [κ = 0.06, 95% CI (-0.1, 0.2)]. An indeterminate test result occurred among 6 (1.8%) of QFT-3G and 47 (14%) of TSPOT tests. In multivariate analysis, patients with a CD4 ≤ 200 cells/μl were significantly more likely to have an indeterminate result [OR = 3.6, 95% CI (1.9, 6.8)].

Conclusion

We found a low prevalence of LTBI and poor concordance between all 3 diagnostic tests. Indeterminate test results were more likely at CD4 counts ≤ 200 cells/μl. Additional studies among HIV-infected populations with a high prevalence of TB are needed to further assess the utility of IGRAs in this patient population.