Objective: To evaluate the interferon-γ-releasing assays QuantiFERON-tuberculosis (TB) Gold and T-SPOT.TB in addition to tuberculin skin test (TST) for diagnosis of latent tuberculosis infection in HIV patients.
Design, setting and participants: Prospective cross-sectional study for asymptomatic HIV-infected outpatients from a large University hospital.
Intervention: Simultaneous performance of QuantiFERON-TB Gold, T-SPOT.TB and TST.
Main outcome measures: Incidence and risk factors for a positive test reaction and the concordance (κ) between the tests were investigated.
Results: Of 286 enrolled patients, 81% were men; median age was 44 years, the median CD4 cell count 408/μl (range 7–1510) with a median nadir of 126/μl (range 0–749). A number of patients (63.8%) had undetectable HIV RNA (<50 copies/ml). Both T-SPOT.TB and QuantiFERON-TB showed more positive test results than TST: 25.2 and 20.0% (P = 0.133) compared with 12.8% (P < 0.001 and P = 0.008, respectively). Agreement between T-SPOT.TB and TST (κ = 0.201) respectively QuantiFERON-TB and TST (κ = 0.335) was fair, but only poor between the serological assays (κ = 0.146). T-SPOT.TB provided more indeterminate results than QuantiFERON-TB (8 vs. 1/256, P < 0.01). Patients with a positive QuantiFERON-TB result had higher median CD4 cell counts (457 vs. 405 cells/μl for patients with negative result, P = 0.044); the amount of released interferon-γ correlated with CD4 cell counts (ρ = 0.199; P < 0.002). T-SPOT.TB results were independent from CD4 cell counts.
Conclusion: In HIV-infected patients from a low prevalence TB country, both interferon-γ assays are more sensitive than TST, but seem to be less sensitive than in immunocompetent patients. The blood tests show poor agreement and differ in their dependence on the CD4 cell count.
bTropical Medicine and Infectious Diseases, Medical Department II, Germany
cDepartment of Laboratory Medicine, Medical Center, Hospital of the Johann Wolfgang Goethe-University, Germany
dPublic Health Office, City of Frankfurt, Germany.
Received 18 June, 2008
Revised 11 August, 2008
Accepted 8 September, 2008
Correspondence to Christoph Stephan, MD, HIVCENTER at Medical Department II, Bldg. no. 68, Hospital of the Johann Wolfgang Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany. Tel: +49 69 6301 7680; fax: +49 69 6301 83425; e-mail: C.Stephan@em.uni-frankfurt.de