Latent Tuberculosis Infection Screening and 2-Year Outcome in Antiretroviral-Naive HIV-Infected Patients in a Low-Prevalence Country.

BACKGROUND

Diagnosis and treatment of latent tuberculous infection decrease the incidence of tuberculosis (TB) in HIV-infected patients.

OBJECTIVES

To evaluate the diagnostic yield of two IFN-γ release assays and tuberculin skin testing for the screening of latent infection in HIV-infected patients.

METHODS

We performed a prospective study in 29 referral centers for HIV care in France. Asymptomatic, antiretroviral-naive patients infected with HIV-1 who consented to participate underwent two commercial tests (T-SPOT.TB and QuantiFERON-TB Gold In-Tube ELISA test [QFT]) and skin test at enrollment and were followed up for clinical events during 24 months.

RESULTS

Between March 2009 and 2011, 506 patients were included, of whom 415 performed the three tests. Median age was 38 years (interquartile range, 31-45 yr), with median CD4 cell count of 466/μL (337-615 μL), and HIV viral load of 4.5 log10 copies/ml (3.6-4.9 log10 copies/ml). At least one IFN-γ release assay was positive for 55 (13.5%) patients: QFT (n = 43), T-SPOT.TB (n = 34), both (n = 22). Skin test was positive (>5 mm) in 66 (15.9%) patients, with intertest agreement at 81 to 86%. On multivariate analysis, positive IFN-γ release assay was only correlated with country of birth (8.4% for France vs. 17.9% for high-prevalence countries, P = 0.004). Of the 55 patients with positive IFN-γ release assay, 8 (14.5%) developed active TB, all within 120 days. No other case of active TB was diagnosed. Once active TB was excluded, IFN-γ release assay-based latent infection prevalence was 11.8%.

CONCLUSIONS

Systematic screening for latent TB infection by IFN-γ release assay identifies a population at high risk of active TB over the next months. An extensive diagnostic work-up for active TB must follow positive IFN-γ release assay, before considering treatment of latent infection. Clinical trial registered with www.clinicaltrials.gov (NCT00805272).