Evaluating latent tuberculosis infection diagnostics using latent class analysis

Background Lack of a gold standard for latent TB infection has precluded direct measurement of test characteristics of the tuberculin skin test and interferon- release assays (QuantiFERON Gold In-Tube and T-SPOT.TB). Objective We estimated test sensitivity/specificity and latent TB infection prevalence in a prospective, US-based cohort of 10740 participants at high risk for latent infection. Methods Bayesian latent class analysis was used to estimate test sensitivity/specificity and latent TB infection prevalence among subgroups based on age, foreign birth outside the USA and HIV infection. Results Latent TB infection prevalence varied from 4.0% among foreign-born, HIV-seronegative persons aged <5 years to 34.0% among foreign-born, HIV-seronegative persons aged 5 years. Test sensitivity ranged from 45.8% for the T-SPOT.TB among foreign-born, HIV-seropositive persons aged 5 years to 80.7% for the tuberculin skin test among foreign-born, HIV-seronegative persons aged 5 years. The skin test was less specific than either interferon- release assay, particularly among foreign-born populations (eg, the skin test had 70.0% specificity among foreign-born, HIV-seronegative persons aged 5 years vs 98.5% and 99.3% specificity for the QuantiFERON and T-SPOT.TB, respectively). The tuberculin skin test's positive predictive value ranged from 10.0% among foreign-born children aged <5 years to 69.2% among foreign-born, HIV-seropositive persons aged 5 years; the positive predictive values of the QuantiFERON (41.4%) and T-SPOT.TB (77.5%) were also low among US-born, HIV-seropositive persons aged 5 years. Conclusions These data reinforce guidelines preferring interferon- release assays for foreign-born populations and recommending against screening populations at low risk for latent TB infection. Trial registration number NCT01622140.