Is the T-Cell-Based Interferon-Gamma Releasing Assay Feasible for Diagnosis of Latent Tuberculosis Infection in an Intermediate Tuberculosis-Burden Country?

The diagnosis of active and latent tuberculosis infection (LTBI) remains a challenge, especially in light of the fact that the tuberculin skin test (TST), which has been used to diagnose LTBI for over a century, has many well-known drawbacks This study aimed to compare the diagnostic performance of the T-cell-based interferon-gamma releasing assay (IGRA) T-SPOT TB with the TST for the diagnosis of LTBI in an intermediate tuberculosis (TB)-burden country with high BCG coverage For this purpose, a total of 91 participants, including culture-confirmed TB patients, healthy contacts known to have been exposed to Mycobacterium tuberculosis, and healthy volunteers, selected from a BCG-vaccinated population were recruited The sensitivities of the T-SPOT TB and TST were 79 3 and 25 8%, and the specificities were 75 9 and 56 7%, respectively The negative- and positive-predictive values for T-SPOT TB and TST were 78 6 and 76 7% and 42 5 and 38 1%, respectively The diagnostic performance of the TST in LTBI diagnosis is therefore severely diminished in BCG-vaccinated populations, with the sensitivity and specificity of the T-SPOT TB assay being markedly higher IGRAs have been reported to have higher diagnostic sensitivity and specificity in low TB-incidence settings than those seen here Further larger scale studies in high and intermediate TB-incidence settings are therefore warranted