Dual sequential testing for latent tuberculosis infection in BCG-vaccinated contacts: is it worth it?

A pillar of the WHO End TB Strategy is targeted latent tuberculosis infection (LTBI) testing to identify persons who would benefit from TB preventive treatment (TPT).1 The WHO recommends the interferon-gamma release assays (IGRAs), tuberculin skin test (TST) or Mycobacterium tuberculosis antigen-based skin tests without preference, for LTBI detection in persons at high risk for recent TB infection or of progression to active disease,2 whereas guidelines from low TB incidence/high income countries preferentially recommend the IGRAs over the TST especially in those who have received BCG vaccination or who are not likely to return for TST reading.3 Both TST and IGRAs have shown similar (although disappointingly low) positive predictive values for progression to TB disease in meta-analyses which included subjects from a variety of settings and population subgroups (eg, contacts, healthcare workers, immunosuppressed persons and migrants).4 5 The IGRAs have several advantages over the TST, namely its superior specificity in BCG-vaccinated persons, a machine readout …