Lawn in Lancet - the gold standard diagnostic for latent TB is IGRA

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For the past century, the tuberculin skin test has been the only screen available for the diagnosis of latent infection with tuberculosis. Its major failing is its inability to reliably distinguish individuals infected with M tuberculosis from individuals sensitised to other mycobacteria, including BCG. A decade ago the interferon-γ release assays (IGRAs) were developed whereby interferon-γ titres were measured after in-vitro stimulation of peripheral blood mono - nuclear cells with antigens such as ESAT-6 and CFP-10 (immunodominant antigens expressed by members of the M tuberculosis complex).  These have now become the gold standard for identifying individuals whose immune system has previously encountered M tuberculosis.

It would appear that the authors are well qualified, Stephen D. Lawn's profile is here and Alimuddin I Zumla's profile here.