In this prospective, longitudinal study on 948 HIV-1-infected patients, subjects with an indeterminate IFN-γ (gamma interferon) release assay (IGRA) result at baseline were at significantly higher risk of developing AIDS-defining manifestations other than tuberculosis (TB) irrespective of CD4(+) T cell count. Thus, in HIV-1-infected patients with advanced quantitative CD4(+) T cell depletion, an indeterminate IGRA might indicate an additional loss of global T cell function, warranting detailed clinical evaluation and careful follow-up.