The Indeterminate Answer

A 31-year-old man presents to an HIV clinic after a new diagnosis of HIV-1 infection confirmed by fourth-generation antigen/antibody immunoassay and Western blot two weeks prior. He was referred from a community health center following a routine sexual health screening. He reports no prior HIV testing and denies any current symptoms. He has no significant past medical history and takes no medications. CD4 count is 118 cells/mcL and HIV-1 RNA is 48,500 copies/mL. He is a nonsmoker and reports no respiratory symptoms.

During the social history, he discloses that his male domestic partner of three years was diagnosed with pulmonary tuberculosis four weeks ago, confirmed by positive sputum AFB smear and culture growing pan-susceptible Mycobacterium tuberculosis. His partner has been on standard four-drug therapy for three weeks. The patient shares a one-bedroom apartment with his partner and reports no history of prior TB testing or treatment. He has never lived outside the United States and reports no international travel to TB-endemic regions.

On examination, temperature is 36.9°C, heart rate 84, blood pressure 118/74 mmHg, oxygen saturation 98% on room air. The physical examination is unremarkable. He specifically denies cough, hemoptysis, night sweats, and unintentional weight loss. A QuantiFERON-TB Gold Plus (QFT-Plus) is sent and the result returns indeterminate: the IFN-gamma response in the mitogen control tube falls below the minimum threshold required for valid interpretation, precluding a positive or negative classification. A posterior-anterior chest radiograph is obtained and is shown below.