Utility of the Gallium-67 Citrate Scan for the Early Diagnosis of Tuberculosis in Patients Infected with the Human Immunodeficiency Virus

Abstract

Diagnosis of tuberculosis in patients infected with the human immunodeficiency virus (HIV) is sometimes difficult because of atypical clinical and radiographic findings. The aim of this retrospective study was to determine the utility of a gallium-67 citrate scan (67Ga scan) of the chest for the early diagnosis of tuberculosis in patients infected with HIV. We selected 174 67Ga scans performed as a part of the clinical evaluation of 145 HIV-infected patients with normal pulmonary parenchyma (seen on chest radiographs) and fever of unknown origin. Scans were evaluated as to whether there was uptake in lymphoid regions (a positive 67Ga scan) or not (a negative scan). Tuberculosis was the most common condition associated with a positive 67Ga scan (48[72.7%] of 66 positive 67Ga scans). Nodal uptake had a 72.7% positive predictive value and a 92.6% negative predictive value for tuberculosis. In our experience, 67Ga scanning is a useful tool for the clinical evaluation of HIV-infected patients with unexplained fever. In areas with a high prevalence of tuberculous infection, a 67Ga scan of an HIV-infected patients that shows nodal uptake allows the clinician to initiate prompt empirical antituberculous therapy while waiting for culture results. Conversely, a 67Ga scan that does not show nodal uptake makes the diagnosis of tuberculosis unlikely.