COMBINED GA-67-CITRATE AND TC-99(M)-HUMAN IMMUNOGLOBULIN IMAGING IN HUMAN IMMUNODEFICIENCY VIRUS-POSITIVE PATIENTS WITH FEVER OF UNDETERMINED ORIGIN

Patients infected with the human immunodeficiency virus (HIV) suffer from seriou and life-threatening infections. These patients often present with pyrexia but without localizing signs. Despite its high sensitivity in identifying focal infection Ga-67 citrate scintigraphy lacks specificity; lymphoma and solid tumours may also be imaged. This presents particular problems in HIV-positive patients with pyrexia where the differential diagnosis is often between infection and lymphoma. In an attempt to improve the specificity of radionuclide imaging in these patients a combination of Ga-67 citrate and the new agent Tc-99m-labelled human immunoglobulin (Tc-99m-HIG) was used in 25 patients who were sequentially imaged with the two agents. Fourteen patients had 29 sites of microbiologically confirmed infection; Ga-67 citrate identified 27 sites and Tc-99m-HIG identified 16 sites. Seven of the nine sites visualized with Tc-99m-HIG, but positive with Ga-67 citrate, were intrathoracic. Abnormal concentration of Ga-67 citrate, not due to infection, occurred at eight sites; five lymphoma, one gout, one recent fracture and one patient with prominent bone marrow islands. Tc-99m-HIG showed increased concentration of tracer in only one of the patients with lymphoma. A combination of Ga-67 citrate and Tc-99m-HIG imaging in HIV-positive patients with pyrexia of unknown origin enables a differentiation between infection and lymphoma to be made more readily. The poor sensitivity of Tc-99m-HIG in the chest will limit its sole use in this patient group.