Diagnosing infection in febrile granulocytopenic patients with indium-111-labeled human immunoglobulin G

Delineation of focal infection is a major problem in the management of febrile granulocytopenic patients. The utility of indium-111-labeled human nonspecific immunoglobulin G (In-111-IgG), a newly developed radiopharmaceutical for imaging focal inflammation, was reported in patients with adequate WBC counts. In the present study, we investigated whether In-111-IgG scintigraphy could be used to locate infection in granulocytopenic patients. Granulocytopenic rats with focal infection were imaged after In-111-IgG injection. Thereafter, In-111-IgG scintigraphy was performed in 20 granulocytopenic patients. Images were obtained 4, 24, and 48 hours after injection of 75 mBq In-111-IgG. Scintigraphic findings were compared with clinical, roentgenologic, and ultrasonographic methods and culture results. In the animal model high In-111-IgG accumulation was observed in the infectious focus. In the patients, 13 proven pulmonary, abdominal, joint, and soft tissue infections of both bacterial and fungal origin were detected adequately. In-111-IgG uptake not due to verified inflammation was observed in the large bowel of two patients. A thoracic wall infiltrate showing only mild inflammatory activity was not detected. Small toxoplasmosis lesions in heart, liver, and kidneys were obscured by physiologic In-111-IgG activity in these organs. In-111-IgG scintigraphy is a useful technique to delineate focal infection in patients with granulocytopenia. Accumulation of the radiopharmaceutical does not appear to be granulocyte-mediated. In-111-IgG is a safe and convenient radiopharmaceutical that probably contributes to the early diagnosis of focal infection in granulocytopenic patients.