Use of technetium antigranulocyte monoclonal antibody Fab' fragments for the detection of osteomyelitis

Abstract

Accurate early diagnosis of osteomyelitis is critical for optimal clinical management. Conventional radiology (X-rays, CT) and nuclear medicine scans (bone, gallium, and technetium/indium white blood cell [WBC]) have limitations and drawbacks. The monoclonal antibody (MAb) ImmuRAID^TM-MN3 (Immunomedics Inc., Morris Plains, NJ), a 99m-Tc Antigranulocyte Fab' fragment, recognizes a surface glycoprotein NCA-90/95 shared by granulocytes, carcino-embryonic antigen (CEA), and meconium antigen (MA). Intravenous injection of radiolabeled MAb enables in vivo labeling of human granulocytes and targets infected lesions in the bone and throughout the body. Technetium labeled Fab' fragments rapidly clear the blood pool and high-quality images can be obtained the same day, as early as 1 h postinjection.

Results at our institution on 13 patients with clinically suspected osteomyelitis of infected long bones, prostheses, and diabetic foot ulcers were compared with the surgical/bacteriological verification of the presence or absence of infection. The MAb scan showed six true positives, six true negatives, and one false negative (very low grade infection). The procedure was safe, no clinical or laboratory adverse reactions were encountered. The MAb fragments are markedly less immunogenic than whole IgG, resulting in lower induction of human antimouse antibody (HAMA) titers. No HAMA to this MAb fragment has been detected in 24 patients (data from multiple institutions). Our preliminary results suggest that 99m-Tc ImmuRAID^TM-MN3 is highly accurate for detection of osteomyelitis. This study is part of an on-going multiinstitutional project sponsored by Immunomedics, Inc. to evaluate the efficacy and safety of this radiopharmaceutical.