99mTc-besilesomab (ScintimunA®) in peripheral osteomyelitis: comparison with 99mTc-labelled white blood cells

The diagnosis of osteomyelitis is a challenge for diagnostic imaging. Nuclear medicine procedures including white blood cell imaging have been successfully used for the identification of bone infections. This multinational, phase III clinical study in 22 European centres was undertaken to compare anti-granulocyte imaging using the murine IgG antibody besilesomab (ScintimunA (R)) with Tc-99m-labelled white blood cells in patients with peripheral osteomyelitis. A total of 119 patients with suspected osteomyelitis of the peripheral skeleton received Tc-99m-besilesomab and Tc-99m-hexamethylpropyleneamine oxime (HMPAO)-labelled white blood cells (WBCs) in random order 2-4 days apart. Planar images were acquired at 4 and 24 h after injection. All scintigraphic images were interpreted in an off-site blinded read by three experienced physicians specialized in nuclear medicine, followed by a fourth blinded reader for adjudication. In addition, clinical follow-up information was collected and a final diagnosis was provided by the investigators and an independent truth panel. Safety data including levels of human anti-mouse antibodies (HAMA) and vital signs were recorded. The agreement in diagnosis across all three readers between ScintimunA (R) and Tc-99m-HMPAO-labelled WBCs was 0.83 (lower limit of the 95% confidence interval 0.8). Using the final diagnosis of the local investigator as a reference, ScintimunA (R) had higher sensitivity than Tc-99m-HMPAO-labelled WBCs (74.8 vs 59.0%) at slightly lower specificity (71.8 vs 79.5%, respectively). All parameters related to patient safety (laboratory data, vital signs) did not provide evidence of an elevated risk associated with the use of ScintimunA (R) except for two cases of transient hypotension. HAMA were detected in 16 of 116 patients after scan (13.8%). ScintimunA (R) imaging is accurate, efficacious and safe in the diagnosis of peripheral bone infections and provides comparable information to Tc-99m-HMPAO-labelled WBCs.