**5.3 Tc-99m labelled Anti-granulocyte antibody: Clinical utilities and applications**

Tc-99m Sulesomab is commonly indicated as an adjunctive diagnostic imaging of infection/inflammation in patients with suspected osteomyelitis, including patients with diabetic foot ulcers. As Tc-99m MDP bone scan has a low specificity, Tc-99m Sulesomab imaging as a follow-up test reduces the false-positive rate of Tc-99m MDP imaging. The overall sensitivity and specificity for the diagnosis of infections is 86% and 72%, respectively. In patients with diabetic foot ulcers, the diagnostic accuracy of Tc-99m Sulesomab compared with In-111 and Tc-99m HMPAO labelled leukocytes scanning was observed not to be significantly different (81 and 75%, respectively). However, Tc-99m Sulesomab imaging has a significantly higher sensitivity. In our own experience Tc-99m Sulesomab imaging has an incremental diagnostic value in the detection and ruling out osteomyelitis especially when used subsequent to Tc-99m MDP imaging (Figure 9).

anatomic localization of the site of infection than SPECT alone allowing differentiation between prosthesis and soft-tissue uptake. Similarly, (Bar-Shalom et al., 2006) observed that using In-111 labelled leukocyte SPECT/CT contributed to accurate identification of infection in 55% of patients suspected to have osteomyelitis and 67% of those suspected to have a

**5.1 Tc-99m labelled Anti-granulocyte antibody: Pharmacological and physiochemical** 

Three anti-granulocyte antibodies have been used including anti-NCA-95 immunoglobulin IgG, fanelosomab (a monoclonal murine M class immunoglobulin), sulesomab (a murine monoclonal antibody fragment anti-NCA-90 Fab) and anti-CD15. Presently most routinely

Leukoscan consists of a small murine monoclonal antibody fragment, sulesomab, labelled with Tc-99m. The radiolabelled antibody fragment (Fab) reacts with the normal cross reacting antigen (NCA-90) present on the surface of virtually all neutrophils. Therefore areas where neutrophils have accumulated can be detected and this proves useful in determining the location and extent of infection and inflammation. Uptake at sites of infection is therefore related to migration of antibody labelled circulating granulocytes and non-specific non-antigen related uptake of free antibody. The use of radiolabelled monoclonal antibodies against surface antigens as present on granulocytes has the advantage that labelling procedures are easier and do not require handling of potentially contaminated blood. Since the leukocytes are not removed from the patient, it is considered as in-vivo labelling process. Mounting of an immune response and production of human anti-mouse antibodies (HAMA) may pose a concern; however, in our experience and available published data the

**5.2 Tc-99m labelled Anti-granulocyte antibody: Imaging protocols and pre-requisites**  Tc-99m Sulesomab is presented as a lyophilised powder (0.31 mg per vial) to be reconstituted with sodium chloride. Approximately 555-925 MBq is injected intravenously. Imaging should be performed 1–8 hours post injection. We usually perform imaging at 10 minutes and 2-4 hours post injection with occasional 24 hour delayed imaging in certain

situations to have better target to background ratio for better delineation of lesions.

**5.3 Tc-99m labelled Anti-granulocyte antibody: Clinical utilities and applications**  Tc-99m Sulesomab is commonly indicated as an adjunctive diagnostic imaging of infection/inflammation in patients with suspected osteomyelitis, including patients with diabetic foot ulcers. As Tc-99m MDP bone scan has a low specificity, Tc-99m Sulesomab imaging as a follow-up test reduces the false-positive rate of Tc-99m MDP imaging. The overall sensitivity and specificity for the diagnosis of infections is 86% and 72%, respectively. In patients with diabetic foot ulcers, the diagnostic accuracy of Tc-99m Sulesomab compared with In-111 and Tc-99m HMPAO labelled leukocytes scanning was observed not to be significantly different (81 and 75%, respectively). However, Tc-99m Sulesomab imaging has a significantly higher sensitivity. In our own experience Tc-99m Sulesomab imaging has an incremental diagnostic value in the detection and ruling out osteomyelitis especially when

**5. Tc-99m labelled Anti-granulocyte antibody scintigraphy** 

level of adverse events and probability of HAMA response are both low.

sulesomab (Leukoscan ®) is used in clinical practice.

used subsequent to Tc-99m MDP imaging (Figure 9).

vascular graft infection.

**characteristics** 

Tc-99m fanolesomab has been used for diagnosis of acute appendicitis. It has a good overall accuracy with a positive predictive value (PPV) of 74-87% and a negative predictive value (NPV) between 95-100%. A high NPV is helpful for the patients to avoid unnecessary surgery, however, a number of false positives have been an issue with this radiopharmaceutical.

Fig. 9. A 10-year old girl, presented with tenderness and swelling at right distal femur. Tc-99m MDP bone scan show hyperperfusion and increases tracer accumulation at the distal 1/3rd of right femur. Tc-99m Sulesomab imaging show increased tracer uptake at distal right femur corresponding to the site seen on bone scan, confirming osteomyelitis.
