Bone marrow scintigraphy with 99m Tc labelled monoclonal anti-NCA 90 Fab' fragment: a feasibility study and comparison of bone marrow uptake with 99m Tc labelled monoclonal anti-NCA 95 antigranulocyte antibody.

The aim of this retrospective study was to evaluate the usefulness of 99mTc labelled monoclonal anti-NCA 90 antigranulocyte antibody Fab' fragment (MN3 Fab') as a bone marrow imaging agent. One hundred and ten planar scans (88 patients) of the lumbar and sacroiliac regions as well as whole-body scans were performed after 1, 5 and 24 h. All the scans were evaluated visually and bone marrow uptake was determined semiquantitatively as count density ratio from sacroiliac-minus-background to background area. Results were compared to 50 age-matched patients with normal bone marrow scans obtained with the intact 99mTc labelled monoclonal anti-NCA 95 antigranulocyte antibody (BW 250/183) in a previous study. Seventy-three patients showed a physiological activity distribution in the central bone marrow. Ten patients showed a bone marrow extension, while in two patients central bone marrow depression was observed. Evaluation of the ribs, lower thoracic and upper lumbar spine was hampered by soft-tissue activity. Bone marrow uptake was 1.36+/-0.56 after 1 h, decreased thereafter and was significantly lower than that of BW 250/183 (P < 0.001). In conclusion, MN3 Fab' cannot be recommended for bone marrow scintigraphy, because relevant parts of the haemopoietically active bone marrow are not accessible to visual evaluation. A significant role of the semiquantitative evaluation of MN3 Fab' bone marrow uptake in patients with potential marrow depression seems unlikely.