Clinical role of anti-granulocyte MoAb versus radiolabeled white blood cells.

Scintigraphy with white blood cells (WBC), labeled with ¹¹¹In-oxine or (99m)Tc-hexamethylpropyleneamine oxime (HMPAO), and anti-granulocyte scintigraphy using (99m)Tc-labeled monoclonal antibodies (MoAb), or fragments thereof, are established procedures for the diagnostic workup of infectious or inflammatory disease processes. Clinically severe afflictions such as fever of unknown origin (FUO), infectious joint replacements, osteomyelitis, vascular graft infections or cardiovascular infections often present where noninvasive proof of granulocytic inflammatory activity is more useful than mere morphology-based radiological diagnostic approaches. The labeling differences between WBC and antigranulocyte antibodies produce different pharmacokinetics and patterns of tracer accumulation and distribution. Together with the physical imaging properties of the respective isotope used for imaging, the diagnostic value of a tracer depends on the clinical setting. Thus, despite the easier and safer handling of antibody-based in-vivo labeling, indications for in-vivo labeled WBC remain. As a consequence there is as yet no ideal inflammation tracer, also bearing in mind that neither WBCs nor antibody-diagnostics can reliably differentiate sterile inflammation from infection. Although positron emission tomography (PET) using e.g. FDG-PET is replacing conventional scintigraphies in some indications, both in vivo and in vitro labelled leukocytes will remain an important clinical pillar in the diagnosis of infection and inflammation.