Comparison of leukocytes labeled with indium-111-2-mercaptopyridine-N-oxide and indium-111 oxine for abscess detection

Indium-111 leukocyte scanning has evolved into a practical and highly accurate method for the identification of infectious and inflammatory processes. The most commonly used agent for labeling leukocytes has been (/sup 111/In)oxine. We have investigated a newer agent, 2-mercaptopyridine-N-oxide (Merc) at our institution which unlike oxine, allows us to label leukocytes in plasma, using a simple kit procedure. Of the 92 consecutive patients referred for detection or localization of an infectious process, autologous leukocytes of 55 patients were labeled with (/sup 111/In)Merc, while those of the remaining 37 patients were labeled with (/sup 111/In)oxine. The sensitivities for Merc and oxine procedures were 87% and 92%, respectively, while the respective specificities were 100% and 92%. We conclude that the (/sup 111/In)Merc-labeled leukocytes are equally effective as (/sup 111/In)oxine-labeled leukocytes in detecting infectious processes. The use of (/sup 111/In)Merc is advantageous over (111In)oxine for white blood cell labeling because of its easier preparation.