Indium-111 platelet kinetics in normal human subjects: Tropolone versus oxine methods

The effect of labeling media on the kinetics of [¹¹¹In]platelets was evaluated by performing a paired crossover study in eight normal human subjects using tropolone and oxine methods. Platelets were labeled in autologous plasma with [¹¹¹In]tropolone (In-tr) and in ACD-saline with [¹¹¹In]oxine (In-ox) and reinjected. Starting at 1 hr, ten blood samples were obtained over an 8-day period. The in vivo platelet recovery was higher at 1 hr and throughout the 8 days of study with In-tr and the gamma camera images showed less uptake in liver and spleen than with In-ox. When platelet life-span (PLS) was estimated using all ten samples, only linear regression showed that the platelet life-span was longer with In-tr (10.7 ± 1.5) than with In-ox (9.5 ± 0.8). When the PLS was estimated excluding the 1-hr sample point, the life-span of platelets was significantly longer with In-tr than with In-ox based on three out of four models of curve fitting. These results demonstrate that platelets labeled with In-tr in plasma are preserved better in circulation and have equal or longer life-span than platelets labeled with In-ox in ACD-saline.