111In-tropolonate labelled platelets; studies in normals and in patients with thrombocytopenia.

Human platelets were labelled with aqueous 111In-tropolonate in comparison with 111In-oxinate. In normals the labelling efficiency with 111In-tropolonate was higher (93% +/- 2%) than with 111In-oxinate (67% +/- 8%) (P less than 0.05). In cases of severe thrombocytopenia, lower labelling efficiencies were obtained. In six normals a mean platelet life of 9 days +/- 3 days and an initial recovery of 59% +/- 15% were obtained. In twelve patients with thrombocytopenia the mean platelet life was 4 days +/- 4 days and the initial recovery was 58% +/- 20%. The absolute uptake of radioactivity in spleen and in liver in both groups are reported.