In vitro isotopic determination of diffusion volumes by transferrin labelled with indium 111. study of the correlation with SARI 125

Serum albumin labeled with iodine 125 (S.A.R.I. 125) is the reference tracer used in measuring isotopic plasma volume. It has been causing a suspension of manufacturing leading to a supply disruption and resulting in the search for an alternative to measure plasma volume under consideration for measuring blood volume. Plasma transferrin labeled with indium-111 (Tf-111In) is a potentially useful marker. To this end, we assessed the level of activity to be administered to determine a volume of distribution. The study of the correlation between the volume of distribution values obtained with S.A.R.I. 125 and Tf-111In was then performed. Tf is an autologous protein which the labelling is easy and stable. Tf-111In is a valid alternative to the S.A.R.I. 125 for measuring the plasma volume. The activity required for this examination shall not exceed 100 micro curies. (N.C.)