Effect of 99mTc elution in vivo from red cells on red cell volumes measured using autologous 99mTc-labeled red cells: comparison with 51Cr method

The purpose of this work was to compare the measured red-cell volume (RCV) using sodium pertechnetate [RCV-99mTc] compared to the reference technique using sodium radiochromate [RCV-51Cr] and to assess the influence of technetium-99 elution on the RCV-99mTc value. Ten patients had simultaneous measurements of RCV-99mTc and RCV-51Cr. Elution of Tc-99m from red blood cells was 2.9% and led to an average overestimation of RCV-99mTc of 3.7%. The introduction of individual tracer elution rates in the RCV-99mTc calculation corrects this overestimation.