DETERMINATION OF POST-TRANSFUSION RBC VIABILITY

Abstract

Methods for determining post-transfusion viability of stored autologous RBC's in normal adult volunteers were compared using the simultaneous administration of I-125-HSA, Cr-51-RBC's, and Tc-99m-RBC's labeled with BNL kits. Methods using a double label technique (a plasma label + an RBC label) were compared with single label techniques (RBC label only), and Cr-51-RBC results were compared to Tc-99m-RBC results. Post-infusion samples were drawn at 5, 7.5, 10, 12.5, 15, and 20 minutes and at 24 hours. Zero-time extrapolation calculations were compared with early time-averaged calculations to determine the 100% value. In addition, plasma levels of Cr-51 and Tc-99m were measured at all time periods. We found that (1) the double label technique and the single label extrapolation technique give identical results; (2) the early time-averaged methods are less accurate if there is significant loss of RBC's; (3) substitution of Tc-99m-RBC's for Cr-51-RBC's is acceptable at early times but at 24 hours they are not equivalent; Tc-99m-RBC survival at 24 hours needs to be multiplied by a factor of 1.2 to make it equivalent to Cr-51-RBC data; (4) plasma levels of Tc-99m are 2–3 times higher than Cr-51 levels at early times; at 24 hours plasma Tc-99m levels were half the early values (2% vs. 4%) but Cr-51 values were negligible (0.2%). We conclude that Tc-99m-RBC's may be used to assess post-transfusion RBC viability at 24 hours if one multiplies surviving fraction by a factor of 1.2. Either the double label technique or the single label extrapolation technique should be used.