Radiolabeled red cell viability. I. Comparison of 51Cr, 99mTc, and 111In for measuring the viability of autologous stored red cells.

The simultaneous determination of autologous 99mTc red cell (RBC) and 51Cr RBC viability at 24 hours was measured in 19 normal volunteers whose RBCs had been stored in additive media (Nutracel) for 42 or 49 days. The ratio of the 51Cr:99mTc value was 1.23. In this experiment we also calculated 51Cr RBC viability by both the single-isotope method (extrapolation) and the double-isotope method (using 125I human serum albumin for an independent plasma volume) in the same volunteers. The corresponding viability values were not significantly different. The simultaneous determination of autologous 111In-oxine RBC and 51Cr RBC viability at 24 hours was measured in 19 other normal volunteers whose RBCs had been stored in citrate-phosphate-dextrose-adenine (CPDA-1) for 1 or 15 days. The ratio of the 51Cr:111In value was 1.1. Use of these 24-hour viability ratios as conversion factors permits direct comparison of 99mTc or 111In RBC viability with a 51Cr standard, and therefore expands the application of these newer RBC radiolabels.