BACKGROUND: Platelets (PLTs) can be frozen with 6 percent dimethyl sulfoxide (DMSO) at −80°C for up to 2 years. This method has been modified by concentrating the PLTs and removing the supernatant before freezing.
STUDY DESIGN AND METHODS: High-yield leukoreduced PLTs stored at 22°C for up to 5 days were divided into three equal volumes: one was frozen with 6 percent DMSO at −80°C, thawed, washed, and resuspended in plasma (old method with DMSO); the second was treated with 6 percent DMSO, concentrated to remove the supernatant DMSO, frozen at −80°C, thawed, and diluted with 0.9 percent NaCl (new method with DMSO); and the third was treated with 0.9 percent NaCl without DMSO, concentrated to remove the supernatant solution, frozen at −80°C, thawed, and diluted with 0.9 percent NaCl (new method without DMSO).
RESULTS: Freeze-thaw-wash recovery of PLTs frozen by the old method with DMSO was 74 ± 2 percent with 5 percent PLT microparticles. Freeze-thaw recovery was 94 ± 2 percent with 7 percent PLT microparticles (new method with DMSO) and 69 ± 9 percent with 15 percent PLT microparticles (new method without DMSO). Total DMSO in washed PLTs was 400 and 600 mg in PLTs concentrated before freezing. In vivo recovery of PLTs frozen by the new method with DMSO and transfused into normal volunteers was 30 percent and the life span was 7 days.
CONCLUSION: Concentrating PLTs before freezing simplified the procedure by eliminating postthaw washing. PLTs frozen by this method had more PLTs with reduced GPIb and increased annexin V binding than those frozen by the old method.