Preservation of Dried and Frozen Plasma Over a Ten-Year Period

Abstract

76 specimens of plasma preserved in the dried or frozen state at -20 to -25[degree]C for periods up to 10 yrs. were studied to determine the effect of storage on various properties. The studies carried out on the dried plasma and the effects noted are as follows: The residual moisture was below 1% in 22 samples, between 1 and 2% in 8 samples and 2.3% in 1 sample. The stability of globin restored to the liquid state was good, with no changes attributable to length of storage noted. The pH remained in the range expected for the material. The turbidity showed no significant change. The prothrombin activity measured with the 1-stage method appears to remain unchanged for 5 yrs. After this period of time it slowly declines. The viscosity showed no relationship to length of storage. The concn. of total protein, albumin and globulin appears to be within the expected limits for this material. The content of complement appeared to be uniformly unchanged. Only an occasional specimen stored for 10-yrs. showed slight loss of complement. Plasma preserved in the frozen state between -20 and -25[degree]C but with occasional short periods of warming up to -15[degree]C appeared even better preserved than plasma for periods up to 6 yrs. After this time a slight decline in prothrombin activity was noted. Extensive clinical studies showed that plasma can be satisfactorily used after periods of storage up to at least 10 yrs. either in the frozen or dried state. No substantial difference was found between plasma prepd. from plain citrated blood and plasma prepared from ACD blood.