Effect of temperature on plasma freezing under industrial conditions

The European Pharmacopoeia monograph on Human plasma for fractionation does not define the freezing process time but does define the freezing temperature (- 30 degrees C or below). Initial freezing conditions are crucial for the quality of plasma. These conditions were intended to preserve labile proteins such as fVIIl, but they can also be considered favourable for the plasma quality in general. This study evaluates the way the industrial plasma freezing affects labile coagulation factors. We have studied the freezing of plasma in industrial-size chambers at temperatures close to - 30 degrees C, - 25 degrees C and - 20 degrees C, and the possible differences between performing the freezing process in a chamber or in a freezer, in order to elucidate whether or not these parameters affect the quality of plasma. For this study, plasma bottles were frozen in industrial chambers set at - 30 degrees C, - 25 degrees C and - 20 degrees C, and in a freezer set at - 20 degrees C. The freezing rates were followed by means of probes in plasma control bottles. From this plasma, coagulation factors (fVIII, fIX and fibrinogen) were analysed before and after freezing, and cryoprecipitate was obtained in some cases. Statistically significant differences exist in fVIII:C recovery in thawed plasma between freezing at - 30 degrees C and at - 20 degrees C (n = 11; 85.4 +/- 4.3 % versus 74.6 +/- 6.0 % (chamber) or 79.3 +/- 6.3 % (freezer)). There is no difference between - 30 degrees C and - 25 degrees C, or between freezing at - 20 degrees C in a chamber or in a freezer. No significant loss of activity in thawed plasma is observed for fIX and fibrinogen at - 25 degrees C or - 20 degrees C versus - 30 degrees C. The fVIII and vWF recovery in cryoprecipitates does not show differences (464.2 IU fVIII/ml at - 30 degrees C, 446.7 IU fVIII/ml at - 25 degrees C, and 475.8 IU fVIII/ml at - 20 degrees C). The results obtained from this study support that plasma might also be frozen at - 25 degrees C or below without any impact on its quality, and that sporadic and short term deviations, from - 30 degrees C or below up to - 25 degrees C, in the currently required freezing temperature, would not have an effect on the labile factors recovery.