Dr R. Moog, Münchener Blutbank GmbH, Nymphenburger Str.1, D-80335 München, Germany E-mail: email@example.com
Fresh frozen plasma (FFP) should be stored at temperatures > −30°C according to national and international guidelines to maintain the stability of clotting factors and inhibitors. In the present report, FFP was accidentally stored at < −30°C due to icing of the freezer. To ensure the quality of the FFPs a battery of tests of clotting factors and inhibitors was performed. Our data demonstrate that temporary storage of FFP at temperature < −30°C does not negatively affect the quality of FFPs. The European requirement of 70% activity of factor VIII was met by all units.
After quarantine storage at > −30°C for at least 183 days fresh frozen plasma (FFP) units were stored in a deep-freezer (Kirsch, Germany). Because of icing the preset temperature of −30°C was not held over a couple of weeks, thereby possibly affecting the quality of the plasma products. The storage temperature was monitored by a temperature logger (Thermo max, Germany) and we were able to track the temperature by transferring the data via an USB cable to a personal computer. Printouts of the data revealed that the storage temperature was from −22°C until −29°C. The longest time period of FFP stored at this temperature was 92 days according to our computer-assisted documentation system.
Twenty units of FFP were thawed in a water bath for sampling of aliquots for the analysis of coagulation factors and inhibitors. Clotting assays were performed on BCS-system (Siemens, Germany) according to manufacturer's instructions.
MS-Excel statistics software (version 7.0, Microsoft, Redmond, WA, USA) was used for data analysis and presentation. Data are presented as mean ± standard deviation.
RESULTS AND DISCUSSION
Tested FFP units showed average levels of activities of more than 70% (Figure 1). Factor VIII (F VIII) is used as a marker of FFP quality according to national and European guidelines.1,2 The rationale for using F VIII is that F VIII is one of the most labile coagulation factors in plasma, therefore it is assumed that if levels of F VIII in the final product are satisfactory, the storage condition is not likely to have been inadequate. As there are no single factor concentrates available for factor V and factor XI it is important that the activities of the products are sufficient to provide enough coagulation potential for patients suffering from factor V or XI deficiency. Our data clearly show that even for those patients the activity is efficient even after a temporary storage above −30°C.
German guidelines require a storage temperature at below −30°C with a deviation of 3°C while European guidelines are less stringent with a temperature at below −25°C for a storage time of 36 months.1,2 We conclude that temporary storage of FFP above −25°C has no negative impact on the quality of clotting factors and inhibitors.