Measurement of fibrinogen in frozen plasma.

Several large studies have compared fibrinogen measurements determined over a particular time interval. These assays are subject to difficulties encountered by all laboratories on tests carried out over a period of time such as assay drift. To avoid this problem, plasma can be stored frozen and fibrinogen determined in a large number of samples simultaneously. However, a thorough comparison of measurements carried out in fresh and frozen plasma has not yet been performed. Fibrinogen concentration was therefore determined in fresh plasma samples and then at a later date in the same samples after storage at -70 degrees C. A good correlation was observed between the two measurements, however, bias increased at the higher fibrinogen levels which are most critical in the determination of thrombotic risk. An increase in measurement error as a result of freezing was also observed. These effects may, therefore, be important considerations in future studies of this nature.