A lyophilized human reference plasma for coagulation factors. Evidence for stability of factors I, II, V, and VII...

Results are reported of a one-year study on the stability of a lyophilized normal human reference plasma, originally standardized for eight clotting factor activities against a freshly prepared pool of citrated, platelet-poor normal human plasma. The stability of any particular coagulant activity in this reagent was represented mathematically as a function of the observed clotting times obtained under specific assay conditions, where any observed change in the clotting times over the trial period was taken to reflect a change in the stability of the reference plasma. Taking into consideration estimates of variability contributed by different donors of factor-deficient substrata-plasma, different lots of substrate from the same donor, different technologists, and certain age-of-substrate lot trends, there was no statistically significant change in functional activity for Factors V and VII through XII in the reagent when it was stored unreconstituted below -25C. By less rigorous criteria, both clottable fibrinogen (Factor I) and the thrombin-forming potential of prothrombin (Factor II) also were stable during this same period. Based on these results, it was concluded that when suitably prepared, lyophilized human plasma can be used as a stable, secondary standard reference for the assay of coagulation factors.