The stability of factor VIII in heparinized plasma.
We studied the stability for 24 hr of factor VIII:C and factor VIII C:Ag in plasma collected in citrate, EDTA or heparin, and confirmed the previously reported two-phase decay of factor VIII:C in plasma when calcium ions have been chelated. We observed that plasma factor VIII:C is remarkably stable at 22 degrees C (+/- 2 degrees) when normal calcium ion concentrations are maintained. The loss of activity of factor VIII:C between one and 24 hr after blood collection was on average only 0.5% per hr for heparinized plasma. There was also an apparent loss of factor VIII C:Ag in plasma where calcium ions had been removed, compared with factor VIII C:Ag in heparinized plasma. However, a comparison of one-site and two-site assays suggested that calcium chelating agents may lead to factor VIII C:Ag levels being under-estimated when one-site fluid-phase assays are employed. To confirm the action of calcium ions in maintaining factor VIII:C stability, we carried out a series of experiments where calcium chloride was added four hr after blood collection to plasma anticoagulated by a mixture of citrate plus heparin; we observed total recovery of factor VIII:C activity within four hr. The stability of factor VIII:C, even at room temperature, in the presence of physiological calcium ion concentrations has implications for manufacturers of factor VIII concentrates and cryoprecipitates.
D000941:Antigens / Q000032:analysis*; D001777:Blood Coagulation / Q000187:drug effects*; D002118:Calcium / Q000097:blood; D002951:Citrates / Q000097:blood; D019343:Citric Acid; D004355:Drug Stability; D004492:Edetic Acid / Q000097:blood / Q000494:pharmacology; D005169:Factor VIII / Q000032:analysis / Q000276:immunology*; D006493:Heparin / Q000097:blood* / Q000494:pharmacology; D006801:Humans; D007700:Kinetics
D000941:Antigens; D002951:Citrates; D019343:Citric Acid; D005169:Factor VIII; D006493:Heparin; D004492:Edetic Acid; D002118:Calcium