An Improved Method of Making Factor VIII Concentrates
The yields from batch preparation of Factor VIII concentrates can be substantially improved by collecting the blood into heparin rather than into CPD as anticoagulant. The resultant cryoprecipitate contains 78 ± 9% of the original plasma activity if 20 mls of supernatant per litre of starting plasma are left with the cryoprecipitate to maintain heparin levels. This cryoprecipitate was further purified by solubilization at 37°C for 5 minutes using 40 cc of saline per litre of starting plasma. This preparation was adjusted to pH 6.3 and 4.5% PEG 4000. Then, after removal of the precipitate by centrifugaron, the 4.5% PEG supernatant is adjusted to pH 6.0 and 11% PEG. The 11% PEG precipitate obtained after centrifugation is resolubilized in 1/100th the original plasma volume with buffer (0.1 M glycine, 20 mM citrate, 0.15 H saline) containing 1 unit of heparin per ml. Experiments using plasma pools containing 1-15 donor units gave yields ranging from 390-490 plasma Factor VIII equivalents per litre of the starting plasma. The final product retains an average of 90% of the initial Factor VIII activity after 24 hours at 22°C. It is believed that the present method could substantially reduce the cost of producing Factor VIII concentrates.