Thai national reference preparation in blood coagulation. IV. Home made reference plasma for von Willebrand's factor...

Two lots of home made reference plasma: FVIII R:Ag 30/8/88 and FVIII R:Ag 18/10/88 were prepared by lyophilization of pooled normal human plasma. Modification of J. Cejka's technique was used to determine FVIII R:Ag. This technique was tested for reliability i.e. precision, reproducibility and sensitivity. The concentration of FVIII R:Ag, determined by calibration against the 1st British Standard for FVIII R:Ag, human 66/355, which was established by National Institute for Biological Standard and Control (NIBS & C), London, the WHO International Laboratory for Biological Standard, were respectively 1.058 and 1.023 Ag units/ml for FVIII R:Ag 30/8/88 and FVIII R:Ag 18/10/88, respectively. The precision of the procedure and the accuracy of FVIII R:Ag concentration of both lots were verified by using them as standard curve to determine FVIII R:Ag in 4 unknown plasma samples, supplied by the UK Reference Laboratory for Anticoagulant Reagent & Control; WHO Collaborating Center for Quality Assessment, in Blood Coagulation Testing for International Quality Control Survey in Blood Coagulation. The results were very satisfactory. The coefficient of variation was between 2.22-5.47 per cent when compared with other 29 laboratories around the world. These home made reference preparation are stable at least up to 30 months at -70 degrees C, and can be applied for calibration of unknown sample instead of the 1st British Standard for FVIII R:Ag, human 66/355.