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

ABSTRACT

Two lots of home made reference plasma FVIII RAg 30/8/88 and FVIII RAg 18/10/88 were prepared by lyophilization of pooled normal human plasma. Modification of J. Cejka's technique was used to determine FVIII RAg. This technique was tested for reliability i.e. precision, reproducibility and sensitivity. The concentration of FVIII RAg, determined by calibration against the 1st British Standard for FVIII RAg, 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 RAg 30/8/88 and FVIII RAg 18/10/88, respectively. The precision of the procedure and the accuracy of FVIII RAg concentration of both lots were verified by using them as standard curve to determine FVIII RAg 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 RAg, human 66/355.