Evaluation and characterization of the certified reference materials for coagulation factor VIII and IX activity testing

Objective To evaluate and characterize the certified reference materials for coagulation factor Ⅷ (FⅧ) and factor Ⅸ (FⅨ) activity testing. Methods The homogeneity and stability of three lots of certified reference materials (F01-F03) with different factor concentrations were evaluated according to guidelines"Reference materials-general and statistical principles for certification","Guidance on evaluating the homogeneity and stability of samples used for proficiency testing"and"Technical Norm of Primary Reference Material". The certified reference materials were characterized by eight laboratories using one-stage method, which were calibrated by the coagulation standard provided by the National Institute for Biological Standards and Control (NIBSC) in UK. Results The Coefficient of Variation (CV) of homogeneity test of FⅧ activity of three lots of certified reference materials were 3.9%, 3.3% and 3.4%, respectively. While that of FⅨ activity were 3.7%, 3.0% and 1.8%, respectively. The results of one-way ANOVA showed that all certified reference materials had good homogeneity (P>0.05), and the between-bottle homogeneity uncertainties (ubb) of FⅧ and FⅨ activity were 0.5%-2.9% and 0.1%-3.9%, respectively. All certified reference materials stored in -80 ℃ remained stable in 9 months by trend analysis, and the long-term stability uncertainties(ults) of FⅧ and FⅨ activity were 0.5%-5.1% and 1.3%-4.4%, respectively. The characterization uncertainties (uchar) of FⅧ and FⅨ activity testing were 0.9%-2.4% and 1.1%-2.4%, respectively. The combined uncertainties and extended uncertainties (coverage factor k=2) were calculated. The assigned values of each lot of certified reference materials for FⅧ activity were (85±13)%, (36.0±3.4)% and (20.5±2.3)%, and that were (102±13)%, (47.8±6.9)% and (29.3±3.8)% for FⅨ activity, respectively. Conclusions The certified reference materials for FⅧ and FⅨ activity testing have good homogeneity and stability. The results of the characterization are accurate and reliable. Key words: Factor Ⅷ; Factor Ⅸ; Certified reference materials; Evaluation studies