Reliability of "standard" plasmas used by clinical laboratories for one-stage factor VIII assays

The reliability of "standard" plasmas used by clinical laboratories to assay factor VIII concentrations of patients' plasmas was studied by assessing the credibility of their reference values. Two of three commercial reference plasmas were considered to be unreliable. The third commercial reference plasma appeared to be suitable when assayed against frozen pools of fresh normal plasma with an assigned value of 100% activity. However, assays using fresh pools of normal plasma suggested that the reference value may lack credibility. This study also showed that assignment of 100% activity to frozen pools of fresh normal plasma prepared locally in laboratories may be fallacious.