The statistical process control required under International Organization for Standardization 15189 as well as economic considerations necessitates having robust methods that do not need systematic recalibration for each series of analyses. Using the concrete example of one-stage clotting factor VIII assay, we assessed the analytic variability specifically linked to changing factor VIII deficient plasma vials. The study used freeze-dried (Instrumentation Laboratory, Siemens, Stago and T-Coag) and frozen (Affinity Biologicals and Precision Biologic) factor VIII deficient plasmas. On the most widely recognized acceptability criteria and methods (i.e. those of Kallner et al. and Kasper et al.), the Stago and Instrumentation Laboratory plasmas require systematic recalibration at each vial changeover.