laboratory diagnostic - coagulation - Factor XII, Hageman, activity, citrated plasma 2ml. The plasma must be frozen within 1 hour after collection and must be sent in the frozen samples container. The factors VIII, IX, XI,XII (aPTT factors) assay requires at least 2 mL of citrated plasma frozen at -20°C., Chronometric, ssso, todylaboratories®, bmn, code L16LD1568