Factor IX activity is determined utilizing an aPTT-based one-stage clotting time assay. Factor IX-depleted plasma is used as the substrate, and the clotting time with the patient plasma is compared to the clotting time of normal pooled plasma.patient with congenital deficiency of factor IX are said to be suffering from bleeding disorder: Hemophilia B. 3 mL Whole blood in 1 Blue Top (Sodium Citrate) tube. Mix thoroughly by inversion. Transport to Lab within 4 hours. If this is not possible, make PPP within 1 hour of collection as follows: Centrifuge sample at 3600 rpm for 15 min. & transfer supernatant to a clean plastic tube. Centrifuge this supernatant again at 3600 rpm for 15 mins. & finally transfer the supernatant (PPP) to 1 labelled, clean plastic screw capped vial. FREEZE IMMEDIATELY. Ship frozen. DO NOT THAW.