Rox Factor IX is a chromogenic assay kit based upon FXa generation for the determination of Factor IX (FIX) activity in FIX preparations, including potency assignment of FIX concentrates.
For determination of Factor IX activity in plasma and Factor IX preparations, including potency assignment of FIX concentrates.
- No use of FIX deficiency plasma
- Detection Limit: 0.1% FIX (CLSI EP17-A)
- Quantification Limit: 0.5% FIX (CLSI EP17-A)
- Linearity: 0.5 – 200% (CLSI EP06-A)
- Reagent A (2 vials)
Reagent A contains lyophilized human FVIII and human FX. Reconstitute with 1.4 ml water. Allow to stand for 5 min at 20-25°C with intermittent gentle mixing for complete reconstitution.
- Reagent B (2 vials)
Reagent B contains lyophilized bovine FXIa, calcium chloride and phospholipids. Reconstitute with 8.0 mL water. Allow to stand for 5 min at 20-25°C with intermittent gentle mixing for complete reconstitution.
- FXa Substrate, 5 mL (1 vial)
Liquid solution of chromogenic FXa substrate (Z-D-Arg-Gly-Arg-pNA), 2.5 mmol/l, containing a thrombin inhibitor. Ready to use.
- FIX Diluent Buffer, Stock Solution, 20 mL (1 vial)
Liquid stock solution of diluent buffer. Before use, dilute 1 + 9 with water to obtain a 0.025 mol/l Tris-HCl buffer working solution, pH 7.9, with 1% bovine serum albumin.
Note: All reconstitutions and dilutions should be made with water of a quality of at least NCCLS Type II water.
FIX activity is determined in a chromogenic method, in which human FIX is activated by bovine FXIa and where formed FIXa activates human FX in the presence of human FVIII, calcium ions and phospholipid. Similar to in vivo conditions, FVIII is activated by thrombin which is generated during the incubation. The amount of FXa formed is determined from the hydrolysis of a chromogenic FXa substrate. The FIX activity of the sample is assigned vs. a FIX concentrate standard with FIX potency expressed in International Units (IU).
FIX activity in plasma and concentrates is currently determined with clotting methods. The accuracy may be compromised due to low-resolution dose-response curves. New rFIX variants may be a challenge regarding suitability of clotting methods. Read more…