Measuring factor IX activity of nonacog beta pegol with commercially available one-stage clotting and chromogenic assay kits: a two-center study.
Essentials Validated assays are required to precisely measure factor IX (FIX) activity in FIX products. N9-GP and two other FIX products were assessed in various coagulation assay systems at two sites. Large variations in FIX activity measurements were observed for N9-GP using some assays. One-stage and chromogenic assays accurately measuring FIX activity for N9-GP were identified.



Background Measurement of factor IX activity (FIX:C) with activated partial thromboplastin time-based one-stage clotting assays is associated with a large degree of interlaboratory variation in samples containing glycoPEGylated recombinant FIX (rFIX), i.e. nonacog beta pegol (N9-GP). Validation and qualification of specific assays and conditions are necessary for the accurate assessment of FIX:C in samples containing N9-GP. Objectives To assess the accuracy of various one-stage clotting and chromogenic assays for measuring FIX:C in samples containing N9-GP as compared with samples containing rFIX or plasma-derived FIX (pdFIX) across two laboratory sites. Methods FIX:C, in severe hemophilia B plasma spiked with a range of concentrations (from very low, i.e. 0.03 IU mL(-1) , to high, i.e. 0.90 IU mL(-1) ) of N9-GP, rFIX (BeneFIX), and pdFIX (Mononine), was determined at two laboratory sites with 10 commercially available one-stage clotting assays and two chromogenic FIX:C assays. Assays were performed with a plasma calibrator and different analyzers. Results A high degree of variation in FIX:C measurement was observed for one-stage clotting assays for N9-GP as compared with rFIX or pdFIX. Acceptable N9-GP recovery was observed in the low-concentration to high-concentration samples tested with one-stage clotting assays using SynthAFax or DG Synth, or with chromogenic FIX:C assays. Similar patterns of FIX:C measurement were observed at both laboratory sites, with minor differences probably being attributable to the use of different analyzers. Conclusions These results suggest that, of the reagents tested, FIX:C in N9-GP-containing plasma samples can be most accurately measured with one-stage clotting assays using SynthAFax or DG Synth, or with chromogenic FIX:C assays.
Coagulation Department, Sheffield Teaching Hospitals, Sheffield, UK.
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Bowyer
Department of Clinical Chemistry, Skåne University Hospital, Malmö, Sweden.
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Hillarp
Novo Nordisk A/S, Novo Nordisk Park, Måløv, Denmark.
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Ezban
Novo Nordisk A/S, Søborg, Denmark.
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Persson
Coagulation Department, Sheffield Teaching Hospitals, Sheffield, UK.
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Kitchen
D001777:Blood Coagulation; D001780:Blood Coagulation Tests / Q000379:methods; D002138:Calibration; D005164:Factor IX / Q000737:chemistry / Q000627:therapeutic use*; D002836:Hemophilia B / Q000097:blood* / Q000188:drug therapy*; D006801:Humans; D010314:Partial Thromboplastin Time; D010949:Plasma; D011092:Polyethylene Glycols / Q000737:chemistry / Q000627:therapeutic use*; D011994:Recombinant Proteins / Q000737:chemistry / Q000627:therapeutic use; D015203:Reproducibility of Results
D011994:Recombinant Proteins; C000592276:nonacog beta pegol; D011092:Polyethylene Glycols; C093388:Mononine; D005164:Factor IX
blood coagulation test; factor IX; hemophilia B; nonacog beta pegol; poly(ethylene glycol)