PB1170 - Evaluation of nonacog beta pegol recovery in spiked samples using different APTT reagents/detection system available in Argentina.

Background: Nonacog beta pegol (N9-GP, Refixia) is a glycoPEGylated extended half-life (EHL) recombinant factor IX developed for prophylaxis and treatment in hemophilia B patients. A great variability has been reported when one stage clotting assay for FIX:C (OSA) was used to measure this recombinant FIX product. Chromogenic FIX assay (CSA) has not yet been approved in Argentina.

Aims: To investigate in three laboratories the recovery of N9-GP by OSA with 10 different aPTT reagents and three different clot detection systems in four different levels of N9-GP.

Methods: FIX:C by OSA were performed with10 different aPTT reagents: Diagnostica Stago (Cephascreen: poliphenol, C.K. Prest: kaolin, Triniclot aPTT S, Silica), Instrumentation Laboratory (APTT-SP and Synthasil: colloidal silica), Siemens Healthineers (Actin and Actin FSL: ellagic acid, Pathromtin SL: silicon dioxide) and Wiener Lab (APTTest: ellagic acid). Three coagulometer were used: ACL TOP 500, Sysmex CS-2500 and STA Compact Max. Calibration curves were performed with conventional plasma calibrator (cpCal, validated with internal control) and with a home-made specific product calibrator (hmspCal, 1.00 IU/ml). Samples: FIX immunodepleted plasma was spiked with N9-GP at four target levels: 0.05, 0.13, 0.50 and 1.00 IU/mL. Spiked samples were aliquoted and frozen at -80°C until analysis. Mean %Rec is the average recovery of all levels studied. Acceptable recovery: +/-20%(Accep), Overestimation: greater than 20%(Over), Subestimation: less than 20%(Sub).

Results: Table 1

Conclusion(s): There were differences of FIX:C in OSA when cpCal was used, some reagents overestimated and did so at all levels. According to the %Rec only cephascreen, actin FSL and APTTest ellagic (aPTT reagent used in Latinoamerican region) could be used for monitoringof treatment with N9-GP in the platforms studied. If a hmspCal was used, FIX:C by OSA were closer to the expected values for all reagent/detection system pairs used,this would be an alternative when CSA is not available.