Monitoring of Nonacog Beta Pegol: One-Stage Clotting Assay With Kaolin Reagent as a Practical Alternative to Chromogenic Methods.

introductionAccurate monitoring of nonacog beta pegol (N9-GP) is essential to ensure appropriate treatment and to avoid under- or overdosing, which may result in clinical complications. The product's extended half-life, achieved through molecular modification, poses challenges for activity measurement, particularly when using a one-stage clotting assay (OSA). Therefore, a chromogenic substrate assay (CSA) is preferred, although it may be less practical for urgent or routine monitoring.

aimTo evaluate OSA and CSA for N9-GP measurement, focusing on the suitability of the OSA STA CK Prest reagent on the STA R MAX analyser.

methodsFactor IX activity (FIX:C) of N9-GP in vitro spiked and post-infusion samples were measured using various OSA reagents and CSA across different analysers. The in vitro sample results were evaluated as percentage recovery; the OSA STA CK Prest results from both spiked and post-infusion samples were compared with those obtained by the CSA Biophen FIX.

resultsAcceptable recoveries for samples spiked at concentrations of 0.04, 0.08, 0.15, 0.61 and 1.22 IU/mL were achieved using CSA Biophen FIX (mean recovery 92% with the CN 3000 analyser and 108% with the STA R MAX analyser) and OSA STA CK Prest (mean recovery 92%, range 86%-111%). STA CK Prest showed FIX:C results comparable to Biophen FIX in both in vitro and post-infusion samples.

conclusionsSTA CK Prest and Biophen FIX showed acceptable recoveries for N9-GP, with FIX:C results in good agreement in both in vitro and post-infusion samples. This supports the reliability of STA CK Prest for FIX:C measurement.