Estimation of Nuwiq ® (simoctocog alfa) activity using one‐stage and chromogenic assays—Results from an international comparative field study

BACKGROUND Accurate determination of coagulation factor VIII activity (FVIII:C) is essential for effective and safe FVIII replacement therapy. FVIII C can be measured by one-stage and chromogenic substrate assays (OSAs and CSAs, respectively); however, there is significant interlaboratory and interassay variability. AIMS This international comparative field study characterized the behaviour of OSAs and CSAs used in routine laboratory practice to measure the activity of Nuwiq® (human-cl rhFVIII, simoctocog alfa), a fourth-generation recombinant human FVIII produced in a human cell line. METHODS FVIII-deficient plasma was spiked with Nuwiq® or Advate® at 1, 5, 30 and 100 international units (IU)/dL. Participating laboratories analysed the samples using their routine procedures and equipment. Accuracy, inter- and intralaboratory variation, CSA:OSA ratio and the impact of different OSA and CSA reagents were assessed. RESULTS Forty-nine laboratories from 9 countries provided results. Mean absolute FVIII:C was comparable for both products at all concentrations with both OSA and CSA, with interproduct ratios (Nuwiq® :Advate® ) of 1.02-1.13. Mean recoveries ranged from 97% to 191% for Nuwiq® , and from 93% to 172% for Advate® , with higher recoveries at lower concentrations. Subgroup analyses by OSA and CSA reagents showed minor variations depending on reagents, but no marked differences between the two products. CSA:OSA ratios based on overall means ranged from 0.99 to 1.17 for Nuwiq® and from 1.01 to 1.17 for Advate® . CONCLUSIONS Both OSAs and CSAs are suitable for the measurement of FVIII:C of Nuwiq® in routine laboratory practice, without the need for a product-specific reference standard.