New One-Stage Factor VIII Assay Evaluated

Factor VIII (FVIII) is a multi-domain glycoprotein that is synthesized in the liver. As an essential blood coagulation protein required for normal hemostasis, FVIII circulates in plasma at normal concentrations of around 50–150 international units (IU)/dL in a non-covalent complex with von Willebrand factor.

FVIII is activated to factor VIIIa via limited proteolysis by thrombin and then acts as a cofactor to activated factor IX, during the activation of factor X to factor Xa, ultimately leading to clot formation. Deficiency of or dysfunctional FVIII leads to a bleeding diathesis of varying severity, depending on FVIII levels and/or activity.

Hematologists at the Sheffield Haemophilia and Thrombosis Centre (Sheffield, UK) and their international colleagues conducted a multicenter evaluation of a new one-stage factor VIII (FVIII) assay (Roche Diagnostics, Rotkreuz, Switzerland), intended for the quantitative assessment of FVIII activity. The team evaluated the analytical performance of the FVIII assay on a Roche analyzer.

Anonymized human 3.2% citrated plasma samples, both fresh and frozen to reflect routine laboratory practice, were used throughout the study. FVIII activity was assessed using the new one-stage FVIII assay on the cobas t 711 analyzer. Five human plasma pools and two controls were used to determine assay within-run and within-laboratory precision, and total reproducibility; coefficients of variation (CVs) and/or standard deviations (SDs) were calculated. Lot-to-lot variability and method comparison versus Coagulation FVIII Deficient Plasma/Dade Actin FS Activated PTT reagent/Standard Human Plasma Calibrator on the Sysmex CS-5100 analyzer (Milton Keynes, UK) and were evaluated by Passing–Bablok and Deming regression, respectively, and Pearson's r calculated. Assay-specific reference range was determined using 199 fresh plasma samples from healthy adults, not receiving anticoagulants.

The investigators reported that the method comparisons were conducted at three international sites across the primary measuring range of both the new one-stage FVIII assay on the cobas t 711 analyzer and reference comparator assay on the Sysmex CS-5100 analyzer. Good agreement between the new one-stage FVIII assay and comparator assay was observed at three different sites. Among apparently healthy individuals, FVIII activity ranged from 82.2 to 218.0 IU/dL in fresh samples and from 79.8 to 211.0 IU/dL in frozen samples.

The authors concluded that the new one-stage FVIII assay demonstrated robust analytical performance on the cobas t 711 analyzer, supporting its use in routine laboratory practice. The study was published on March 11, 2022 in the Journal of Clinical Laboratory Analysis.

Related Links:
Sheffield Haemophilia and Thrombosis Centre 
Roche Diagnostics 
Sysmex 

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