Multicenter performance evaluation and reference range determination of a new one-stage factor VIII assay.

Introduction: We conducted a multicenter evaluation of a new one-stage factor VIII (FVIII) assay (Roche Diagnostics), intended for the quantitative assessment of FVIII activity. We evaluated the analytical performance of the FVIII assay on the cobas t 711 analyzer.

Methods: Experiments performed at three laboratories used 3.2% citrated residual or commercially purchased plasma samples. 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 (vs Coagulation FVIII Deficient Plasma/Dade Actin FS Activated PTT reagent/Standard Human Plasma Calibrator on the Sysmex CS-5100 analyzer; Siemens Healthineers) 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.

Results: Across sites, SDs for repeatability were 0.016-0.046 for samples with ≤1.0 international units (IU)/dL FVIII activity; CVs were 0.9%-3.8% for samples with >1.0 IU/dl activity. Among samples with mean FVIII activity 0.344-133 IU/dl, good intermediate precision (SD 0.020 for samples with 0.344 IU/dl activity; CV 1.8%-4.7%) and good total reproducibility (CV 2.0%-13.3%) were observed. The FVIII assay showed excellent lot-to-lot variability (Pearson's r = .999) and good correlation with the comparator assay (Pearson's r = .993-.996). The reference range for FVIII activity was 82.2-218.0 IU/dl.

Conclusion: The one-stage FVIII assay demonstrated robust analytical performance on the cobas t 711 analyzer, supporting its use in routine laboratory practice.