Table 3.
Ratio of chromogenic substrate to one-stage assay results depend on FVIII level
| Label activity, IU mL−1 | Mean ratio CS (n = 11 labs)/OS (n = 30 labs) | Mean CS/OS ratio at individual labs (n = 11*) | Range of CS/OS ratios at individual labs (n = 11*) | |
|---|---|---|---|---|
| Advate® | 0.80 | 1.12 | 1.12 | 0.81–1.78 |
| 0.20 | 1.02 | 1.07 | 0.48–1.61 | |
| 0.05 | 0.86 | 1.00 | 0.58–1.60 | |
| rFVIIIFc | 0.87 | 1.26 | 1.27 | 0.87–2.18 |
| 0.22 | 1.26 | 1.37 | 0.59–2.63 | |
| 0.054 | 1.04 | 1.24 | 0.65–2.08 |
rFVIIIFc, recombinant factor VIII Fc fusion protein; CS, chromogenic substrate assay; OS, one-stage clotting assay.
*
Eleven of 30 participating laboratories performed both the one-stage and chromogenic substrate assays.