Reliability of laboratory tests in the presence of emicizumab
| Laboratory test . | Reliability of measuring emicizumab activity . | Reliability of measuring activity of extrinsically given FVIII concentrate . |
|---|---|---|
| aPTT | Not reliable | Not reliable |
| FVIII activity—one stage method | Not reliable—grossly overestimates hemostatic potential | Not reliable |
| FVIII activity—chromogenic method with bovine reagents | Does not measure emicizumab | Reliable method of measuring underlying intrinsic and administered FVIII activity. Unaffected by emicizumab. |
| FVIII activity—chromogenic method with human reagents | Linear correlation with emicizumab blood concentration and can be used as a surrogate to an emicizumab level | Measures underlying intrinsic and administered FVIII activity, but emicizumab will interfere |
| Emicizumab concentration | Reliable method of emicizumab concentration but not readily available | Does not measure FVIII activity |
| Laboratory test . | Reliability of measuring emicizumab activity . | Reliability of measuring activity of extrinsically given FVIII concentrate . |
|---|---|---|
| aPTT | Not reliable | Not reliable |
| FVIII activity—one stage method | Not reliable—grossly overestimates hemostatic potential | Not reliable |
| FVIII activity—chromogenic method with bovine reagents | Does not measure emicizumab | Reliable method of measuring underlying intrinsic and administered FVIII activity. Unaffected by emicizumab. |
| FVIII activity—chromogenic method with human reagents | Linear correlation with emicizumab blood concentration and can be used as a surrogate to an emicizumab level | Measures underlying intrinsic and administered FVIII activity, but emicizumab will interfere |
| Emicizumab concentration | Reliable method of emicizumab concentration but not readily available | Does not measure FVIII activity |