Impact of emicizumab on labs
| Lab . | Impact of emicizumab . | Recommended alternative . |
|---|---|---|
| aPTT | False decrease | Do not use while on emicizumab |
| One-stage FVIII (PTT based)* | False increase | Chromogenic FVIII with bovine reagents (measure infused and/or endogenous FVIII) |
| FVIII inhibitor titer with clotting-based assays (Bethesda) | Uninterpretable | Chromogenic Bethesda assay with bovine reagents |
| Activated clotting time (ACT) | False decrease | Anti-Xa activity |
| Activated protein C resistance (aPTT based) | Uninterpretable | Factor V Leiden genetic testing (if clinically appropriate) |
| Lab . | Impact of emicizumab . | Recommended alternative . |
|---|---|---|
| aPTT | False decrease | Do not use while on emicizumab |
| One-stage FVIII (PTT based)* | False increase | Chromogenic FVIII with bovine reagents (measure infused and/or endogenous FVIII) |
| FVIII inhibitor titer with clotting-based assays (Bethesda) | Uninterpretable | Chromogenic Bethesda assay with bovine reagents |
| Activated clotting time (ACT) | False decrease | Anti-Xa activity |
| Activated protein C resistance (aPTT based) | Uninterpretable | Factor V Leiden genetic testing (if clinically appropriate) |
The one-stage FVIII activity will overestimate the impact of emicizumab and will not be able to separate the endogenous FVIII activity from the impact of emicizumab on the assay. Emicizumab impacts all single-factor assays that are performed with one-stage, aPTT-based assays (such as factor IX activity).