Factor VIII Inhibitor Panel

Also known as: FVIII Bethesda Inhibitor, Factor VIII Inactivity, Inhibitor APTT, Factor 8 Inhibitor Evaluation

Clinical Use

Use

The Factor VIII Inhibitor Panel (test code 40083) is used to detect and quantify inhibitors (alloantibodies or autoantibodies) against factor VIII, which may occur in patients with congenital hemophilia A undergoing replacement therapy or in acquired hemophilia. Low factor VIII activity triggers reflex testing: a chromogenic IgG antibody screen and, if positive, quantification by the Nijmegen‑Bethesda assay to determine inhibitor titer in Bethesda Units (BU), reflecting the functional inhibitory activity.

Special Instructions

Not provided.

Limitations

Not provided.

Test Details

Methodology

Immunoassay (ELISA)

Biomarkers

Factor VIII activity (aPTT‑based 1‑stage clotting assay)

Analyte

Residual clotting activity

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

IgG chromogenic antibody screen

Analyte

Screen result

Other • Binary (Detected / Not Detected)

Inhibitor titer (Nijmegen‑Bethesda assay)

Analyte

Bethesda Units

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Result Turnaround Time

1-4 days

Specimen

Plasma

Volume

two–three 2 mL platelet‑poor plasma

Minimum Volume

two–three 1 mL platelet‑poor plasma

Container

Light Blue (Sodium Citrate) tube

Collection Instructions

Collect three–four 1.8 mL or two–three 2.7 mL blood in light blue‑top sodium citrate tube; centrifuge to obtain platelet‑poor plasma (free of platelets <10,000/mcL), freeze immediately; plasma must be frozen for transport.