Imperial Collage Healthcare

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Inhibitor Screen & Bethesda Assay

Test Background

The Inhibitor Screen is used to identify the presence of immediate or time-dependent inhibitors to coagulation factors. Inhibitors may be naturally acquired in certain disease states or may develop in response to factor concentrate treatment regimens in haemophiliacs. Inhibitors may be suspected when in vivo recovery is significantly lower than expected given the dose of factor concentrate administered.
The Inhibitor Assay (Bethesda) uses the Nijmegen modification to quantify inhibitor activity in Bethesda Units (Bu), namely for factors FVIII and FIX.

Clinical Indications

Inhibitor screen: Suspicion of acquired haemophilia or following loss of efficacy post-treatment with factor concentrates.

Inhibitor Assay: Quantifying/monitoring the level of a known factor inhibitor.

Reference Range
For advice with interpretation please contact the lab or haematology clinical team.

Sample Required
4.5 mL sodium citrate (pale blue top) adults 1.8 mL sodium citrate (pale blue top) paediatrics

Turnaround Time
14 days


Please Note: Samples will be rejected if under/over-filled, clotted or haemolysed

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