Bethesda Inhibitor

Test Mnemonic


CPT Codes

  • 85335 - QTY (1)


  • Factor IX Inhibitor
  • Factor VIII Inhibitor
  • Inhibitor Assay

Performing Laboratory

Cleveland Clinic Laboratories

Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
1 mLPlasmaSodium citrate (Lt. Blue) FrozenSend two 1 mL aliquots


Environmental Condition Description
Ambient4 hours
Frozen14 days at -20 C; 6 months at -70 C

Days Performed

Mon - Fri

Turnaround Time

1 - 3 days


Name Description
Clotting Assay 

Reference Range

Bethesda Inhibitor
Sex Age From Age To Type Range Range Unit
   Years99 YearsNormal< or = 0.4Inhib Unit

Special Info

Indicate coagulation factor to be tested. 3.2% sodium citrate is the preferred anticoagulant recommended by NCCLS. If inhibitor to porcine Factor VIII is needed, please supply porcine Factor VIII with patient sample. Appropriate factor assay should also be ordered when requesting a Bethesda inhibitor.

Clinical Info

Factor VIII inhibitor: Factor VIII inhibitors most commonly occur in patients with Factor VIII deficiency (Hemophilia A) after treatment with factor replacement. Factor VIII inhibitors can also arise de novo in the elderly in a patient with lymphoproliferative disorders, post-partum and a patient with automimmune disorders.Factor IX inhibitor: Most commonly occurs in a patient with Factor IX deficiency (Hemophilia B) after treatment with factor IX replacement. De novo Factor IX inhibitors can occur but are rare. Porcine Factor VIII Inhibitor: Useful to determine the cross reactivity of factor VIII inhibitor against porcine factor VIII. If a factor VIII inhibitor is suspected, this assay should be ordered in addition to Factor VIII inhibitor level if porcine factor VIII is a therapeutic option. Factor VIII inhibitor: Inhibitor titers < 5 Bethesda units are considered low titer inhibitors; those > or = 5 Bethesda units are considered high titer inhibitors. Porcine Factor VIII inhibitor: A high titer (> 5 Bethesda units) against Porcine Factor VIII may make Porcine Factor VIII ineffective as a potential therapy for a Factor VIII inhibitor.