Laboratory Test Directory

BETHESDA   [FACTOR INHIBITOR ASSAY] (089-0418)

Synonyms: Bethesda Assay

CPT 4 Code: 85335

Test Order Mnemonic: Bethesda

Applies To: Measures levels of inhibitor of a specific factor (Factor VIII)

Lab: Hematopathology

Request Form: Hematology A

Collection: Routine venipuncture; discard 1st mL of blood or collect other tubes (EDTA, red-topped) prior to collecting sample in blue-topped (citrate) tube.

Storage Instructions: Viable for 4 hours at room temperature.   If time from draw to receipt in the laboratory is to be greater than 4 hours, centrifuge the specimen; remove the plasma from red cells and snap freeze (-70°C) plasma. Snap frozen plasma is viable indefinitely.

Causes for Rejection: QNS, clotted, severely hemolyzed specimen, specimen greater than 4 hours old, identification error, sample processed and/or stored improperly.

Availability: Samples are accepted 24 hours per day at Sample Management, 5.136 McCullough Bldg.

Turnaround Time: Testing is performed on Day Shift only.  Call lab for schedule.

Special Instructions: Deliver sample to lab within ½ hour for best results. Accepted up to 4 hours from draw.

Specimen: Blood

Volume: 4.5 mL blood

Container: 3.2% Sodium citrate tube (light Blue top tube)

Reference Ranges: Normal < 0.5 units Bethesda Units

Test Method: Electromagnetic Viscosity Detection

Interfering Substances: Replacement or anticoagulant therapy, presence of lupus anticoagulant

Reviewed 5/3/2011 by W. Russo, MT(ASCP)