Factor V inhibitor profile, comprehensive-994

Test info

  
Factor V inhibitor profile, comprehensive
  
994
  
LAB994
  
MSO
  
Bethesda titer
  
  • Activated partial thromboplastin time (aPTT)
  • Factor V activity
  • Factor V Bethesda titer
  • Prothrombin time (PT)
  • PT 1:1 mix with normal plasma
  • PT 1:1 mix with saline
  

Confirmation and characterization of factor V inhibitor

Specimen

  

The patient should not be on anticoagulant therapy

  
Sodium citrate (Na cit) plasma
  
  
6 mL (2 mL in each of three tubes)
  
  • Do not draw from an arm with a heparin lock or heparinized catheter
  • Immediatley following collection, mix sample thoroughly by gentle inverting 8 - 10 times, to prevent clotting
  
  1. Centrifuge for 10 minutes and carefully remove 2/3 of the plasma using a plastic transfer pipette, being careful not to disturb the cells.
  2. Deliver to a plastic transport tube, cap, and recentifuge for 10 minutes.
  3. Use a second plastic pipette to remove plasma, staying clear of the platelets at the bottom of the tube.
  4. Transfer 2 mL of plasma into three (3) separate Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp) labelled as Na cit plasma
  5. Freeze immediately
  

Frozen (preferred) – 30 days

Ambient – 4 hours

Refrigerated – NO

Performance

  
LabCorp Esoterix Coag Laboratory (500380): R – NX
  
Mo – Th, Sat
  
3 – 5 days
  

The factor V inhibitor (Bethesda titer) assay is performed using a prothrombin time-based system, using thromboplastin reagent.6 Serial dilutions are made of patient plasma with veronal buffered saline, then mixed with normal plasma containing close to 100% factor V activity, and are then incubated for two hours. A PT-based factor V assay using factor V-depleted plasma substrate is then performed on these incubated mixtures. Results are compared to those of incubated normal plasma. One Bethesda unit is defined as the amount of factor V inhibitor that neutralized 0.5 IU of factor V in this system. The number of serial dilutions tested is based on the anticipated level of the inhibitor.

Clinical and Interpretive info

  

Prothrombin Time / PT 1:1 NP

0 - 3 d:       10.7 - 15.6 sec

4 d - 6 m:   10.4 - 13.9 sec

7 m - 17 y:  10.1 - 12.7 sec

≥18 y:         9.6 - 11.5 sec 

APTT

0 - 3 d:       not established

4 d - 6 m:   23.1 - 32.5 sec

7 m - 17 y:  23.1 - 30.1 sec

≥18 y:        22.9 - 30.2 sec 

Factor V activity

0 - 3 d:       not established

4 d - 6 m:   34 - 108 %

≥7 m:  23.1 - 30.1 sec

Facator V inact assay

<0.8 Bethesda

Billing

  
85220
85335
85610
85611 x 2
85730

Tracking

  
02/09/2021
  
01/02/2024
  
01/02/2024