Factor antigen assays: FII, FV, FVII, FVIII, FIX, FX, FXI

Coagulation factor deficiencies can be quantitative, involving a reduced concentration of a normally functioning molecule, or qualitative, involving dysfunctional molecules but typically normal concentration, or at least a higher concentration than that indicated from biological activity alone. Coagulation factor antigen assays are sandwich ELISAs that measure concentration irrespective of function. The coagulation factor being measured is captured by antibodies bound to microtitre plate wells, incubated, and unbound material then washed off. A solution of antibody to the coagulation factor that is conjugated to an enzyme is added to ‘tag’ onto any captured coagulation factor. Unbound conjugate is washed off and a substrate for the enzyme is added, the product of the enzyme-substrate reaction being coloured. Colour intensity is in direct proportion to the degree of conjugate-binding, itself proportional to the amount of coagulation factor capture and thus, concentration.
Clinical details: 
The complex orchestration of cellular and molecular participants of haemostasis achieves a crucial yet fine balance of procoagulant and anticoagulant mechanisms. Deficiency of a procoagulant integral to the molecular interplay converging on fibrin formation reduces ability to form clots and can give rise to a bleeding disorder.
Reference range: 

FII 81.5 - 141.0
FV 73.8 - 141.0
FVII 50.0 - 139.6
FVIII 54.5 - 137.6
FIX 77.7 - 125.2
FX 72.5 - 119.6
FXI 74.4 - 126.0

Sample type and Volume required: 
External requests: Citrated platelet poor plasma
375µL x 1 aliquot for each assay
Internal requests: please refer to EPR label

Turnaround time: 
14 - 21 days
Special sample instructions: 

The samples should be analysed or manipulated & stored in the laboratory within 4 hours of venepuncture. Please ensure sample tubes are filled exactly to the fill-line as underfilling creates a dilution error and leads to inaccurate results.

Diagnostic Haemostasis and Thrombosis Department
020 7188 2797
St Thomas' Hospital
North Wing - 4th and 5th Floors
Westminster Bridge Road
London SE1 7EH

Laboratory opening times
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 08/03/2017