Factor assays (one-stage clotting): FII, FV, FVII, FVIII, FIX, FX, FXI, FXII, PK, HMWK

Description: 
One-stage clotting assays for determining coagulation factor function are based on the ability of dilutions of patient's plasma to correct the clotting time of a plasma that has normal levels of all clotting factors except the one being measured, in which it is totally deficient. Clotting times are derived via prothrombin time reagents for factors II, V, VII & X, and APTT-derived for factors VIII, IX, XI, XII, prekallikrein and HMWK. Results are assessed from a parallel line bioassay graphical plot against that of a standard plasma.
Clinical details: 
The complex orchestration of cellular and molecular participants of haemostasis achieves a crucial yet fine balance of procoagulant and anticoagulant mechanisms. Quantitative or qualitative 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. Deficiencies of FXII, prekallikrein & high molecular weight kininogen from the so-called contact pathway are not associated with bleeding disorders but can elevate an APTT, so the assays are available as part of the repertoire to investigate elevated APTTs when necessary.
Related condition or disease: 
Haemophilias and other factor deficiencies, inhibitors, acquired factor deficiencies
Reference range: 

FII 50 - 150
FV 50 - 150
FVII 50 - 150
FVIII 50 - 150
FIX 50 - 150
FX 50 - 150
FXI 57.9 - 118.5
FXII 50 - 150
PK 50 - 150
HWMK 50 - 150

Units: 
IU/dl
Department: 
Haemostasis and Thrombosis Department
Location: 
St Thomas' Hospital
Sample type and Volume required: 
External requests: Citrated platelet poor plasma
500µL x 1 aliquot for 2 factor assays
Internal requests: please refer to EPR label

Turnaround time: 
7 - 10 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.

Criteria for acceptance / rejections of sample
Contacts:
Diagnostic Haemostasis and Thrombosis Department
St Thomas': 020 7188 2797; Guy's: 020 7188 7188 ext. 53860
St Thomas' Hospital
North Wing - 4th and 5th Floors
Westminster Bridge Road
London SE1 7EH

Laboratory opening times
24/7

Guy's Hospital
Southwark Wing - 4th Floor
Great Maze Pond
London SE1 9RT

Outside core hours, contact Duty Haemostasis Biomedical Scientist
For clinical advice or interpretation of results, please contact the laboratory in the first instance.
Laboratory: 
Diagnostic Haemostasis and Thrombosis Laboratory at Guy's and St Thomas'

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Last updated: 08/03/2017