Assays are available for all coagulation factors. Please discuss with Technical Specialist of the haemostasis laboratory, Haematology Registrar, or Haematologist.
Collection of samples for Factor VIII
- A trough level should be collected just before giving a FactorVIII dose.
- A peak level should be taken 30 minutes after the dose.
Requests for Chromogenic FVIII must be referred through a Haematologist or Haemophilia Centre.
Citrated platelet poor plasma. Minimum volume 0.5 mL.
or
- Filtered plasma is unsuitable and may lead to erroneously low results.
Normal Reference Intervals:
| Factors VIII and IX | 55 - 150% |
| All others |
50 - 200%
|
Factors
Uncertainty of measurement
VIII , IX, XI , XII
18%
II , V , VII , x , XIII
12%
- Paediatric reference intervals are age stratified and given on the result report
Unless URGENT
Factor assays are generally used to identify the cause of bleeding disorders. However, factors II, VII and VIII are included in the investigation of thrombosis.
The Chromogenic FVIII is used in suspected mild haemophilia A and not usually required for management. Requests for Chromogenic FVIII must be referred through a Haematologist or Haemophilia Centre.
Limitations of procedure:
Factor assays may be affected by sample activation or the presence of inhibitors.Interpretation:
Coagulation factors may be reduced due to defective production (congenital or acquired defects), consumption (DIC), dilution (massive transfusion), destruction (specific inhibitors), and in the case of factors II, VII, IX, or X, vitamin K deficiency/warfarin ingestion.For further information contact the Haematology laboratory (Ext 22067) or:
| Dr Nicola Eaddy | Ext 22071 | |
| Dr Peter Bradbeer | Ext 22062 | |
| Dr Anna Ruskova | Ext 22137 |