Factor Assay

General Information

Test Availability:

Queen Elizabeth site: All Factor Assays

Heartlands site: Factor VIII only. Samples received for other factor assays will be sent to the Queen Elizabeth laboratory.

For urgent special coagulation assay information click Here

External Requests:

Note: For external requests please click Here for Coagulation Disorders request form. Please complete all information fully.

Sample packing and transportation:

Frozen plasma should be sent on dry ice using an insulated container to ensure that it remains frozen during transport. Please refer to the preanalytical variables section of the BSH guidelines on the laboratory aspects of assays used in haemostasis and thrombosis¹.

As an alternative the bio-freeze container system can be used to ensure samples remain frozen in transit. These have been locally validated to maintain samples at -20^oC for up to 12 hours  providing they have been preconditioned in a -80^oC freezer for 24 hours prior to use.

Disclaimer:

Please note failure to use an appropriate transit container may affect sample integrity, thus the accuracy of results cannot be guaranteed.  Furthermore, samples packaged incorrectly that arrive in a thawed state cannot be tested.

Please contact the laboratory on 0121 371 5988 (Queen Elizabeth Hospital) or 0121 424 0908 (Heartlands Hospital) if you require any further information.

1) Baker, P., Platton, S., Gibson, C., Gray, E., Jennings, I., Murphy, P., Laffan, M. and British Society for Haematology, Haemostasis and Thrombosis Task Force (2020), Guidelines on the laboratory aspects of assays used in haemostasis and thrombosis. Br. J. Haematol., 191: 347-362.

https://doi.org/10.1111/bjh.16776

Samples that meet the following criteria will not be processed:

• Haemolysed, clotted, underfilled or overfilled samples.
• Samples >12 hours old from the time of collection.
• Samples received from other hospital laboratories that have been frozen and thawed.
• Samples which fail the minimum data set.

Pre/post samples:

• All pre and post factor level requests must be clearly labelled as 'pre' and 'post' on the samples and request form. Please note a separate request form should be used for each pre and post request.
• Post samples should be taken at least 30 minutes after factor concentrate has been given. 

Assay limitations:

• PT based assays: (Factors II, V, VII and X) not affected by heparin up to 1 U/ml, haemoglobin up to 500 mg/dl, triglycerides up to 1000 mg/dl or bilirubin up to 30 mg/dl.
• APTT based assays: (Factors VIII, IX, XI and XII) not affected haemoglobin up to 500 mg/dl, triglycerides up to 1000 mg/dl or bilirubin up to 26 mg/dl.
• Chromogenic Factor VIII assay: not affected by heparin up to 1 U/ml.