Anti-Xa Assay

General Information

Test Availability:

Queen Elizabeth and Heartlands sites: LMWH

Queen Elizabeth site only: UFH, Apixaban, Rivaroxaban, Fondaparinux

Heartlands site only: Edoxaban

Samples received at each site will be sent on to the appropriate laboratory for testing.

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.

Assay Limitations:

• For accurate results samples should be collected 3-4 hours post dose, when the concentration in the blood is expected to be at peak level.
• Random and trough anti-Xa tests may also be requested when there are concerns that the anticoagulant may be accumulating e.g. in renal failure.
• If heparin is being given by continuous venous infusion, samples can be taken at any time but they must be taken from the other arm.

Notes

Please state anticoagulant on request form e.g. LMWH, UFH, Apixaban, Rivaroxaban, Fondaparinux or Edoxaban. Samples must be collected 4 hours post dose.

LMWH: Samples should be taken 4 hours after subcutaneous injection, once steady state has been achieved after administration of at least three doses.